Fisheries and Aquaculture: Volume 9 (The Natural History of the Crustacea) [1 ed.] 0190865628, 9780190865627

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Fisheries and Aquaculture

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The Natural History of the Crustacea Series SERIES EDITOR Martin Thiel EDITORIAL ADVISORY BOARD Geoff Boxshall, Natural History Museum, London, UK Emmett Duffy, Virginia Institute of Marine Sciences, Gloucester, USA Darryl Felder, University of Louisiana, Lafayette, USA Gary Poore, Victoria Museum, Melbourne, Australia Bernard Sainte-​Marie, Fisheries and Oceans Canada, Mont-​Joli, Canada Gerhard Scholtz, Humboldt University Berlin, Berlin, Germany Fred Schram, Friday Harbor Marine Laboratory, Seattle, USA Les Watling, University of Hawaii, Hawaii, USA Functional Morphology and Diversity (Volume 1) Edited by Les Watling and Martin Thiel Lifestyles and Feeding Biology (Volume 2) Edited by Martin Thiel and Les Watling Nervous Systems and Control of Behavior (Volume 3) Edited by Charles Derby and Martin Thiel Physiology (Volume 4) Edited by Ernest S. Chang and Martin Thiel Life Histories (Volume 5) Edited by Gary Wellborn and Martin Thiel Reproductive Biology (Volume 6) Edited by Rickey Cothran and Martin Thiel Developmental Biology and Larval Ecology (Volume 7) Edited by Klaus Anger, Steffen Harzsch, and Martin Thiel Evolution and Biogeography (Volume 8) Edited by Gary Poore and Martin Thiel Fisheries and Aquaculture (Volume 9) Edited by Gustavo Lovrich and Martin Thiel

Fisheries and Aquaculture The Natural History of The Crustacea Volume 9

EDITED BY GUSTAVO LOVRICH AND MARTIN THIEL

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1 Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and certain other countries. Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America. © Oxford University Press 2020 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by license, or under terms agreed with the appropriate reproduction rights organization. Inquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above. You must not circulate this work in any other form and you must impose this same condition on any acquirer. Library of Congress Cataloging-​in-​Publication Data Names: Lovrich, Gustavo A., editor. | Thiel, Martin, 1962–​editor. Title: Fisheries and aquaculture /​edited by Gustavo Lovrich and Martin Thiel. Description: New York, NY : Oxford University Press, [2020] | Series: The natural history of the crustacea ; volume 9 | Includes bibliographical references and index. Identifiers: LCCN 2019054257 (print) | LCCN 2019054258 (ebook) | ISBN 9780190865627 (hardback) | ISBN 9780197517390 (epub) | ISBN 9780197517406 (oso) Subjects: LCSH: Crustacea. | Shellfish fisheries. | Shellfish culture. Classification: LCC SH379.6 .F57 2020 (print) | LCC SH379.6 (ebook) | DDC 639/​.4—​dc23 LC record available at https://​lccn.loc.gov/​2019054257 LC ebook record available at https://​lccn.loc.gov/​2019054258 9 8 7 6 5 4 3 2 1 Printed by Integrated Books International, United States of America

CONTENTS

Preface • vii Acknowledgments • ix Contributors • xi

1. Crustaceans as Fisheries Resources: General Overview  •  1 Caleb Gardner, Reginald A. Watson, Anes Dwi Jayanti, Suadi, Mohsen AlHusaini, and Gordon H. Kruse



2. Crab Fisheries  •  21 Bradley G. Stevens and Thomas J. Miller



3. Lobster Fisheries  •  55 Richard A. Wahle, Adrian J. Linnane, and Amalia M. Harrington



4. Shrimp Fisheries  •  91 Raymond T. Bauer



5. Squat Lobster Fisheries  •  117 Mariano J. Diez



6. Krill Fishery  •  137 So Kawaguchi and Stephen Nicol



7. Marginal Marine Crustacean Fisheries  •  159 Boris A. López



8. Inland Crustacean Fisheries  •  181 Miles Abadilla, W. Ray McClain, Taku Sato, Luis M. Mejía-​Ortíz, and Miguel A. Penna-​Díaz



9. Freshwater Caridean Culture  •  207 Wagner C. Valenti and Dallas L. Flickinger

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10. Penaeid Shrimp Aquaculture  •  233 Claude E. Boyd and Lauren N. Jescovitch



11. Crayfish Aquaculture  •  259 W. Ray McClain



12. Aquaculture of Marine Lobsters  •  285 Andrew Jeffs, Carly Daniels, and Kevin Heasman



13. Marine Ornamental Decapods—​Collection, Culture, and Conservation  •  313 Ricardo Calado



14. Planktonic Crustacean Culture—​Live Planktonic Crustaceans as Live Feed for Finfish and Shrimps in Aquaculture  •  341 Per Meyer Jepsen, Kristian Syberg, Guillaume Drillet, and Benni Winding Hansen



15. Ecological Factors in the Emergence of Pathogens in Commercially Important Crustaceans • 367 Jeffrey D. Shields and Juan Pablo Huchin-​Mian



16. Parasitic Crustaceans  •  401 Barbara F. Nowak, Melissa B. Martin, and Sebastián Boltaña



17. Marine Crustaceans as Bioindicators: Amphipods as Case Study  •  435 Carlos Navarro-​Barranco, Macarena Ros, José M. Tierno de Figueroa, and José M. Guerra-García



18. Crustaceans Used in Biotechnology  •  463 María Cecilia Gortari and Roque Alberto Hours



19. Management and Handling of Commercial Crustaceans  •  495 Adam Powell, Sara Barrento, and Daniel M. Cowing Index • 525

PREFACE

This is the ninth volume of a ten-​volume series on The Natural History of the Crustacea. Our volume examines Fisheries and Aquaculture, and it follows Volume 1: Functional Morphology and Diversity, Volume 2: Life Styles and Feeding Biology, Volume 3: Nervous Systems and Control of Behavior, Volume 4:  Physiology, Volume 5:  Life Histories, Volume 6:  Reproductive Biology, Volume 7:  Developmental Biology and Larval Ecology, and Volume 8: Evolution and Biogeography. The remaining volume will explore additional aspects of crustacean ecology and conservation biology. Chapters in this volume synthesize our current understanding of the diverse topics in fisheries and aquaculture. In the first part of the book we explore worldwide crustacean fisheries. Caleb Gardner and collaborators offer a general introduction about crustaceans as a global fisheries resource. Bradley Stevens and Thomas Miller detail crab fisheries and its principal exploited species, management systems, and sustainability of these fisheries, while Richard Wahle and collaborators explore lobster fisheries for the families Palinuridae, Nephropidae, and Scyllaridae, commonly known as spiny, clawed, and slipper lobsters, respectively, their fishery status, and management. Raymond Bauer explains aspects related to shrimp fisheries, including shrimp as a valuable protein source for humans, bycatch, and ecological problems such as the destruction of the seafloor by bottom trawling, fishery management, and the decisions required to achieve sustainable shrimp fisheries. Mariano Diez focuses on the main species exploited in squat lobster fisheries, their use for human consumption and as food in salmon aquaculture, and their role in coastal ecosystems. This first part of the volume concludes with two chapters on harvested crustaceans that are usually not within the focus of the mainstream fisheries research, possibly because they are caught by local fishing communities in small-​scale operations and sold locally as subsistence activity. So Kawaguchi and Stephen Nicol focuses in fisheries for krill, the most abundant metazoan on Earth. Biological and ecologic aspects are mentioned, demostrating how climate change is affecting the krill populations. The authors also review the current managing of the industry due to the participation of international regulation commisions. Boris López showcases several marginal fisheries of nondecapod crustaceans, such as intertidal barnacles from coastal upwelling systems, stomatopods sold in Asian fish markets and in the Mediterranean, and even beach-​dwelling sand hoppers, used as pet food. Miles Abadilla and collaborators provide an overview of the main crustacean fisheries from inland habitats, such as lakes, rivers, and swamps. In the second part of the book, the authors explore the variety of cultured crustacean species. Wagner Valenti and Dallas Flickinger present culture advances of freshwater carideans, including Macrobrachium rosenbergii and others. Claude Boyd and Lauren Jescovitch show that most penaeid

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viii Preface aquaculture production is based on two species that are major commodities in the international trade; they also highlight the environmental and sanitary concerns of this practice of production. The chapter by W. Ray McClain provides a concise overview of crayfish aquaculture from all continents, done at extensive or semiextensive levels of production. Andrew Jeffs and collaborators evaluate advances in lobster culture, whether for restocking wild populations, human consumption, or as ornamental animals. Ricardo Calado describes the culture of marine ornamental decapods, their collection, packing and shipping, and conservation; he also introduces important aspects of broodstock husbandry and maturation, larviculture, and grow-​out to commercial size. Finally, Per Meyer Jepsen and collaborators illustrate the enormous potential of cultivating planktonic crustacean as live food for aquaculture or aquarium industries, highlighting the technological advances and challenges in the culture of Artemia, cladocerans, and copepods. The chapters of the third part of the volume focus on important challenges and opportunities, including diseases and parasitism, the use of crustaceans as bioindicators, and their role in biotechnology. Jeffrey Shields and Juan Pablo Huchin-​Mian review the main causal factors involved in the emergence, transmission, and spread of disease agents in commercially important crustaceans by focusing on the ecological factors that lead to outbreaks. Barbara Nowak and collaborators describe the biology, effects, epidemiology of the infections, and economic impacts of parasitic crustaceans, such as sea lice (copepods), isopods, and pea crabs, that affect other commercial species. How crustaceans can be used as bioindicators is explored in the chapter by Carlos Navarro-​Barranco and collaborators; given their expertise, they focus on amphipods, especially caprellids, as indicators for water quality. María Gortari and Roque Hours describe the use of crustaceans in biotechnology to produce biomaterials like chitin and its derivatives (chitosan, chito-​oligosaccharides, and glucosamine), proteins, lipids, and carotenoid pigments. These compounds have enormous potential for multiple applications in the food, pharmaceutical, textile, biomedical, and agricultural industries as well as in bio-​and nanotechnology. Finally, Adam Powell and collaborators present a primer on the management and handling of commercial crustaceans from both wild-​caught fisheries and the aquaculture industry and what is needed to ensure successful live transport to processing factory lines or fish markets; they detail the procedures involved in each stage of care and handling of the crustaceans, including regular sampling for quality assurance, as well as ethical considerations for animal welfare and disease regulations. Collectively, these 19 chapters provide a thorough exposition of the present knowledge across the major themes in crustacean fisheries and aquaculture. We expect that this volume will be valuable to scholars and students of fisheries and aquaculture related to crustaceans and hope its syntheses and thoughtful overview will be a valuable resource for managers of crustacean fisheries and administrators of crustacean culture centers.

ACKNOWLEDGMENTS

We thank our contributors for graciously sharing their time, energy, knowledge, and insights in order to make this volume possible—​it has been both a pleasure and an honor to work with each of them. Our editorial assistants, Annie Mejaes, Mika Tan, Tim Kiessling, Miles Abadilla and Miguel Angel Penna-Díaz, were impeccably skilled and organized and always kept us moving forward. We thank our external reviewers for their valuable and generous feedback. Finally, we express our appreciation to our publisher, Oxford University Press, for its commitment to this project. Editing of this book was generously supported by Universidad Católica del Norte, Chile.

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CONTRIBUTORS

EDITORS Gustavo Lovrich Centro Austral de Investigaciones Científicas (CADIC-CONICET) Ushuaia, Argentina Martin Thiel Facultad Ciencias del Mar Universidad Católica del Norte Coquimbo, Chile AUTHORS Miles Abadilla Facultad Ciencias del Mar Universidad Católica del Norte Coquimbo, Chile Mohsen AlHusaini Kuwait Institute for Scientific Research KISR Ecosystem-​Based Management of Marine Resources Program Kuwait City, Kuwait Sara Barrento Biosciences Department Centre for Sustainable Aquatic Research Swansea University West Sussex, England, United Kingdom CIIMAR–​Interdisciplinary Centre of Marine and Environmental Research Matosinhos, Portugal Coastal Biodiversity Group

University of Porto Porto, Portugal Raymond T. Bauer Department of Biology University of Louisiana Lafayette, LA, United States of America Sebastián Boltaña Departamento de Oceanografía Universidad de Concepción Concepción, Chile Claude E. Boyd School of Fisheries, Aquaculture and Aquatic Sciences Auburn University Auburn, AL, United States of America Ricardo Calado Departamento de Biología CESAM and ECOMARE Universidade de Aveiro Aveiro, Portugal Daniel M. Cowing NAFC Marine Centre Port Arthur, Shetland, United Kingdom Department of Marine Science and Technology University of the Highlands and Islands Inverness, Scotland, United Kingdom xi

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xii Contributors Carly Daniels The National Lobster Hatchery Cornwall, England, United Kingdom Mariano J. Diez Centro Austral de Investigaciones Científicas (CADIC-​CONICET) Ushuaia, Argentina Guillaume Drillet Environment Health and Safety Singapore, Singapore Dallas L. Flickinger Aquaculture Center (CAUNESP) UNESP - São Paulo State University São Paulo, Brazil José M. Guerra-García Laboratorio de Biología Marina Departamento de Zoología Facultad de Biología Universidad de Sevilla Sevilla, Spain Caleb Gardner Institute for Marine and Antarctic Studies University of Tasmania Hobart, TAS, Australia College of Economics and Management Shanghai Ocean University Shanghai, China María Cecilia Gortari CINDEFI–​Centro de Investigación y Desarrollo en Fermentaciones Industriales Universidad Nacional de La Plata Buenos Aires, Argentina Benni Winding Hansen Department of Science and Environment Roskilde University Roskilde, Denmark Amalia M. Harrington School of Marine Sciences University of Maine Orono, Maine, United States

Kevin Heasman Aquaculture Cawthron Institute Glenduan, New Zealand Roque Alberto Hours CINDEFI–​Centro de Investigación y Desarrollo en Fermentaciones Industriales Universidad Nacional de La Plata Buenos Aires, Argentina Juan Pablo Huchin-​Mian Departamento de Biología División de Ciencias Naturales y Exactas Universidad de Guanajuato Guanajuato, México Anes Dwi Jayanti Department of Fisheries, Faculty of Agriculture Gadjah Mada University Yogjakarta, Indonesia Andrew Jeffs Institute of Marine Science and School of Biological Science The University of Auckland Private Bag, AKL, New Zealand Per Meyer Jepsen Department of Science and Environment Roskilde University Roskilde, Denmark Lauren N. Jescovitch Michigan Sea Grant and MSU Extension Michigan State University Hancock, MI, United States of America Suadi Department of Fisheries, Faculty of Agriculture Gadjah Mada University Yogjakarta, Indonesia So Kawaguchi Australian Antarctic Division Channel Highway Kingston, TAS, Australia

Contributors Gordon H. Kruse College of Fisheries and Ocean Sciences University of Alaska Fairbanks Juneau, AK, United States of America Adrian J. Linnane South Australian Research and Development Institute (Aquatic Sciences) Adelaide, SA, Australia Boris A. López Departamento de Acuicultura y Recursos Agroalimentarios Universidad de Los Lagos Osorno, Chile Gustavo Lovrich Centro Austral de Investigaciones Científicas (CADIC-​CONICET) Ushuaia, Argentina Melissa B. Martin Institute of Marine and Antarctic Studies University of Tasmania Hobart, TAS, Australia W. Ray McClain H. Rouse Caffey Rice Research Station Louisiana State University Agricultural Center Rayne, LA, United States of America Luis M. Mejía-​Ortiz Departamento de Ciencias y Humanidades Universidad de Quintana Roo Chetumal, México Thomas J. Miller Chesapeake Biological Laboratory University of Maryland Center for Environmental Science Solomons, MD, United States of America Carlos Navarro-​Barranco Departamento de Zoología Universidad Autónoma de Madrid Ciudad Universitaria de Cantoblanco Madrid, Spain

Stephen Nicol IMAS Hobart Waterfront, Hobart CBD Campuses University of Tasmania Hobart, TAS, Australia Barbara F. Nowak Institute of Marine and Antarctic Studies University of Tasmania Hobart, TAS, Australia Miguel A. Penna-​Díaz Facultad Ciencias del Mar Universidad Católica del Norte Coquimbo, Chile Adam Powell Department of Biological and Environmental Sciences Kristineberg University of Gothenburg Fiskebäckskil, Sweden Macarena Ros Departamento de Biología Facultad de Ciencias del Mar y Ambientales Universidad de Cádiz Campus de Puerto Real Puerto Real, Cádiz, Spain Taku Sato Research Center for Marine Invertebrates Research Institute of Fisheries and Environment of Inland Sea Japan Fisheries Research and Education Agency Hiroshima, Japan Jeffrey D. Shields Environmental and Aquatic Animal Health Virginia Institute of Marine Science Gloucester Point, VA, United States of America Bradley G. Stevens University of Maryland Eastern Shore Princess Anne, MD, United States of America

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xiv Contributors Kristian Syberg Department of Science and Environment Roskilde University Roskilde, Denmark

Wagner C. Valenti Aquaculture Center (CAUNESP) UNESP - São Paulo State University, São Paulo, Brazil

Martin Thiel Facultad Ciencias del Mar Universidad Católica del Norte Coquimbo, Chile

Richard A. Wahle School of Marine Sciences and Lobster Institute University of Maine Darling Marine Center Walpole, ME, United States of America

José M. Tierno de Figueroa Departamento de Zoología Facultad de Ciencias Universidad de Granada Grenada, Spain

Reginald A. Watson Institute for Marine and Antarctic Studies University of Tasmania Hobart, TAS, Australia

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Landings (millions of tons)

5 4 3 2 1 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Shrimp

Crab

Krill

Lobster

Other Crustacean

Fig. 1.1. Global landings of crustaceans from wild fishery harvests by taxa group, 1950–​2014 (Watson 2017). The increase in landings in the category “other crustaceans” from 2002 is partially driven by landings of mantis shrimp, barnacles, and squat lobsters but more substantially by broader coverage of data from minor producing countries where catch was simply reported as “crustacean”.

(A) Shrimp

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Tons (avg 2005–2014) 5×102

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Fig. 1.2. Landings of crustaceans from wild fishery harvests by country, averaged from 2005 to 2014 (Watson 2017). Note that this illustrates the country reporting the catch, not necessarily the location of the catch.

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Fig. 1.5. Male (left) and female (right) ornate rock lobsters Panulirus ornatus are easily distinguished by the pleopods beneath their abdomen, which has enabled the development of different regulations for each sex, such as shorter female fishing seasons as part of protection of egg production.

Fig. 1.6. Several different countries harvest northern shrimp Pandalus borealis in the north Atlantic. Harvesting of shared stocks like this is common to many crustacean fisheries and ideally involves collaboration in data collection, assessment, and sharing arrangements, such as occurs in this case through the Northwest Atlantic Fisheries Organization (source: Canadian Government Fisheries Department).

Fig. 1.7. Supply chains for seafood in Asia such as these blue swimmer crabs landed at a fishing village in Java, Indonesia, are changing in response to greater wealth and reliability of transport routes.

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Fig. 3.1. Representative and commercially important species of the three lobster families. Clawed lobsters (Nephropidae) A. Homarus americanus and B. Nephrops norvegicus. Spiny lobsters (Palinuridae) C. Panulirus argus and D. Jasus edwardsii. Slipper lobsters (Scyllaridae) E. Thenus orientalis and F. Scyllarides latus. Figure 3.1C, photo courtesy of Robert Fenner. Figure 3.1D with permission from © OceanwideImages.com; Fig. 3.1E, photo courtesy of Anders Salesjö; Fig. 3.1F, photo courtesy of Peter Koelbl; Figs. 3.1D, 3.1E, and 3.1F with permission from their respective authors.

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Fig. 4.5. Shrimp fishery gear and catch. (A) Northern white shrimp, Litopenaeus setiferus. (B) Macrobrachium nipponense, target of one of two important freshwater caridean shrimp fisheries (China). (C) Gulf of Mexico double-​rigged shrimp trawler, with twin otter trawls and try net. (D) Skimmer net trawler with twin skimmer nets and single stern otter trawl. (E) Skimmer net being lowered into the water; the sled is at the bottom of the net frame and skims over the bottom with the net bag trailing behind the net frame. (F) Trawl catch in the sorting box with fish bycatch (discards in the Gulf of Mexico). (G) Baskets of sorted penaeid shrimp catch, principally Litopenaeus setiferus (Gulf of Mexico), after bycatch is removed. nb, net bag; nf, net frame of skimmer net (arrow points to top horizontal bar); ob, otter trawl boards; or, outrigger; s, sled of skimmer net; tn, try net; v, vertical bar of skimmer net. Scale bars in A and B represent 2.5 cm. Figs. (A), (C–G) courtesy of Louisiana Sea Grant Program; (B) courtesy of Martin Thiel.

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Fig. 6.1. (A) Antarctic krill. (B) Antarctic krill fishing vessel Saga Sea operating in the Southern Ocean. (A) Photo courtesy of Rob King; (B) photo courtesy of Aker BioMarine.

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Fig. 7.1. Edible barnacles. (A)  Gastronomic dish of stalked barnacles (Pollicipes pollicipes). (B)  Giant acorn barnacle (Austromegabalanus psittacus) attached to the substratum showing cirral activity. (C)  Extraction of giant barnacles by artisanal fishers in Carelmapu, southern Chile. Specimens of A. psittacus without calcareous wall plates, showing (D) adductor muscles (white arrows) and (E) the female gonad (black arrow).

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Fig. 7.2. Individual and sale boxes of “mine fujit subo” (Balanus rostratus) in Aomori market, northern Japan.

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Fig. 7.3. Barnacle culture in suspended systems. (A) Tubular systems for growth of giant barnacles, Austromegabalanus psittacus, “picoroco,” in northern Chile (30°S). (B) Hummock (aggregate) of cultured A. pittacus individuals after 18 months. (C) Juvenile specimens of A. psittacus settled onto artificial collectors.

Fig. 7.4. Megabalanus azoricus (“craca”) specimens adhered to an artificial tubular collector at a depth of 10 m. Photograph courtesy of Christopher Pham.

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Fig. 7.5. Stomatopod fisheries. (A)  Stomatopod sales (spot-​tail mantis shrimps, Squilla mantis) in a Spanish market. (B) Live Japanese mantis shrimps (Oratosquilla oratoria) in a market in Thailand. (C) Stomatopods on sale in a Taiwanese market. Photographs A and B from Wikimedia Commons (CC Ø), and Photograph C courtesy of Martin Thiel.

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Fig. 7.6. Sandhopper fishery in sandy beaches in the central coast of Chile (34°S). (A) The sandhopper Orchestoidea tuberculata; (B) deployment of traps; (C) plastic bag trap; (D) plastic bottle trap; (E) gathering of the extraction; (F) boiling; and (G) sun drying. Photograph A courtesy of Jorge Pérez Schultheiss. Photographs B–​G from Tapia-​Lewin et al. (2017) with permission © Springer; high-​resolution files courtesy of Karina Vergara.

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Fig. 8.2. The giant river prawn Macrobrachium rosenbergii. (A)  M.  rosenbergii adult male specimen. (B)  Harvested M. rosenbergii individuals from a culture. Figures are courtesy of Wikimedia Commons (under CC Creative Commons license).

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Fig. 8.3. The Andes river prawn Cryphiops caementarius. (A) Male “garrudo” morphotype with one oversize chelae to defend their territory in agonistic encounters. (B) Male adult individual hidden in their refuge. Figure 8.3A photo courtesy of Arthur Anker with permission and Figure 8.3B photo courtesy of Ivan Hinojosa with permission.

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Fig. 8.6. Crayfishes. (A) Louisiana red swamp crayfish Procambarus clarkii and (B) signal crayfish Pacifastacus leniusculus. Figures are courtesy of Wikimedia Commons (under CC Creative Commons license).

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Fig. 9.1. Macrobrachium rosenbergii after harvest. Note the ovigerous females with eggs attached to the pleopods and dominant males with large blue claws.

Fig. 9.4. Hatchery tanks in a large hatchery in Thailand, which operate in a flow-​through system.

Fig. 9.5. Recirculating hatchery system in Aquaculture Center, São Paulo State University (UNESP), Brazil. Note the biofilter on the left.

Fig. 9.6. Earthen grow-​out ponds. Camarão de Prata, a farm with 5 ha in Brazil.

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Fig. 10.4. (A) Large shrimp farm in Sumatra, Indonesia, and (B) a medium-​size shrimp farm in the United States.

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Fig. 10.5. Images from shrimp farms:  (A) Feeding shrimp; (B)  a small Asian paddlewheel aerator; (C)  a large Asian paddlewheel aerator; (D)  highly efficient paddlewheel aerator based on Auburn University design recommendations; (E) propeller-​aspirator-​pump aerators in shrimp ponds; (F) water gate of shrimp farm.

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Fig. 11.5. (A) Procambarus clarkii pond on Chongming Island in the mouth of the Yangtze river in China. (B) Note the hoop net, which is one variation of gear used in China for capturing crayfish. Photographs by Martin Thiel

Fig. 11.6. Commercial redclaw crayfish (Cherax quadricarinatus) farm in Queensland province of Australia.

Fig. 11.7. Marron (Cherax cainii) grow-​out systems in Southwestern Australia are typically small earthen ponds equipped with supplemental aeration and bird netting. Note the nests of netting material suspended within the water column to serve as vertical substrate and “hides” for juvenile crayfish.

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Fig. 11.9. Current standard square-​mesh, three-​funnel pyramid trap used in the shallow-​water crayfish ponds of the southern USA as viewed from the outside (left photo) and from the open top looking down (right photo). The open top allows for rapid emptying of the catch and rebaiting, while the collar minimizes escape. Traps are emptied and rebaited from boats without stopping at each trap.

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Fig. 12.3. Examples of compartmentalized systems used for culturing of Homarus species. (A) Sea-​based cluster secured on the seabed, providing compartments for two lobsters per spur (Knudsen and Tveite 1999). (B) Sea-​based plastic containers housing individual lobsters inside mesh basket system placed on the seabed (Beal 2009). (C)  Sea-​based, custom-​made single containers suspended from a mussel raft (Perez-​Benevente et  al. 2010). (D)–​(F) Sea-​based oyster basket containers suspended from mussel rafts and long lines (Perez-​Benevente et al. 2010, Daniels et al. 2015). (G) Land-​based rotary system housing 28 lobsters (Kristiansen et al. 2004). (H) Sea-​ based compartmentalized patented container (Lobster Grower, 2018). (I)  Land-​based compartmentalized patented system (Drengstig and Bergheim, 2013).

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Fig. 13.1. (A) Indo-​Pacific cleaner shrimp Lysmata amboinensis, the most popular marine ornamental decapod in the aquarium trade. (B) Monaco cleaner shrimp Lysmata seticaudata. (C) Coral banded boxing shrimp Stenopus hispidus. (D) Hinge beak shrimp Cinetorhynchus. (E) Harlequin shrimp Hymenocera elegans. (F) Dwarf reef lobster Enoplometopus. (G) Sexy shrimp Thor amboinensis. (H) Blue-​legged hermit Clibanarius tricolor. (I) Emerald crab Mithraculus sculptus. ( J) Sally Lightfoot Percnon gibbesi. (K) Clown crab Platypodiella spectabilis. (L) Arrow crab Stenorhynchus seticornis.

Fig. 13.6. Adult specimens of the sympatric eastern Atlantic species Lysmata seticaudata (lower left) and Lysmata uncicornis (up and right) exhibiting their daytime coloration. All specimens are already simultaneous hermaphrodites, with the two specimens on the left side of the image brooding embryos on their abdomen and exhibiting well-​developed ovaries on the dorsal region of their carapace (a sign that larval hatching will soon take place) (scale bar 10 mm).

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Fig. 15.1. Examples of pathogens that damage commercially important aquaculture or fisheries species. (A) White spots in the epidermal cells of the carapace indicative of white spot syndrome virus (WSSV) in Penaeus monodon. (B) Histological section of the epidermal cells of an infected shrimp. Cowdry-​A type inclusions (arrowheads) are indicated. (C) Transmission electron micrograph of WSSV virions showing the characteristic tail (arrows). (D)  Early benthic juvenile of an American blue crab, Callinectes sapidus, a typical instar for infection by Hematodinium perezi. (E) Filamentous trophont (white arrow) and a cluster colony forming ameboid trophonts (black arrow). Neutral red stain. (F) In vitro culture of an arachnoid trophont of H. perezi. (G) Panulirus argus, the host for Panulirus argus Virus 1. (H) Spongy connective tissue cells of the hepatopancreas exhibiting Cowdy-​ A type inclusions and hypertrophied nuclei. (I) Transmission electron micrograph of PaV1 virions (arrows show the virions) from lobster hemolymph. ( J) Mature Homarus americanus with a severe case of epizootic shell disease (ESD). Note the loss of the rostrum, right antenna, and both antennules and damage to the carapace, left chela, limbs, and abdominal somites. (K) Histological section of the carapace of a lobster with ESD with loss of several layers of the cuticle, melanization (arrowhead), pseudomembrane formation P, and intensive hemocyte infiltration H. Figure (A) is from Escobedo-​Bonilla et al. (2008), with permission. Figure (C) is from Durand et al. (1996), with permission. Figure (I) is modified from Shields and Behringer (2004), with permission.

Fig. 17.4. Marinas are important entry points for invasive species of amphipods. Caprella scaura (see detail in the floating pontoon of Puerto America, Cádiz) is an alien species that has widely spread along the Mediterranean during the last decades. Map showing the distribution of the different subspecies of C. scaura. C. scaura typica and C. scaura scaura (considered as the same subspecies) is the only form that is expanding its distribution range (data from Ros et al. 2014; see text of Ros et al. 2014 for details of the figure). Photo courtesy of José M. Guerra-​García.

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(A)

(B)

(C)

(D)

(E)

(F)

(G)

(H)

Fig. 19.7. Examples of decapod (edible crab, C. pagurus), supply chain technologies aimed to maintain cost-​effective and physiologically appropriate conditions. (A) Crabs caught using static gear are collected in “bins” on deck and unloaded and weighed adjacent to goods vehicles for onward road transport. (B) Detail of conventional vivier tanks. Note high stocking density and unbanded claws. (C) Alternative douche system using intermittent water showers. (D) Alternative misting system maintains a humid atmosphere (water is not reused to maintain water quality). (E) Dry transport in damp and cooled insulated boxes. (F) Weighing of live edible crab after 48-​h international transport in lorry tanks from England (Weymouth) to Portugal (Setúbal). (G), (H) Grading and maintenance in a holding and dispatch center (Setúbal). The system is a semi-​recirculating aquaculture system (RAS) incorporating basic filtration (protein skimming). A, B, F, H, photos by Sara Barrento; C, D, E, from Smyth and Uglow (2015), courtesy of the ACRUNET project, John Fagan, Roger Uglow, and Katie Smyth.

1 CRUSTACEANS AS FISHERIES RESOURCES: GENERAL OVERVIEW

Caleb Gardner, Reginald A. Watson, Anes Dwi Jayanti, Suadi, Mohsen AlHusaini, and Gordon H. Kruse

Abstract Much of the biological and other research efforts on crustaceans have been driven by their importance to humans as a food source. Production comes from a diverse array of methods and scales of extraction, from small recreational or subsistence fisheries to industrial-​scale operations. Most crustacean catch comes from shrimp fisheries, with over two million tons taken in 2014, mainly by trawl. The genera Acetes, Fenneropenaeus, and Pandalus account for around three quarters of this catch. Crab, krill, and lobster are the other main crustacean products (around 600,000 t crab, 380,000 t krill, and 300,000 t lobster in 2014). Trends in crustacean fisheries are broadly similar to those of other seafood, although crustaceans often target different market segments and receive higher prices than fish. Crustacean fisheries management faces many challenges with management of bycatch from trawl gears especially significant. Fortunately, crustaceans tend to be easily handled with low discard mortality, and this has enabled widespread use of regulations based on size, maturity, or sex (e.g., male-​only fisheries). Total allowable catch (TAC) limits are widely used and highly effective for ensuring sustainable harvests when set responsibly using good information. TAC systems are often combined with catch share or individual transferable quota systems, which had a mixed history in crustaceans, sometimes reducing overall community benefit. This parallels the challenge facing fisheries globally of ensuring that harvests are not only sustainable but also deliver benefits to the wider community beyond the commercial fishers; management of some crustacean fisheries is at the forefront of these developments.

Caleb Gardner, Reginald A. Watson, Anes Dwi Jayanti, Suadi, Mohsen AlHusaini, and Gordon H. Kruse, Crustaceans as Fisheries Resource In: Fisheries and Aquaculture. Edited by: Gustavo Lovrich and Martin Thiel, Oxford University Press (2020). © Oxford University Press. DOI: 10.1093/oso/9780190865627.003.0001

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TRENDS IN GLOBAL CRUSTACEAN LANDINGS FROM WILD HARVEST FISHERIES Crustacean fisheries are highly diverse in terms of taxa, markets, gear type, and global distribution. Production is dominated by marine and estuarine species, although significant freshwater production also occurs, especially in Asia. Crustaceans comprise only around 5% of the global total fisheries production, which was around 100 million tons in 2014, including illegal, unreported, and unregulated (IUU) fisheries (Watson 2017). Total production has steadily increased to a record high total catch in the most recent year with full data, 2014 (Fig. 1.1). Global trends in crustacean wild fisheries were examined using recent data from a range of public sources compiled by Watson (2017) for global catch. These data include commercial landings in addition to estimates of small-​scale, illegal, and unreported landings. Data were filtered to remove product that was reported as wild catch but appeared to be from aquaculture. There were two significant taxonomic groups affected by this process. One was Chinese landings of crustaceans categorized simply as “miscellaneous marine crustaceans,” which rose rapidly to peak in 2002 with no further records. Similarly, Chinese landings of the “gazami” crab Portunus trituberculatus increased rapidly over the last decade. This production appears to be mainly from aquaculture rather than wild fisheries as this crab has become one of the most important aquaculture crustacean species in China, especially in the Zhejiang and Jiangsu Provinces adjacent to Shanghai (Jin et al. 2013). The majority of crustacean catch are shrimp, which is dominated by a few genera (Table 1.1). Pelagic Acetes spp. are the most important species by catch. They are harvested in Asian seas and mainly sold after processing into shrimp paste. Large volumes of euphausiids or krill are also mainly marketed in highly processed forms. Other high-​volume shrimp genera are Fenneropenaeus, Pandalus, Penaeus, Metapenaeus, Farfantepenaeus, Pleoticus, and Litopenaeus, most of which are sold as higher value, whole-​product forms. Higher value production of crab and lobsters is dominated by the genera Chionoecetes and Homarus, respectively, both of which are taken in northern, temperate waters. In terms of landings, 6

Landings (millions of tons)

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5 4 3 2 1 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Shrimp

Crab

Krill

Lobster

Other Crustacean

Fig. 1.1. Global landings of crustaceans from wild fishery harvests by taxa group, 1950–​2014 (Watson 2017). The increase in landings in the category “other crustaceans” from 2002 is partially driven by landings of mantis shrimp, barnacles, and squat lobsters but more substantially by broader coverage of data from minor producing countries where catch was simply reported as “crustacean”. See a color version of this figure in the centerfold.

Table 1.1.  Landings of important genera for crustacean wild fisheries in 2014. Genera were generally only included where total catch exceeded 1,000 t. Values presented here will understate total catch in fisheries where the taxonomy of catch was not reported to level where genus could be determined (Watson 2017). Shrimp Acetes (Akiami paste shrimp) Fenneropenaeus (banana shrimp) Pandalus (northern, Aesop, humpback shrimp) Pleoticus (Argentine red, royal red shrimp) Metapenaeus (endeavour, shiba, speckled shrimp) Farfantepenaeus (brown, pink, red spot shrimp) Litopenaeus (white shrimp) Palaemon (common prawn) Crangon (common shrimp) elicertus (king, caramote prawn) Aristeus (striped red shrimp) Heterocarpus (nylon shrimp) Artemesia (stiletto shrimp) Haliporoides (knife shrimp) Marsupenaeus (karuma prawn) Nematopalaemon (whitebelly prawn) Other Crustacean Cervimunida, Munida (squat lobsters) Megabalanus (giant barnacle) and other barnacles

tons (1,000s) 750 418 408 199 163 142 90 58 49 16 14 7 5 5 3 1 4 0.4

Crab Chionoecetes (tanner, snow crab) Charybdis (Indo-​Pacific swimming crabs) Cancer (edible, Dungeness, rock crab) Callinectes (blue crab) Lithodes and Paralithodes (king crab) Geryon, Chaceon (deep sea crab) Maja (spider crab) Carcinus (green, shore crab) Necora (velvet crab) Menippe (stone crab) Lobster Homarus (American, European, clawed lobster) Nephrops (Norway lobster) Jasus (red, spiny, rock lobster) Panulirus (rock, spiny lobster) Palinuris (rock, spiny lobster) Metanephrops (scampi) Ibacus (sand crayfish, bug) Krill Euphausia (krill)

tons (1,000s) 251 113 107 72 41 9 7 3 3 1 208 62 27 7 5 2 1 386

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Fisheries and Aquaculture major crab fisheries also include those for Portunus, Callinectes, Charybdis, and Cancer. There is a diversity of low-​volume taxa included in the category of “other crustaceans,” including squat lobsters, mantis shrimp, and barnacles (see Chapter 2, in this volume). Shrimp fisheries use a range of fishing gears, although most of the catch is taken by bottom trawls, which accounted for around 60% of the global crustacean catch across all taxa in 2014. Artisanal fisheries for shrimp and other crustaceans involve a wide range of nets that accounted for around 20% of catch in 2014, including stake nets, cast nets, fyke nets, trammel nets, and gillnets, all of which are sometimes used within a single fishery, such as the inshore shrimp fishery off western Sri Lanka (Croos and Pálsson 2013). Twelve percent of the global crustacean catch was taken with traps in 2014, mainly consisting of crabs and lobsters, although traps are also used in other crustacean fisheries, such as the northern shrimp Pandalus borealis in the northwest Atlantic (Moffett et al. 2012) and other species of pandalid shrimp in the northeast Pacific (Kruse et al. 2000). Midwater trawls are used in krill fisheries and have been extensively refined over the last few decades for efficiency of fuel use and selectivity (Korzun and Zhuk 2015, Xu et al. 2015). Only a negligible proportion of the total global crustacean catch is taken with gears other than trawls, nets, and traps. Of these, hand collection or diving for tropical lobster species is the most significant economically and socially, in particular for Panulirus argus, which is taken in numerous countries throughout the Caribbean (Cabrera and Defeo 2001). Diving for this highly desirable species involves a special concern because of the high social cost of barotrauma in some fishing communities (López-​Tristani et al. 2004). Crustacean harvesting is not evenly distributed globally, with a few countries dominating harvests. China leads global harvests for all main categories of crustacean types except for lobsters, which are harvested mainly in North America and Oceania (Fig. 1.2). The African (A) Shrimp

(B) Lobster

(C) Crab

(D) Krill

(E) Other

Tons (avg 2005–2014) 5×102

50 0

102

5×103

15×102

104

105

106 5×105 >106

Fig. 1.2. Landings of crustaceans from wild fishery harvests by country, averaged from 2005 to 2014 (Watson 2017). Note that this illustrates the country reporting the catch, not necessarily the location of the catch. See a color version of this figure in the centerfold.



Crustaceans as Fisheries Resources

continent has lower crustacean landings relative to most other regions, although this will be partially an artefact of catches taken off Africa but reported by European and Asian countries.

CRUSTACEAN FISHERIES MARKETS Price Signals Market trends of commercially harvested crustaceans have varied substantially across different taxa over the last decade, which has been attributed to a range of factors, including a change in the supply due to aquaculture substitutes, a change in the macroeconomics of major markets (especially China), a change in the supply due to wild harvests, and market dynamics around product categories (Huang 2015). Rock lobsters are an especially highly valued taxon, with an average price of USD37.60 per kg in 2016 and a 56% increase in the nominal price over the decade (Fig. 1.3; UN Comtrade 2016). The price of crabs has also increased across this period, although to a smaller extent. For example, average prices paid for crabs in the eastern Bering Sea (United States) increased for a number of crab species, with the largest increase of 26% from USD8.44 to USD10.67 for red king crab (Paralithodes camtschaticus) over just 2012–​2016 (Garber-​Yonts and Lee 2017). There is little or no aquaculture production for these taxa, and producers have benefited from increasing affluence and improvements to the supply chain into China (Norman-​Lopez et al. 2014). The price has been further increased by regulated limits on the total catch of most major suppliers. Other crustacean taxa have had more stable prices over the last decade, although the reason for this varies (Fig. 1.3). Clawed lobsters (Homarus spp.) have had a stable price of around USD15.00 per kg from 2006, with rising production from the northeast North America limiting the price

40 35 30 USD kg−1

25 20 15 10 5 0

2001

2006

2011

2016

Rock lobster Crab Shrimp Clawed lobster

Fig. 1.3. Market price of broad categories of crustacean products 2001–​2016 (UN Comtrade 2016).

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Fisheries and Aquaculture growth (Pereira and Josupeit 2017). Shrimp have also had stable prices over the last decade, but over the past three decades through to October 2015, the price of shrimp has actually fallen by 27.5% due to the rising global supply from aquaculture. Crustacean prices typically vary from year to year in response to changes in the supply and demand, such as the plummet in shrimp prices in 2015 due to change in both production and demand in the United States, the European Union, and Japan (FAO 2016). Evolution of Products and Markets Crustacean product forms and markets have evolved as new supply chains have developed and market preferences have shifted. Lobsters, crabs, and shrimp are increasingly being sold live into higher priced markets because of more efficient supply chains, especially due to the reduction in airfreight times resulting from improvements in logistics (Philp et al. 2015). Markets are also influenced by changes in trade regulations, such as licenses or quotas required for imports, subsidies, and exclusion of certain species or products for biosecurity. Changes to these barriers have recently affected exports of African crustaceans traded into European markets (Mapfumo 2013). Human consumption markets for crustaceans now need to take into account factors that were not considered 20 years ago. These include consideration of welfare or humane killing on processing and holding of crustaceans (Buckhaven et al. 2012; see Chapter 19 in this volume), sustainability reporting and third-​party certification (Bellchambers et al. 2016), regulation of acceptable levels of toxins such as from harmful algal blooms (Ryder et al. 2014), organic status, and local provenance (Fonner and Sylvia 2015). Crustacean fisheries contribute product forms beyond seafood for human consumption, such as krill oil products, chitin, and carotenoid pigments (Ulven et al. 2010, Bahasan et al. 2017). Chitin, in particular, has an extraordinarily wide range of uses, such as adjuvants for vaccination and drug delivery, textiles, cosmetics, and paper (Muzzarelli 2010, Younes and Rinaudo 2015; see Chapter 18 in this volume).

MANAGEMENT As with most natural resources, management of crustacean fishery harvests is important to prevent stocks from becoming depleted, which in turn reduces productivity and associated benefits, including food, employment, and profit. At the most basic level, management can involve setting simple passive regulations, such as minimum legal size limits or areas closed to fishing. Management systems for some of the more valuable and data-​rich crustacean fisheries have undergone substantial changes over the last few decades as part of a wider transformation of fisheries management toward more formal harvest strategies driven by conservation concerns and advancements in quantitative stock assessment capabilities. These were originally a general collection of regulations designed to produce good management outcomes (Zheng et al. 1997) but have evolved into a series of very specific elements. These elements are defined objectives, which then lead to the selection of performance indicators and reference points and control rules that alter harvests so that the stock is managed away from limit reference points and toward target reference points (Fogarty and Gendron 2004, Dowling et al. 2015). Harvest strategies typically need to consider uncertainty in the estimation of parameters, which leads to more conservative reference points and control rules.



Crustaceans as Fisheries Resources

Governance Decision-​making in crustacean fisheries involves the full spectrum from highly regulated fisheries where decisions are fully in the hands of the government (often termed command-and-con­trol), to co-​ management where government and stakeholders share governance responsibilities, to situations where control is divested to harvesters (termed self-​management; Sumaila and Dominguez-​Torreiro  2010). Southern Ocean krill fisheries are an example of a highly regulated crustacean fishery where catch limits are set by government with limited influence of industry. The command-​and-​control type governance system in these krill fisheries arose in part because of the small number of large operators and the need for intergovernment negotiations to manage harvesting from international waters (Croxall and Nicol 2004). A more complex command-​and-​control type governance system has been established for the management of crab fisheries in the eastern Bering Sea, which involves federal regulation by the North Pacific Fishery Management Council and state regulation by the Alaska Board of Fisheries (NPFMC 2011). In this instance, there is considerable input by industry and other fishery stakeholders in public meetings of both state and federal management bodies. Even greater input of “stakeholders” occurred in management of noncommercial harvests of lobsters and other species in Maunalua Bay, Hawai’i, for example, resulting in the divestment of government authority (Kittinger 2013). Co-​management arrangements similar to this are common, especially with small-​scale crustacean fisheries, although stakeholder involvement is often limited to those who harvest rather than the broader public owners of the resource. The input of the fishing industry in management decisions can be especially helpful in tailoring harvesting to market demand and product quality. This is taken to the extreme in some trawl fisheries such as the Spencer Gulf shrimp fishery in southern Australia, which uses real-​time collection and analysis of data from the fleet to rapidly adjust harvesting in response to market traits (Carrick and Ostendorf 2007). Seminal examples of fishery governance and management often come from crustacean fisheries, perhaps because their high value promotes creative solutions to management. These include the spatial allocation of fishing grounds to individual operators or collectives in Maine, USA, and the Juan Fernandez Islands, Chile (Steneck et al. 2017), and developments in the regulation of shrimp trawling, such as improvements in selectivity and landing obligations (Bellido et al. 2011). The rise of third-​party certification has involved formal evaluation of the effectiveness of governance and management with crustacean fisheries at the forefront, with the Australian western rock lobster Panulirus cygnus fishery being the first fishery to receive Marine Stewardship Council (MSC) certification. Interestingly, crustacean fisheries have problems with governance and management criteria at a higher rate than fisheries of other taxa undergoing MSC assessment (Bellchambers et al. 2016). Management Objectives Fish stocks are traditionally viewed as common property of the jurisdiction, managed by the government to the benefit of the community. In most jurisdictions, the objectives of management are defined in legislation or fishery management plans, such as in this example from the European Union (Article 2 of Council Regulation [EC] 3760/​92):  “to protect and conserve available and accessible living marine aquatic resources, and to provide for rational exploitation on a sustainable basis, in appropriate economic and social conditions for the sector, taking into account of its implications for the marine ecosystem, and in particular taking into account of the needs of both producers and consumers.” This example is a typical objective for crustacean fisheries in that it recognizes the need to balance the benefits to the community from harvests with acceptable levels of ecosystem impacts

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Fisheries and Aquaculture and the long-​term productivity of the resource. Management objectives for the target species often have two elements, which are those associated with sustainability and those associated with trying to increase the benefit obtained from harvests (Mardle et al. 2002). Sustainability objectives protect the reproductive output of the stock and so are based on measures of egg production or a proxy for egg production, including spawning stock biomass or catch rates. Management attempts to maintain sustainability of the stock by keeping egg production (or its proxy) above a minimum acceptable level or limit reference point, such as 20% of estimated unfished biomass, as applied to most of the crustacean fisheries in the eight Australian fishing jurisdictions (Flood et al. 2016). The importance of maintaining the reproductive output of crustacean stocks as part of fishery management is the motivation for the extensive research effort on crustacean reproductive biology. In practice, management objectives directed to the benefits of crustacean fishery harvests generally target either maximum sustainable yield (tonnage; MSY) or maximum economic yield (profit; MEY) or their proxies. Either choice involves higher levels of stock than is required to meet egg production limits required for sustainability, which means that managing for MEY or MSY is more conservative and challenging than just achieving sustainability (Kompas et al. 2010). MSY is preferred in fisheries, such as the blue crab fishery in the Chesapeake Bay, USA (Huang et al. 2015), or the shrimp fisheries of Nigeria ( Jimoh et al. 2010), where the fishery benefits the community through employment and the supply of food. MSY is also targeted in some fisheries where there is not a direct local consumption benefit, such as the Norway lobster Nephrops norvegicus in the northeast Atlantic, where target product is mainly exported from the region. This is because a strategy of targeting MSY leads to higher catch and effort so there is more direct employment from the fishery (Vasilakopoulos and Maravelias 2016). In many other crustacean fisheries, regulations keep the catch below the MSY and instead target the MEY. This is done to maintain high stock levels and high catch rates and reduce the marginal cost of harvesting, including reducing the costs associated with employment inputs (Caputi et al. 2015). This approach occurs where management prioritizes economic yield rather than food supply or employment, which is more appropriate for countries with high food security and diverse employment opportunities. Most Australian lobster fisheries are managed to reduce the catch well below the MSY using tradeable quota systems to create positive economic yield; these are variants of systems also known as catch shares, individual fishing quotas (IFQs), or individual transferable quotas (ITQs) (Caputi et al. 2015, Gardner et al. 2015a). The economic yield from MEY fisheries flows to either the community or private firms depending on the governance system. In these examples of Australian lobster fisheries, the economic yield flows entirely to the private owners of the quota assets. The economic yield is revealed as rent paid by lease fishers to the owners of the quota shares, and this rent can be more than 70% of the total gross value or revenue (van Putten and Gardner 2010, Emery et al. 2014). In an interesting, albeit somewhat complicated, twist on such quota systems, the crab rationalization program for crab fisheries in the Bering Sea and Aleutian Islands (USA) operates as a “two-​pie” system in which harvesters hold quota shares used to calculate their annual IFQ and processors hold quota shares (PQS) used to calculate their individual processing quotas (Fina 2005). In an attempt to preserve historical community employment, processors can only buy crabs landed under authority of an IFQ and vice versa. The program also limits the amount of PQSs that can be used outside of communities with historical reliance on crab fisheries and also allows these communities to purchase quota shares and lease them to community residents. Reducing the food production and employment rate to create private rent may benefit the community if the quota owner reinvests or spends the rent within the community. In practice, however, there are many reasons why this often does not occur, such as where ownership of catch shares (and thus rents) is transferred out of the region or country (Pinkerton and Edwards 2009). In a few rare cases, systems are used to ensure a share of the rent generated from MEY fisheries is collected to



Crustaceans as Fisheries Resources

the benefit of the public or community. These include auctioning out harvest rights in the Chilean squat lobster fishery (Cerda-​Amico and Urbina-​Veliz 2001) or royalty payments for access (Haynie 2014). These processes are surprisingly rare in fisheries given that community benefit is an objective of most fisheries legislation and is a routine consideration with other industries that use scarce public resources such as forestry or mining (Amalu et al. 2016). Controlling Harvests Controlling the harvests of crustaceans to meet management objectives is similar to that of other fisheries except for two ways. The first is that size limits are unusually widespread in crustacean commercial fisheries because of the high individual unit price and low discard mortality (Ogawa et  al. 2011; Fig. 1.4). Second, it is often possible to have sex-​based regulations because of the ability to easily differentiate the sex and maturity of crustaceans. For example, harvesting of ovigerous females is prohibited in the lobster fishery in Sweden and Norway (Sundelöf et al. 2015), different closed seasons and size limits are used for female lobsters in the Southern Australia fishery (Gardner et al. 2015b; Fig. 1.5), and v-​notching of the telson is used to reduce the exploitation rate of females in the Irish lobster fishery (Tully 2001). The ability to differentiate the sex of crustaceans is used to prohibit the harvesting of females in many crustacean fisheries, a management approach that is unusual in fisheries for other animals (Bunnell et al. 2010). Rates of egg carrying and the size of the clutch in female crabs and lobsters is used to determine the spatial and temporal variability of reproductive output and health of a population (Orensanz et al. 1998). For example, harvests of red king crab in Russian trawl and pot-​based fisheries have been restricted to males (Dvoretsky and Dvoretsky 2017); likewise, female harvests are prohibited in pot fisheries for all crab species in Alaska (Kruse 1993). Many crustacean seafood products have large seasonal changes in price, driven by changes in both demand (e.g., around festivals) or biological patterns in supply (e.g., seasonal molting events). The management of the harvesting of crustaceans is increasingly taking account of opportunities to receive higher prices, a process termed fishing to market. One approach to fishing to market that is unique to crustaceans is targeted harvesting of animals that are about to molt; the animals can then be held in tanks, collected immediately after molting, and sold at a premium price as “soft shelled” (Diogo et al. 2017). Along the eastern coast of the USA and the Gulf of Mexico, peeler crabs (about to molt) and soft-​shell blue crabs (Callinectes sapidus) are marketed separately from hard-​shell crabs and obtain higher prices (Bunnell et al. 2010). The size at harvest can also be managed, such as in the lobster fishery off Gisbourne, New Zealand, where the total revenue was increased despite a reduction in catch by adjusting size limits to target the more desirable smaller lobsters (Breen and Kendrick 1997). The system of allocating fixed shares of catch or areas of the seafloor to individual firms or fishers is intended to provide an incentive for fishers to adjust catch in response to market demand rather than compete for catch. This process has been successful in many fisheries, such as some of the small-​scale Caribbean lobster fisheries (Headley et al. 2017), although outcomes are mixed. In the Tasmanian lobster fishery, individual catch shares were transferable and leased between fishers so any one individual fisher did not have an effective limit on their annual catch. They also had an economic incentive to fish provided each trip was profitable in the short run. As a result, the fishery contracted to a small number of operators fishing throughout the year regardless of market demand (Emery et al. 2014). Fluctuation in stock productivity from year to year occurs in most fisheries because of changes in growth, survival, and recruitment. This temporal change is a significant challenge for controlling harvests of many crustacean fisheries especially in short-​lived species like shrimp, where annual fluctuation in biomass can vary by more than two-​fold. These situations risk high fishing effort on

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Fig. 1.4. Size limits are widely applied in crustacean fisheries, such as for king crab, because of low discard mortality plus the high value of individual animals, which make handling and grading worthwhile. Figure from Van Son and Thiel 2007, with permission from authors.

poor-​recruit year classes so the risk is ideally managed by adjusting harvests using recruitment data. For example, recruitment strength in shrimp stocks off Mozambique has been linked to the volume of river flows, a process common to many shrimp fisheries, which enables management to predict and respond to changes in recruitment (de Sousa et al. 2006). Many crustacean fisheries monitor

(A)

Crustaceans as Fisheries Resources (B)

Fig. 1.5. Male (left) and female (right) ornate rock lobsters Panulirus ornatus are easily distinguished by the pleopods beneath their abdomen, which has enabled the development of different regulations for each sex, such as shorter female fishing seasons as part of protection of egg production. See a color version of this figure in the centerfold.

recruitment and gain insight into future trends in the stock by monitoring the abundance of animals below the minimum legal size. This type of data has helped in examining long-​term declines in productivity in parts of the snow crab Chionoecetes opilio fishery in Canada (Mullowney et al. 2014) and is widely used in invertebrate fisheries off Western Australia (Caputi et al. 2014). An important, simple but underused process for reducing the risk of overfishing weak-​year classes is simply to ensure the stock levels are high, such as by keeping the catch below the long-​run MSY. This diminishes the need for recruitment monitoring and also provides stability of supply to markets (Caputi et al. 2015). Sharing the Catch An especially challenging issue in many fisheries, including crustacean fisheries, is the management of harvests where stocks are shared between different sectors, jurisdictions, or countries. This applies to most of the world’s largest crustacean fisheries, such as those for the Caribbean spiny lobster, krill, or Acetes shrimp. Failure to cooperate in management across national borders can be detrimental to the overall productivity of the stock, in particular when overharvesting of larval source areas reduces recruitment to other jurisdictions (Cochrane et al. 2004). To ensure conservation of crustacean and other fishery resources, a stock should be managed over its full range, including a full accounting of all fishing mortality. Formal management of shared stocks requires the creation of intergovernmental bodies for collaboration in science and management, such as the Northwest Atlantic Fisheries Organization, which deals with harvests of northern shrimp Pandalus borealis

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Fig. 1.6. Several different countries harvest northern shrimp Pandalus borealis in the north Atlantic. Harvesting of shared stocks like this is common to many crustacean fisheries and ideally involves collaboration in data collection, assessment, and sharing arrangements, such as occurs in this case through the Northwest Atlantic Fisheries Organization (source: Canadian Government Fisheries Department). See a color version of this figure in the centerfold.

(Fig. 1.6). A particularly interesting case is the shared management of the ornate lobster Panulirus ornatus because almost the entire stock transits during development from the nursery habitat in Australia to the spawning grounds in Papua New Guinea (Ye and Dennis 2009). Less successful outcomes for management of crustacean stocks that straddle political boundaries have occurred in the South China Sea, where there is no formal agreement to manage cumulative impacts, with the situation further complicated by political tensions in the region (George 2012). Crustacean resources benefit different and competing sectors, such as recreational or sport fishers, commercial fishers, subsistence fishers, traditional or cultural fishing, and non-​extractive users such as divers in marine parks. Rivalrous competition between these users means that catch-​ sharing systems can become political and difficult to resolve, as in the case of competing users of the Florida lobster resource, which include commercial, recreational, and charter fisheries (Harper 2015). Blurred boundaries between these sectors add an additional layer to resource-​sharing arrangements, such as the shift in commercial shrimp and lobster harvests in Palamós, Spain, to “pesca-​tourism” (Piasecki et  al. 2016)  or the shift from cultural to commercial harvesting by indigenous lobster fishers in the Torres Strait (Plagányi et al. 2018). It is difficult but not impossible to equate the value of fishery resources to commercial, recreational, and subsistence users given the divergent metrics required to each use of the resource. Thus, economic approaches to resource sharing generally involve trying to measure the marginal value or utility of the different sectors (not the expenditure or revenue) and reallocating catch so that these are balanced (e.g., Lee et al. 2014). Managing catch for non-​extractive users is a special case of resource sharing, although not a common issue in crustacean fisheries. A  modest non-​extractive economic value has been demonstrated from improved recreational experience when diving with lobsters versus dives



Crustaceans as Fisheries Resources

without (Rudd 2001), which implies a recreational diving benefit from the creation of marine protected areas (MPAs). The increase in biomass of harvested species inside MPAs is often confused as evidence of an overall increase in biomass in the stock, which in turn has led to proposals for MPAs to be used as management tools for improving stock status. This is despite the typical absence of any net biomass increase due to the problem of displaced catch and a lack of net spillover benefit (Buxton et al. 2014). An exception to this general case occurs where there is ineffective management and extreme overfishing so that effort displaced by an MPA does not result in increased catch. This can lead to the unusual situation of a net spillover benefit from MPAs, as detected with the spiny lobster Palinurus elephas around the Columbretes Islands MPA in Spain (Goni et al. 2010).

ECOSYSTEM INTERACTIONS WITH CRUSTACEAN FISHERIES Crustacean fishery management needs to take into account both the effect of the environment on the fishery and the effect of the fishery on the environment. Environmental impacts of crustacean fisheries are commonly categorized into five areas for the purposes of assessment and reporting. These are bycatch (discarded), byproduct (retained bycatch), habitat impacts, ecosystem interactions, and TEPS (threatened, endangered, and protected species) interactions. Trawl fisheries for shrimp (Ye et al. 2000) and squat lobsters (Queirolo et al. 2011) are especially scrutinized because many have large bycatch and habitat interactions relative to other fisheries (Alverson et  al. 1994). An extensive research effort reduced these impacts with approaches that include spatial management, fleet reduction, and gear modification, in particular the incorporation of bycatch reduction devices into the trawl (Al-​Baz and Chen 2015). Bycatch reduction devices include rigid separators to reduce fish bycatch used in many regions (Isaksen et al. 1992) as well as turtle excluder devices in shrimp trawl fisheries in the Gulf of Mexico (Mitchell et al. 1995). Environmental changes also affect the production of crustacean fisheries and the resultant variation in productivity through time challenges many fishery management systems. The effect of climate variation and change on krill production is a significant concern given the scale of these fisheries and their potential for ecological interaction (Richerson et al. 2017). Several large changes in distribution and production of fisheries have been reported, such as the effect of low oxygen zones on red squat lobster Pleuroncodes monodon off Chile (Gallardo et al. 2017) and brown shrimp (Farfantepenaeus aztecus) in the Gulf of Mexico (O’Connor and Whitall 2007), while extreme heat waves have led to high mortality of king prawn Penaeus latisulcatus, tiger prawn P. esculentus, and blue swimmer crabs Portunus armatus (Caputi et al. 2016). Managing fisheries in systems with these types of changes requires both and good continuous data collection to detect changes and flexible harvest strategies to respond (Caputi et al. 2016). Another especially significant issue is the effect of human development on estuarine and coastal ecosystems. Examples include impacts on Arabian Gulf shrimp fisheries from changes to salinity and water flows resulting from numerous dams on the Tigris and Euphrates Rivers (Bishop et al. 2011, Al-​Yamani et al. 2017) and the impacts of pollution on the recruitment of crabs in the Yangtze River ( Jiang et al. 2014). Ecosystem interactions with other fisheries or species have also affected production of some crustacean fisheries. Depletion of Atlantic cod Gadus morhua by fishing in the Gulf of Maine appears to have contributed to increases in the production of American lobster Homarus americanus (Zhang et  al. 2012), while depletion of the southern rock lobster Jasus edwardsii in Tasmania, Australia, has released urchins from predation, which in turn led to overgrazing and loss of lobster reef habitat (Plagányi et  al. 2018). Management actions to move ecosystems to a more natural state by increasing the abundance of sea otters Enhydra lutris in the northeast Pacific Ocean have led to the decline of a number of invertebrate fisheries, including those for Dungeness crabs Metacarcinus magister (Harbo et al. 2006).

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EMERGING ISSUES Changes in society, markets, technology, and the environment can be expected to change the future of crustacean fisheries as per most other industries. The evolution of markets and product forms will be driven by changes in the global economy, especially the rise of wealth and demand in Asia (Fig. 1.7). Consumers increasingly select products that are produced responsibly across a range of criteria, including ecosystem impacts, labor inputs, chemical contaminants, natural toxin levels, greenhouse gas emissions, and animal welfare. Many consumers are skeptical and confused by the complexity of the issues and claims, which creates an operating environment where third-​party certification becomes increasingly important. Technological developments will assist with transparency, such as the tracking of product through supply chains with blockchain technology. Despite enormous efforts over many decades, very few crustacean fisheries are performing at an optimal level in terms of their potential benefit to the community owners of the resource. This gap between current and optimal performance means that there is an opportunity for future growth to the benefit of crustacean fisheries. Every overfished crustacean stock represents an opportunity for higher future production, provided management improves. The sustainability of crustacean fisheries needs to be seen as the basic minimum level of acceptable management with more ambitious targets being pursued, such as maximizing the food, employment, or

Fig. 1.7. Supply chains for seafood in Asia such as these blue swimmer crabs landed at a fishing village in Java, Indonesia, are changing in response to greater wealth and reliability of transport routes. See a color version of this figure in the centerfold.



Crustaceans as Fisheries Resources

economic benefit from the resource. Further development is also needed in governance around the flow of benefits to ensure that harvests of public crustacean fishery resources benefit the public owners.

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Headley, M., J.C. Seijo, A., Hernández, C.J. Alfonso, and V.P. Raúl. 2017. Spatiotemporal bioeconomic performance of artificial shelters in a small-​scale, rights-​based managed Caribbean spiny lobster (Panulirus argus) fishery. Scientia Marina 81:67–​79. Huang, P. 2015. An inverse demand system for the differentiated blue crab market in Chesapeake Bay. Marine Resource Economics 30:139–​156. Huang, P., R.T. Woodward, M.J. Wilberg, and D. Tomberlin. 2015. Management evaluation for the Chesapeake Bay blue crab fishery: an integrated bioeconomic approach. North American Journal of Fisheries Management 35:216–​228. Isaksen, B., J.W. Valdemarsen, R.B. Larsen, and L. Karlsen. 1992. Reduction of fish by‐catch in shrimp trawl using a rigid separator grid in the aft belly. Fisheries Research 13:335–​352. Jiang, J., G. Feng, L. Zhang, J. Hou, G. Yang, and P. Zhuang. 2014. Preliminary assessment on habitat suitability of Eriocheir sinensis spawning crabs in Yangtze River estuary. Marine Fisheries 36:232–​238. Jimoh, A.A., I.P. Lemomu, E.J. Ansa, and H. Fashina-​Bombatta. 2010. Shellfish resources in Nigeria. Pages 683–​693 in E. Ndimele, editor. Proceedings of the 25th annual conference of the Fisheries Society of Nigeria, Lagos, Nigeria. Jin, M., Q.C. Zhou, W. Zhang, F.J. Xie, J.K. ShenTu, and X.L. Huang. 2013. Dietary protein requirements of the juvenile swimming crab, Portunus trituberculatus. Aquaculture 414:303–​308. Kittinger, J.N. 2013. Participatory fishing community assessments to support coral reef fisheries comanagement. Pacific Science 67:361–​381. Kompas, T., C.M. Dichmont, A.E. Punt, A. Deng, T.N. Che, J. Bishop, P. Gooday, Y. Ye, and S. Zhou. 2010. Maximizing profits and conserving stocks in the Australian northern prawn fishery. Australian Journal of Agricultural and Resource Economics 54:281–​299. Korzun, Y., and N.N. Zhuk. 2015. Comparative studies of krill catches from the trawls of different model types. Proceedings of the Southern Scientific Research Institute of Marine Fisheries and Oceanography 53:178–​183. Kruse, G.H. 1993. Biological perspectives on crab management in Alaska. Pages 355–​384 in G.H. Kruse, D.M. Eggers, R.J. Marasco, C. Pautzke, and T.J. Quinn II (editors). Proceedings of the international symposium on management strategies for exploited fish populations, University of Alaska Sea Grant College Program Report 93-​02, Fairbanks. Kruse, G.H., F.C. Funk, H.J. Geiger, K.R. Mabry, H.M. Savikko, and S.M. Siddeek. 2000. Overview of state-​ managed marine fisheries in the central and western Gulf of Alaska, Aleutian Islands, and southeastern Bering Sea, with reference to Steller sea lions. Alaska Department of Fish and Game, Division of Commercial Fisheries, Regional Information Report 5J00-​10, Juneau. Lee, D.E., S.G. Hosking, and M. du Preez. 2014. A choice experiment application to estimate willingness to pay for controlling excessive recreational fishing demand at the Sundays River estuary, South Africa. Water South Africa 40:39–​48. López-​Tristani, A., C.E. Lehner, M.A. Wilson, M. Ferrigno, L. Vaicekavicius, J. Kraemer, V. Robles, E.M. Hart, and J.J. Weber. 2004. Pages 1–​38 in High prevalence of dysbaric osteonecrosis among Puerto Rican seafood divers. Undersea and Hyperbaric Medical Society Annual Scientific Meeting, June 25–​29, 2004. Sydney, Australia. Mapfumo, B. 2013. Seafood markets in Southern Africa: Potential of regional trade and aquaculture development. GLOBEFISH Research Programme 109:1–​53. Mardle S., S. Pascoe, J. Boncoeur, B. Le Gallic, J. Garcia-​Hoyo, I. Herrero, R. Jimenez-​Toribio, C. Cortes, N. Padilla, J.R. Nielsen, and C. Mathiesen. 2002. Objectives of fisheries management: Case studies from the UK, France, Spain and Denmark. Marine Policy 26:415–​428. Mitchell, J.F., J.W. Watson, D.G. Foster, and R.E. Caylor. 1995. The Turtle Excluder Device (TED): A guide to better performance. Pages 1–​38, in NOAA, editor. NOAA Technical Memorandum NMFS-​SEFSC-​366. National Oceanic and Atmospheric Administration, Maryland, USA. Moffett, C., Y. Chen, and M. Hunter. 2012. Preliminary study of trap bycatch in the Gulf of Maine’s northern shrimp fishery. North American Journal of Fisheries Management 32:704–​715. Mullowney, D.R.J., E.G. Dawe, E.B. Colbourne, and G.A. Rose. 2014. A review of factors contributing to the decline of Newfoundland and Labrador snow crab (Chionoecetes opilio). Reviews in Fish Biology and Fisheries 24:639–​657.

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Fisheries and Aquaculture Muzzarelli, R.A.A. 2010. Chitins and chitosans as immunoadjuvants and non-​allergenic drug carriers. Marine Drugs 8:292–​312. Norman-​Lopez, A., S. Pascoe, O. Thebaud, I. van Putten, J. Innes, S. Jennings, A. Hobday, B. Green, and E. Plaganyi. 2014. Price integration in the Australian rock lobster industry: Implications for management and climate change adaptation. Australian Journal of Agricultural and Resource Economics 58:43–​59. NPFMC (North Pacific Fishery Management Council). 2011. Fishery management plan for Bering Sea/​ Aleutian Islands king and tanner crabs. North Pacific Fishery Management Council, Anchorage, Alaska, USA. O’Connor, T., and D. Whitall. 2007. Linking hypoxia to shrimp catch in the northern Gulf of Mexico. Marine Pollution Bulletin 54:460–​463. Ogawa, C.Y., K. Hamasaki, S. Dan, and S. Kitada. 2011. Fishery biology of mud crabs Scylla spp. at Iriomote Island, Japan: Species composition, catch, growth and size at sexual maturity. Fisheries Science 77:915–​927. Orensanz, J.M.L., J. Armstrong, D. Armstrong, and R. Hilborn.1998. Crustacean resources are vulnerable to serial depletion—​The multifaceted decline of crab and shrimp fisheries in the Greater Gulf of Alaska. Reviews in Fish Biology and Fisheries 8:117–​176. Pereira, G., and H. Josupeit. 2017. The world lobster market. GLOBEFISH Research Programme 123:1–​31. Philp, H., A. Albalat, and G. Marteinsdottir. 2015. Live holding of Nephrops norvegicus (Linnaeus, 1758) in land-​based facilities: Health and condition effects. Marine Biology Research 11:603–​612. Piasecki, W., Z. Glabinski, P. Francour, P. Koper, G. Saba, A.M. García, V. Ünal, P.K. Karachle, A. Lepetit, R. Tservenis, Z. Kızılkaya, and K.I. Stergiou. 2016. Pescatourism—​A European review and perspective. Acta Ichthyologica et Piscatoria 46:325–​350. Pinkerton, E., and D.N. Edwards. 2009. The elephant in the room: The hidden costs of leasing individual transferable fishing quotas. Marine Policy 33:707–​713. Plagányi, É.E., R. McGarvey, C. Gardner, N. Caputi, D. Dennis, D., S. de Lestang, K. Hartmann, G. Liggins, A. Linnane, E.I. van Putten, B. Arlidge, B. Green, and C. Villanueva. 2018. Overview, opportunities and outlook for Australian spiny lobster fisheries. Reviews in Fish Biology and Fisheries 28:57–​87. Queirolo, D., K. Erzini, C.F. Hurtado, M. Ahumada, and M.C. Soriguer. 2011. Alternative codends to reduce bycatch in Chilean crustacean trawl fisheries. Fisheries Research, 110:18–​28. Richerson, K., J.A. Santora, and M. Mangel. 2017. Climate variability and multi-​scale assessment of the krill preyscape near the North Antarctic Peninsula. Polar Biology 40:697–​711. Rudd, M.A. 2001. The non-​extractive economic value of spiny lobster, Panulirus argus, in the Turks and Caicos Islands. Environmental Conservation 28:226–​234. Ryder, J., K. Iddya, and L. Ababouch. 2014. Assessment and management of seafood safety and quality: Current practices and emerging issues. FAO Fisheries and Aquaculture Technical Paper 574. Food and Agriculture Organization of the United Nations (FAO), Rome, Italy. Steneck, R., A.M. Parma, B. Ernst, and J.A. Wilson. 2017. Two lobster tales: Lessons from the convergent evolution of TURFs in Maine (USA) and the Juan Fernández Islands (Chile). Bulletin of Marine Science 93:13–​33. Sumaila, U.R., and M. Dominguez-​Torreiro. 2010. Discount factors and the performance of alternative fisheries governance systems. Fish and Fisheries 11:278–​287. Sundelöf, A., V. Grimm, M. Ulmestrand, and Ø Fiksen. 2015. Modelling harvesting strategies for the lobster fishery in northern Europe: The importance of protecting egg-​bearing females. Population Ecology 57:237–​251. Tully, O. 2001. Impact of the v-​notch technical conservation measure on reproductive potential in a lobster (Homarus gammarus L) fishery in Ireland. Marine and Freshwater Research 52:1551–​1557. Ulven, S.M., B. Kirkhus, A. Lamglait, S. Basu, E. Elind, T. Haider, K. Berge, H. Vik, and J.I. Pedersen. 2010. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteers. Lipids 45:37–​46. UN Comtrade. 2016. United Nations comtrade database. United Nations, editor. United Nations Publications Board, New York, USA. Accessed April 8, 2019. [https://​comtrade.un.org/​]. van Putten, I., and C. Gardner. 2010. Lease quota fishing in a changing rock lobster industry. Marine Policy 34:859–​867.



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Bradley G. Stevens and Thomas J. Miller

Abstract The principal crab fisheries around the world are reviewed with regard to patterns of exploitation and existing management systems. Thirty-​five species and thirty fisheries were evaluated using a series of sustainability indexes based on landings, biological information, and assessment data. Indexes were scored as Good, Fair, or Poor, adapting the traffic light approach of Caddy et  al. (2005). Examples include Jonah crab (Cancer borealis), for which landings have increased by a factor of 6.5 since 2000 (Poor); gazami (Portunus trituberculatus), which supports the largest crab fishery in the world (Fair); and blue crab (Callinectes sapidus), which has had stable landings for decades (Good). Management systems that incorporate stock assessment, biological information, and rights-​based management (quota systems) generally outperform those without such attributes. Challenges for sustainable management were identified, including selective harvest (especially use of minimum size limits), climate change and its impacts on reproduction, and bycatch and discard mortality. Conserving populations and sustaining fisheries will require solving these problems in the near future.

INTRODUCTION Crabs are a highly prized seafood commodity around the world and are some of the most valuable seafood landed. Worldwide, landings have been reported for at least 55 crab species (FAO 2017a) representing 12 different families: the Galatheidae (6 species), Lithodidae (12), Cancridae (6), Geryonidae (6), Oregoniidae (8), Cheiragonidae (1), Platyxanthidae (1), Menippidae (1), Polybiidae (2), Portunidae (10), Ucididae (1), and Varunidae (1) (Tables 2.1 and 2.2). Together, these species support fisheries in shallow estuarine and coastal habitats and in deep shelf seas. Crab fisheries can differ widely in scale, from those conducted by artisanal fishers with dip nets, to those Bradley G. Stevens and Thomas J. Miller, Crab Fisheries In: Fisheries and Aquaculture. Edited by: Gustavo Lovrich and Martin Thiel, Oxford University Press (2020). © Oxford University Press. DOI: 10.1093/oso/9780190865627.003.0002

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Fisheries and Aquaculture Table 2.1.  Species of anomuran crabs fished commercially and tons captured in 2015 (from FAO 2017a). * No recent landings reported. Family Galatheidae

Genus

Species

Common name

Cervimunida Munida Pleuroncodes Pleuroncodes Galatheidae

johni gregaria monodon planipes spp.

Blue squat lobster Swarming squat lobster Carrot squat lobster Pelagic red crab Craylets, squat lobsters

aequispina maja murrayi santolla

Golden king crab Northern stone crab Subantarctic stone crab Southern king crab

brevipes camtschaticus platypus

Hanasaki king crab Red king crab Blue king crab

formosa granulosa spinosissima verrilli

Globose king crab Softshell red crab Antarctic stone crab Red vermillion crab

Tons 12,580 4,517 * 6,267 964 832

Lithodidae Lithodes

13,371

Paralithodes

24,625

Paralomis

All

3,256 * * 10,115 974 16,810 6,841 1,995 * 1,995 * * 52,571

conducted by large commercial boats with up to a dozen crew who stay out at sea for weeks at a time. The crabs that are harvested can be sold live, both as hardshell and softshell crabs, killed and processed whole, or killed and processed for crab meat. Here, we review the principal crab fisheries around the world and present selected case studies on assessment and management. For each crab species, we highlight aspects of the species biology and distribution as they pertain to fisheries for the species, provide a summary of patterns and levels of exploitation, and summarize the management system that is currently in place. Also, we estimate stock status of those crab fisheries with recent landings >1,000 t, relative to the history of each fishery, using a series of sustainability indexes, and evaluate them by adapting the traffic light approach developed by Caddy et al. (2005). Crab Fishery Status In the following discussion of the primary crab fisheries globally, we have adapted the traffic light approach of Caddy et al. (2005) to evaluate the status of major crab fisheries. Two sets of indexes were created, the first based on landings data and the second on information quality. Landings were used as the measure of abundance, even though these are subject to controls and closures, because many populations have no regular assessment. Three indexes based on landings were created



Crab Fisheries Table  2.2. Species of  brachyuran crabs fished commercially and production (tons) in 2015 by genus.* Aquaculture production. Family Brachyura

Genus All

Cancridae

Cancer

Species

Common name

Unspecified

Marine crabs

borealis irroratus pagurus productus

Jonah crab Atlantic rock crab Edible crab Pacific rock crab

magister edwardsii

Dungeness crab Mola rock crab

affinis fenneri longipes maritae notialis

Deep-​sea red crab Golden deepsea crab Mediterranean geryon West African geryon Southwest Atlantic red crab Red deepsea crab Chaceon unknown

Metacarcinus

Geryonidae

Chaceon

Portunidae Portunidae

15,122 3,905 6,492

Chionoecetes

Maja Mithrax Cheiragonidae Erimacrus Platyxanthidae Homalaspis Menippidae Menippe Polybiidae Necora Polybius

6,154 5,364 48,408 994 19,027

quinquedens spp. Oregoniidae

Tons 2,769,935 323,968 60,920

290 143 120 3,552 588 1,613 186 253,313

angulatus bairdi japonicus opilio tanneri spp. squinado armatus isenbeckii plana mercenaria puber henslowii

Triangle Tanner crab Tanner crab Red snow crab Snow (Queen) crab Grooved tanner crab Spinous spider crab Harbour spider crab Hair crab Giant stone crab Black stone crab Velvet swimming crab Henslow’s swimming crab

All Callinectes

90 mm CL), and sets additional rules regarding legal males (NPFMC [North Pacific Fisheries Management Council] 2015). The MLS for Bristol Bay RKC (males) is 135 mm CL. Landings of North Pacific RKC were about 8,000 t in 2015 (Table 2.2), with mean catch per unit effort (CPUE) of 31 crabs per pot (CPP), after which the Acceptable Biological Catch (ABC) was set at 6,060 t and the TAC at 5,440 t. This fishery has a Fair rating for landings and biological indexes, for an overall rating of Fair (Table 2.3). A Russian fishery around the Kamchatka Peninsula peaked at 55,000 t in 1995. Much of the fishing in that region was suspected to be illegal, unreported, or unregulated (IUU) and contributed to overfishing and subsequent collapse of the Kamchatka fishery (Otto 2014). Russian processing

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Table 2.3A.  Condition indexes for wild capture crab fisheries with mean landings >1,000 t, as indicated by color: Good (white), Fair (gray), or Poor (dark gray). Last Yr and Last t are most recent year and landings. Avg and max are average and maximum landings in metric tons. SD, standard deviation; N, years with catch >0; CV, coefficient of variation (a measure of volatility); Max/​avg is the ratio of maximum to mean landings (a measure of amplitude); Last/​avg is the ratio of the most recent landings to long-​term mean landings. Summary is an overall predictor of stock condition. Traffic light approach adapted from Caddy et al. (2005). Region

Species

Last year Last t

Average Maximum SD

N

CV

United States Caribbean US (NW Atlantic) NE Atlantic Red deep-​sea crab West African Geryon SW Atlantic Geryon China US (Bering Sea) Japan Canada (NW Atlantic) US (Bering Sea) Japan S. Korea US (Bering Sea) Chile & Argentina US (Atlantic) Chile

Callinectes sapidus Callinectes sapidus Cancer borealis Cancer pagurus Chaceon quinquedens Chaceon maritae Chaceon notialis Charybdis spp. Chionoecetes bairdi Chionoecetes japonicus Chionoecetes opilio Chionoecetes opilio Chionoecetes spp. Chionoecetes spp. Lithodes aequispinus Lithodes santolla Menippe mercenaria Metacarcinus edwardsii

2016 2016 2015 2015 2015 2015 2015 2015 2016 2015 2015 2016 2015 2015 2016 2015 2014 2016

83,477 29,780 1,818 30,051 1,627 1,637 2,271 20,726 6,297 12,523 56,094 45,411 6,669 12,964 3,059 2,584 1,595 4,302

67 53 42 26 43 40 23 36 36 36 46 38 36 36 35 55 67 23

0.268 0.742 2.248 0.916 1.475 1.475 1.350 2.736 2.464 1.790 1.134 1.924 0.799 2.477 0.935 2.005 1.364 0.545

97,896 26,114 6,154 48,408 1581 3552 588 58,392 8,918 16,900 93,519 18,438 4,400 43562 1,650 10,115 902 4,316

129,570 29,780 7,733 48,408 4,003 4,226 5,259 64,927 30,259 29,627 106,766 179,685 14,220 43,562 6,691 11,012 3,214 6,974

22,349 8,687 2,044 13,760 957 1,208 1,532 28,353 7,758 11,206 31,807 43,696 2,665 16,057 1,430 2,590 1,088 1,173

Maximum/​ average 1.55 2.54 2.13 0.81 1.23 1.29 1.16 1.57 2.40 1.18 0.95 1.98 1.07 1.68 1.09 2.13 1.01 0.81

Last/​ average 1.173 2.231 2.121 1.334 0.048 1.586 1.098 1.328 0.338 0.391 1.177 0.617 0.851 1.906 0.986 2.907 0.637 0.012

Summary 0.998 1.839 2.165 1.018 0.818 1.451 1.202 1.877 1.735 1.121 1.087 1.507 0.906 2.021 1.005 2.347 1.003 0.456

Alaska US (Pacific) Norway Russia (Barents Sea) Russia (Pacific) US (Bering Sea) US (Bering Sea) Chile China Southeast Asia Southeast Asia Southeast Asia

Metacarcinus magister Metacarcinus magister Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes platypus Paralomis granulosa Portunus pelagicus Portunus pelagicus Portunus trituberculatus Scylla serrata

2014 2015 2015

2,442 19,953 2,175

2,324 13,961 1,289

3,913 37,094 5,613

695 9,275 1,517

25 45 22

0.598 1.329 2.353

0.84 1.33 2.18

0.169 0.646 0.584

0.536 1.101 1.705

2015

6,397

4,691

12,938

3,952

17

1.685

1.38

0.432

1.165

2015

8,238

26,068

54,986

14,467

66

1.110

1.05

1.232

1.132

2015

7,952

22,683

84,198

19,942

57

1.758

1.86

0.739

1.451

2011 2015 2015 2015 2015 2015

854 1,966 83,766 77,809 560,811 33,462

2,215 2,079 36,966 67,416 251,420 19,187

8,138 6,527 83,877 89,569 605,629 43,550

2,022 1,454 29,719 16,485 156,883 10,994

28 38 36 36 36 36

1.826 1.398 1.608 0.489 1.248 1.146

1.84 1.57 1.13 0.66 1.20 1.13

0.673 0.078 1.575 0.630 1.972 1.298

1.445 1.015 1.439 0.595 1.475 1.193

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Table 2.3B.  Condition indexes for wild capture crab fisheries, based on biological data, indicated by color: Good (white), Fair (gray), or Poor (dark gray). Indicators for Biomass, Biology, MLS (minimum legal size), TAC, F or M, and Bmsy are 1 if well known, 2 if estimated or based on poor information, and 3 if unknown. Avg-​2 is the mean value of Biological indicators. Final is the unweighted average of Stock indexes (Table 2.3A) and Biological indexes. Species lacking sufficient information have been omitted. Region United States Caribbean US (NW Atlantic) NE Atlantic Red deep-​sea crab West African Geryon US (Bering Sea) Canada (NW Atlantic) US (Bering Sea) US (Bering Sea) Chile & Argentina US (Atlantic) Chile Alaska US (Pacific) Norway Russia (Barents Sea) Russia (Pacific) US (Bering Sea) US (Bering Sea)

Species Callinectes sapidus Callinectes sapidus Cancer borealis Cancer pagurus Chaceon quinquedens Chaceon maritae Chionoecetes bairdi Chionoecetes opilio Chionoecetes opilio Lithodes aequispinus Lithodes santolla Menippe mercenaria Metacarcinus edwardsii Metacarcinus magister Metacarcinus magister Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes camtschaticus Paralithodes platypus

Biomass 1 3 3 3 2 2 1 1 1 3 2 1 3 3 3 1 1 2 1 2

Biology 1 2 2 1 3 2 1 1 1 2 1 1 1 2 1 1 1 1 1 2

MLS 1 2 2 1 2 2 1 1 1 1 1 1 2 1 1 1 1 1 1 1

TAC 1 3 3 2 1 1 1 1 1 2 1 1 3 3 3 1 1 2 1 1

F or M 1 2 3 1 2 1 2 1 1 3 3 1 3 3 3 2 2 2 1 3

Bmsy 1 3 3 1 2 2 2 1 2 3 3 1 3 3 3 3 3 2 2 3

AVG-​2 1.00 2.50 2.67 1.50 2.00 1.67 1.33 1.00 1.17 2.33 1.83 1.00 2.50 2.50 2.33 1.50 1.50 1.67 1.17 2.00

Final 1.00 2.17 2.42 1.26 1.41 1.56 1.53 1.04 1.34 1.67 2.09 1.00 1.48 1.52 1.72 1.60 1.33 1.40 1.31 1.72



Crab Fisheries (A)

(B)

(C)

Fig. 2.1. A. Typical Bering Sea crab fishing boat, with crab pots on deck. Note crane for handling pots. (http://​www. fv-​saga.com/​). B. Standard Bering Sea crab pot, with tunnel entrances suspended from roof, coiled rope, and buoys (B. Stevens). C. Chesapeake Bay blue crab fishing boat retrieving a pot from the water (https://​www. chesapeakebay.net).

vessels participated in joint-​venture fisheries with US catcher vessels in the Bering Sea from 1978 to 1995. Although biological parameters are well known, survey data are unavailable. Lacking proof of IUU fishing, the RKC fishery along the Russian Pacific coast was given a Fair landings index, a Fair biological index, and a Fair overall rating (Table 2.3).

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Fisheries and Aquaculture Fishery Asia Barents Chile Russia 100000

S_Atl

50000

Landings (t)

US

0

30

1950

1960

1970

1980 Years

1990

2000

2010

Fig. 2.2. Landings of Lithodid crab species, by region 1950–​2015 (data from FAO).

A directed fishery for Aleutian Islands GKCs began in 1981. High ERs (>20%) led to declines in landings, mean size, and mean weight (Leon et al. 2017). Landings in 2016 were 1,650 t. Landing indexes for this fishery are Good, but biological indexes are Poor, for an overall rating of Fair (Table 2.3). Blue king crabs (BKCs) were fished in the Bering Sea prior to 1999 (Leon et al. 2017), and scarlet king crab L. couesi are captured as bycatch in the GKC fishery. Due to low landings and lack of assessment, these fisheries were not rated. All Alaskan crab pot fisheries discard females and undersize specimens of target species and nontarget species. Bycatch ratios (biomass of discards relative to landings of legal crabs) in the Bering Sea in 2010 were 1.37, 1.54, and 0.8 for red, blue, and GKC, respectively (Stevens 2014). Southern King Crabs A fishery for the southern king crab (centolla) was developed in Chile in the late 1970s and expanded in the 1990s. The reproduction, size at maturity, fecundity, development, and growth of this stock is well known (see review by Lovrich and Tapella 2014). Landings from the Beagle Channel, Tierra del Fuego, declined dramatically in the mid-​1990s, leading to a partial fishery closure from 1994 to 2013 due to reduced catches, size, and reproduction. Nevertheless, illegal fishing has occurred continuously and probably contributes to low abundance. Inconsistent regulations between Chile and Argentina contribute to illegal landings, especially in the Beagle Channel (Varisco et al. 2018). In contrast, landings from the Golfo San Jorge increased rapidly after 2002 because of improved technology and larger vessels, producing an overall increase in landings, and combined landings from both countries reached a peak of 13,000 t in 2013. Crabs are predominantly fished using strings of up to 150 conical pots with escape vents and may be cooked and frozen onboard (Varisco et al. 2018);



Crab Fisheries

only males >110 CL may be landed, from January through April, and a TAC of 2,000 t was suggested in 2017. Over the long term, landings have fluctuated in response to demand as Alaskan fisheries wavered. Increasing capitalization and effort have led to increased landings but reduced yields. In the Southern Ocean, a fishery for Paralomis spp. and Lithodes murrayi developed in the mid-​1990s as that for centolla declined in Tierra del Fuego, but it has produced very low landings since that time. Though the collapsed Beagle Channel fishery and the Golfo San Jorge fisheries are quite different, their combined fisheries were given ratings of Fair (Landings) and Fair (Data) for an overall rating of Fair (Table 2.3). Barents Sea King Crab Fisheries Red king crabs were transplanted to the Barents Sea coast of Russia in the late 1960s, and by 1990 had expanded into Norwegian waters, where they were considered a nuisance due to entanglement in lumpfish and cod nets (Sundet 2014). The population grew exponentially until 2004, after which it declined both due to heavy fishing and severely depleted food sources. A fishery developed in 1994 and has been managed separately in two regions with distinctly different goals. In eastern Finnmark (east of North Cape at 26°E), a regulated fishery is managed for sustainability under a TAC and limited entry, whereas in west Finnmark an open unregulated fishery exists, and fishers are encouraged to catch and remove as many RKC as possible to prevent them from spreading down the east coast of Norway. Both Russian and Norwegian vessels participate in the fishery, which has a MLS of 130 mm CL (Norway) or 150 mm CL (Russia) (ICES 2015). Only males are landed in Russia, but a small number of females are landed in Norway. Trap design is prescribed in both countries, including escape vents (Norway) and biodegradable panels (Russia). The Norwegian Institute of Marine Research (IMR) conducts stock assessment cruises in east Finnmark (regulated) and a trap survey in west Finnmark (unregulated). These data indicate that the unregulated fishery is successful at limiting the abundance and spread of crabs (Sundet 2014). Landings during the period 2010–​2015 have been stable at about 1,000–​1,300 t in the Norwegian area, with total landings in the ICES region of about 8,570 t in 2015. The Norwegian fishery employs >500 vessels of 70 mm CW in the south, over a temperature gradient of 4–​5°C (Somerton 1981). A similar east-​west size gradient in the Gulf of Saint Lawrence (GSL) is associated with a 250% increase in fecundity (Sainte-​Marie et al. 2008). Snow crabs are adapted to extremely cold water and tend to live in the range from –​1.8°C to 2°C, in a tongue of cold-​pool water that extends eastward from the western Bering Sea shelf edge, whereas Tanner crabs (C. bairdi) occur outside the cold pool at temperatures of 2–​6°C. An ontogenetic migration of adult snow crabs occurs from the northeastern portions of the Bering Sea shelf to the southwest (Ernst et al. 2005). Tanner crabs reach maturity at 5–​6 years of age in the GoA (Donaldson et al. 1981). Female snow crabs typically reach maturity at sizes 30–​50 mm smaller and 2–​3 years earlier than male crabs (Sainte-​Marie et al. 2008). Estimates of life span after the maturity molt, based on radiometric aging, are 5 years for C. bairdi, 6.8 years for C. opilio in the Bering Sea (Ernst et al. 2005), and 7.8 years for an unfished population of male C. opilio in the GSL (Fonseca et al. 2008). Snow crab mating systems are complex. Primiparous females mate at the maturity molt and extrude clutches soon after mating (Sainte-​Marie et al. 2008), whereas multiparous females producing their second or later clutch are 32% more fecund (Somerton and Meyers 1983). Mating by primiparous and multiparous females is disjunct in both space and time, with the former mating earlier and in shallower water than the latter. Females may fertilize a second clutch with stored sperm or mate in the hard-​condition (Elner and Beninger 1992), but fertility declines over time (A.J. Paul



Crab Fisheries

1984). In the Bering Sea, most females carry eggs for 15 (primiparous) or 12 (multiparous) months and can produce four to six lifetime broods, whereas in the GSL, most females carry eggs for 27 or 25 months, respectively, so produce only two or three lifetime broods (Sainte-​Marie et al. 2008). Male Chionoecetes sp. acquire proportionally larger chelae at the terminal molt, which can occur over a wide range of sizes (Conan and Comeau 1986, Stevens et al. 1994, Sainte-​Marie et al. 1995). Prior to the pubertal molt, males have small claws, so they are morphologically immature (MI); adult males with larger claws are morphologically mature (MM) (Sainte-​Marie et al. 2008). Males are typically about 30% larger than their mates (Stevens et al. 1993). Although large MI males can mate, the majority of successfully mating males are hardshelled and MM (Stevens et al. 1993, A.J. Paul et al. 1995). Mating is highly competitive, and sperm competition and rationing occur as the operational sex ratio (OSR, male:female) decreases (Sainte-​Marie et al. 1999, Rondeau and Sainte-​ Marie 2001). Females form dense aggregations of haystack-​like mounds during larval release in spring that are associated with high tidal currents (Stevens et al. 1994, 2000, Stevens 2003). Episodic recruitment occurs in both the Bering Sea and eastern Canada populations. Southern Tanner Crab Fisheries Fisheries for Tanner crab began in the GoA and the EBS in 1967 and peaked in the late 1970s, then declined rapidly (Fig. 2.3A). The fishery was closed from 1990 to 2005, and the larger EBS fishery was closed during the periods 1986–​1987, 1997–​2006, and 2011–​2014. The fishery for this species is closed if the abundance of large (>79 mm CW) females drops below 9,500 t. The GoA fishery was mostly conducted by small boats (30 m) vessels. Warming of EBS bottom waters has decreased the areal extent of the shelf cold pool, causing an expansion of habitat for Tanner crabs, while shrinking the habitat preferred by snow crab (Orensanz et al. 2004). Tanner crab populations (and landings) have undergone at least two large cycles of abundance in apparent synchrony with snow crab populations, indicating that recruitment in both species is probably controlled by environmental factors. Landings in 2016 were about 9,000 t, with mean catch of 38 CPP. The EBS fishery for Southern Tanner crabs has a Fair landings index and a Good biological index, for an overall rating of Fair (Table 2.3). A small amount of grooved Tanner crabs, C. tanneri, are captured as incidental bycatch in either the golden crab or snow crab fisheries, but the fishery has been closed most years since 1996. Eastern Bering Sea Snow Crab C. opilio Snow crab landings in both Atlantic and Pacific regions are highly periodic, suggesting episodic recruitment waves of alternating weak and strong year classes (Sainte-​Marie et al. 2008). Abundant year classes tend to be followed by poor year classes 5–​6 years later (Caddy et al. 2005). Peaks last 2–​6 years and occur at intervals of 6–​12 years. Proposed causative factors include environmental effects on larval survival, predation, temperature changes, cannibalism, and resource competition between successive cohorts. Fluctuations in female abundance are 10 times greater, and more variable than males, due to differences in age at maturity and life span. For the same reasons, male and female cycles are asynchronous, causing extreme changes in OSR and relative abundance of mating types (primiparous, multiparous, MI, MM), all of which can have large impacts on population fecundity (Sainte-​Marie et al. 2008). Snow crab landings from the Bering Sea commenced simultaneously with Tanner crabs in 1977. Landings were highly variable, with peaks occurring in 1991, 1998, and 2012 (Fig. 2.3A) (Leon et al. 2017). Landings in 2016 were about 18,500 t, with mean catch of 136 CPP. The MLS is 78 mm CW, but processors prefer crabs >100 mm CW. Although ER decreased from 58% to 22% of legal males, the Bering Sea snow crab stock was declared overfished in 2000. In 2001, an HCR was initiated, in which ER are dependent on surveyed spawning biomass (SB; Fig. 2.4). In 2005, the fishery was

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Fisheries and Aquaculture 10000 20000 30000 40000 50000

100000 150000 200000

(B)

0

0

50000

Landings (t)

(A)

1970

1980

1990

C. opilio US

2000

2010

C. opilio CA

2020

1980

1990

2000

C. pagurus

2010

2020

M. magister, Pacific

(D)

0

1000

2000

2000

4000

3000

6000

4000

5000

8000

(C)

Landings (t)

1970

C. bairdi

0

36

1970

1980

1990

2000

2010

2020

Year

1970

1980

1990

2000

2010

2020

Year

C. borealis

M. magister, Alaska

C. productus

M. edwardsii

C. quinquedens

C. maritae

M. mercenaria

Fig. 2.3. Landings of selected crab fisheries, 1970–​2016. A. Chionoecetes species in Alaska and eastern Canada: snow crab (Chionoecetes opilio) and Tanner crab (Chionoecetes bairdi); B. Dungeness crab (Metacarcinus magister) on the US Pacific coast and Edible crab (Cancer pagurus) in Europe; C. Jonah crab (Cancer borealis), Dungeness crab (Metacarcinus magister) in Alaska, red rock crab (Cancer productus), and Chilean edible crab (Metacarcinus edwardsii); D. Chaceon quinquedens, Chaceon maritae, and Menippe mercenaria. Data from FAO (2017a), ICES (2017), Leon et al. (2017), and PacFIN (2016).

converted from open access to a quota-​share system called “Crab Rationalization” (see the section on management of Alaskan crab fisheries), accompanied by major reductions in vessel effort and extension of the fishing season from days to months. The fishery for snow crabs typically starts on January 15 and lasts 1–​10 weeks. The EBS fishery for snow crabs has a Fair landing index due to wide fluctuations but a Good biological index, for an overall Fair rating (Table 2.3). Eastern Canada Snow Crab Snow crabs have been fished within the GSL and along the eastern shores of Nova Scotia and Newfoundland since the 1960s. Large fluctuations in abundance have occurred in this region as well as others, suggesting the existence of simultaneous hemisphere-​scale recruitment waves. Landings increased gradually due to technological improvements and expansion of fishing grounds. Landings peaked in 1982, then declined rapidly in 1989, at which time the fishery was closed

Crab Fisheries

0.2

0.4

0.6

0.8

1.0

Fofl = Fmsy or Proxy Fmsy

a

0.0

Fofl/Fmsy or Proxy Fmsy

1.2



0.0

B 0.5

1.0

1.5

B/Bmsy or Proxy Bmsy

Fig. 2.4. Harvest control rule used for Bering Sea and Aleutian Island crab fisheries, Tiers 1 through 4. Vertical line is Bcrit (critical biomass). B, biomass; Bmsy, Biomass at maximum sustainable yield; Fmsy fishing mortality at maximum sustainable yield; Fofl, fishing mortality at overfishing level (from NPFMC 2015).

(Moriyasu et al. 1998) (Fig. 2.3A). In 1990, MLS was set at 95 mm CW, and the ERs were reduced from 50-​60% to 32%, a quota system was initiated, and the Canadian Department of Fisheries and Oceans (DFO) began a trawl survey to determine annual abundance. Drastic reduction of the ER led to a buildup of old-​shell crabs and associated discard mortality, whereas intermediate rates have helped to eliminate both new-​and old-​shell discard mortality and stabilize landings. Fishers avoid areas of old-​shell crabs (“cemeteries”) in order to catch new-​shell crabs, of higher value. This fishery was rated Fair for landings and Good for biological indexes, for an overall Good rating (Table 2.3). Barents Sea and Greenland Snow crabs were first discovered in the Barents Sea in 1996 and the population has expanded rapidly since. Most of the stock is located in the Russian exclusive economic zone. Commercial fishing started in 2012, and landings increased to 8,000 t in 2015, involving 21 boats from different nations (ICES 2015). The fishery takes males only, and MLS of >95 mm CW exists only in the Norwegian zone. A fishery for snow crabs in Greenland peaked at 15,000 t in 2001, but declined rapidly, and has averaged about 2,000 t annually since 2007. European or Spinous Spider crab (Maja Spp.) European spider crabs include two species, the Atlantic spider crab, Maja brachydactyla, and the Mediterranean spider crab, M. squinado. The former occurs along the coasts of Portugal, Spain, France, and the southwest coasts of England and Ireland. Because of their similarity, they are often grouped together as a single species. Annual landings are about 5,000 t, with about 70% coming from France and about 10% from the United Kingdom. In the Mediterranean, M. squinado is commercially extinct and has been declared a protected species, although about 50 t are landed annually (FAO 2017a). Cancer Crabs (Family Cancridae) Most crabs in the family Cancridae have indeterminate growth. Females must molt before mating but generally store sperm for some interval before extruding and fertilizing a clutch. Juveniles settle in nearshore areas and grow to maturity in 4–​5 years. Chela allometry is minor, so estimates of male maturity may rely on other measures.

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Fisheries and Aquaculture Dungeness Crab (Metacarcinus magister) and Red Rock Crab (Cancer productus) Dungeness crabs typically mate in high-​salinity areas in the fall. Larvae hatch in January–​March and are transported offshore during winter; megalopae return to estuaries where they settle in May–​August (Stevens and Armstrong 1984). Along the Pacific Coast, large fluctuations in abundance have occurred at intervals of 10–​12 years, which may be due to periodicity in wind patterns or to cannibalism by early cohorts on late arrivals. Fisheries for Dungeness crabs have been reported from Chile to Alaska, although the Chilean crabs were probably misidentified Metacarcinus edwardsii (Schram and Ng 2012). In US waters, Dungeness crabs are fished in the Pacific coast states of California, Oregon, and Washington and Alaska. In all states, fisheries are managed primarily by 3-​S (size, sex: males, and season) and gear restrictions (traps with escape rings). Recent landings (2001–​2015) have averaged about 25,000 t, with 90% equally distributed among the Pacific coast states and 10% from Alaska (PacFIN 2016) (Fig. 2.3B). Alaskan landings tend to fluctuate inversely with landings along the Pacific coast and with other Alaskan crab fisheries due to price and availability (Leon et al. 2017) (Fig. 2.3C). Both of these fisheries were given a Fair rating due to cyclic behavior and lack of assessment data (Table 2.3). The Pacific red rock crab, Cancer productus, is mostly caught as bycatch in the Dungeness crab fishery or as recreational catch along the US Pacific coast. Landings have been relatively stable, at about 600 t since 1970. This fishery was not rated. Edible or Brown Crab (Cancer pagurus) The edible, or brown, crab is fished in the North and Irish Seas and coastal areas of the United Kingdom, Norway, and France. It is one of the more well-​studied crustaceans owing to its value and accessibility. Management measures include limited entry. There are no closed seasons or areas in most fishing areas, although Scotland and Ireland limit effort by kilowatt-​days (kW·d), a measure of vessel power and time (e.g., 702,292 kW·d in ICES areas V and VI). The fishery takes both male and female crabs (which dominate the catch), though there are restrictions on gravid females and soft crabs in most areas. MLS is imposed in most areas, ranging from 130 to 140 mm CW. There are restrictions on vessel size but not power. Trap limits and entrance sizes are prescribed only in France. Escape vents are required in some areas around the United Kingdom, but biodegradable panels are not. Landings in the ICES countries have increased steadily over the last two decades (ICES 2014)  (Table  2.3, Fig. 2.3B). Most of the catch comes from England (35%) and Scotland (27%). Edible crab in most of the assessment units in Scotland were fished close to or above the proxy value for Fmsy (fishing mortality at maximum sustainable yield) in 2015. Landings in France have been about 5,500 t annually for the last 15 years. Edible crab abundance has been steadily increasing northward along the Norwegian coast; landings in Norway peaked at 8,500 t in 2008 and were around 4,800 t in 2015 (ICES 2017). Although stock assessments are not routinely conducted, some success has been achieved using reference fleets (selected commercial fishing boats) that measure all crabs from a small number of standardized traps. Stable landings since 2000 allow it a Fair landings index and a Fair biological index for an overall Fair rating (Table 2.3). Chilean Edible Crab or Mola Rock Crab (Metacarcinus edwardsii) The Chilean edible crab Metacarcinus (Cancer) edwardsii has been reported from Ecuador to the Straits of Magellan and occasionally as far south as the Beagle Channel (Vinuesa et al. 1999). Similar to other Cancrids, mating occurs in spring (October–​January) after the female molts, and sperm can be stored for several months (Pardo et al. 2015). Larvae of M. edwardsii hatch in winter, develop through five larval stages, and recruit and settle in nearshore environments in late spring and summer (December) (Rojas-​Hernandez et al. 2016). High fecundity and a long planktotrophic larval period contribute to low genetic variability across space and time (Rojas-​Hernandez et al. 2016).



Crab Fisheries

The fishery for M. edwardsii is the most important artisanal fishery in Chile and is concentrated in the south (40°S to 48°S). Management measures include a MLS of 110 mm CW for both sexes, restrictions on harvesting of ovigerous females, and no seasonal restrictions (Pardo et  al. 2015). Abundant stocks in the north, where fishing pressure is low, probably help to maintain sustainability of populations over time (Rojas-​Hernandez et al. 2016). This may explain why volatility and amplitude of fluctuations are relatively low, and recent landings are identical to the long-​term mean (Table  2.3, Fig. 2.3C). As a result, fishery landings were rated Good. General biology is known, and SM50 has been estimated; physiological maturity is reached at 101 mm CW (both sexes) and morphometric maturity at 118 mm CW for males and 106 mm CW for females (Pardo et al. 2009). Compared to low-​intensity fishing areas, areas with high fishing intensity show evidence of male sperm depletion (smaller vasa deferentia), poor recovery of sperm reserves after mating, reduced sex ratio, and reduced size of males, all of which may have detrimental impacts on population reproduction (Pardo et al. 2015). There is no stock assessment information (or TAC) or biological reference points (BRPs; Bmsy, M, F, etc.), so the overall fishery was rated Fair. Jonah Crab (Cancer borealis) and Rock Crab (C. irroratus) Jonah crabs range from Newfoundland to Florida and are mostly caught as incidental bycatch in the American lobster fishery, so the fisheries have been co-​managed (ASMFC 2015). Crabs have similar life history to other Cancer crabs and may migrate inshore during spring and summer. Both sexes reach physiological maturity around 90 mm CW, and males reach larger maximum sizes (220 mm CW) than females (150  mm CW). Male chelae have allometric growth that can be used to determine morphometric maturity, which occurs near 128 mm CW on the Scotian Shelf (Moriyasu et al. 2002). Stocks are not assessed routinely, so biomass, mortality, growth, and ER are unknown. Trawl surveys indicate stable or declining abundance, but catches decline south of Cape Cod, where they prefer deeper water. Over 94% of landings occur in Massachusetts and Rhode Island, and 7,700 t in 2014 (Daly et al. 2015) (Fig. 2.3C). As a result, an amendment to the American Lobster Fishery Management Plan for Jonah crabs was established in 2016. There are no size or sex restrictions in most states, though some have established seasons or trip limits. Volatility, amplitude, and relative catch are all high, and biological data are lacking. As a result, this is the only fishery in our list that earned Poor ratings for both landings and biological indexes. A small amount of Atlantic rock crabs (C. irroratus) are landed coincident with Jonah crabs because of their similarity; landings rarely exceeded 1,000 t in most years, but jumped to >5,000 t in 2015 as bycatch in the Jonah crab fishery. This fishery was not rated. Geryonidae (Deep-​Sea Crabs) At least six species of Chaceon are fished around the North and South Atlantic Ocean. The majority of landings are made up by C. maritae, C. quinquedens, and C. notialis, with smaller contributions from C. affinis and C. fenneri. All live on the continental slopes between 250 and 2,000 m. Life history characteristics of geryonid crab species were reviewed and compared by Hastie (1995). Red Deep-​Sea Crab (Chaceon quinquedens) The red deep-​sea crab Chaceon quinquedens (red crab) ranges from the Gulf of Maine to the Gulf of Mexico, at depths from 200 to 1,800 m and temperatures of 5–​8°C (Stevens and Guida 2016). Northwest Atlantic stocks are considered to be a single population, distinct from the Gulf of Mexico stock. A small US fishery exists along the continental slope from New England to North Carolina; annual landings declined from 1,600 to 930 t during 2002–​2013, with a mean of 1,570 t

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Fisheries and Aquaculture (Stevens and Guida 2016). Red crab is a data-​poor stock; very little is known about their biology, abundance, growth, age, or reproduction. Because of their depth, red crab abundance is not routinely assessed, but population estimates made using towed camera systems (Wigley et  al. 1975, Wahle et al. 2008) showed a 42% decline in large males in the 350-​to 500-​m depth zone after a decade of targeted harvesting on males, despite a 250% increase in overall biomass (mostly due to juveniles) (Weinberg and Keith 2003). The size of landed crabs has declined from 114 mm CW to 74 mm CW) in 2008 was 47,800 t, and estimated MSY for large males (≥114  mm CW) was about 2,500 t.  Landings were fluctuating (Table 2.3, Fig. 2.3D). The fishery is rated Good, but overall rating is only Fair due to lack of biological information (Table 2.3). Other Chaceon The largest geryonid fishery is that for Chaceon maritae off the coast of West Africa (Namibia) (Beyers 1994). As of 1994, fishing occurred year round, with a TAC of 6,000 t, but vessels were limited to 3,000 traps and could not fish shallower than 500 m. Estimated SM50 for male C. maritae in South Africa was 93 mm CW (Melville-​Smith 1989). Estimated abundance of commercially available stock (>75 mm CW) for crabs between 17°S and 21°S was about 17,700 t, with densities ranging from 37 to 228 crab/ha (mean 98) (Beyers 1994), similar to C. quinquedens in the northwest Atlantic. Estimated F ranged from 0.05 to 0.19. Landings peaked in 2007 (Fig. 2.3D). In the Southwest Atlantic C. notialis is mainly distributed in Uruguayan waters south of 33°S and may be among the largest geryonid stock in the world. Management tools include limited entry (two vessels) and sex restrictions (males >95 mm CW). Males are most abundant in the middle of the geographic area and at depths of 1000 m, but females are more abundant in the north and at depths 50,000 t in 2014, but this amount is only a fraction of aquaculture production (FAO 2017b). The species has become invasive elsewhere due to ballast water discharge. They are now found on both the western and eastern US coast as well as in the Great Lakes and Europe, where breeding populations exist. Black-​Clawed Stone Crab (Menippe mercenaria and M. adina) The black-​clawed stone crab group includes two species, the Florida (Menippe mercenaria) and Gulf stone crabs (M. adina), which are landed as a claws-​only fishery in the southeastern United States. The fishery is small, with mean landings of 1,602 t (FFWCC 2018) (Fig. 2.3D). Florida stone crabs occur from North Carolina to Belize but are replaced by Gulf stone crabs in the northern and western Gulf of Mexico. Adults live in burrows from the shoreline to depths of 60 m and are caught with baited traps or by hand. Stone crabs recruit to the commercial fishery at age 3 (males) or 4 (females); they molt and mate in the fall and produce eggs from April through September. Only the claws of stone crabs are harvested, and the crab is returned to the water, although mortality was 28% for single amputations and 47% for double amputations (Davis et al. 1978). SM50 is 70 mm propodus length for males and 60 mm for females (Gerhart and Bert 2008). The fishery operates from October through May. In 2016, abundance of young-​of-​the-​year crabs declined to a 10-​year low. Landings have declined since 2008, coincident with a three-​fold increase in the number of traps. Females can produce several broods before reaching legal size, providing some population resilience, though low CPUE suggest the fishery is overcapitalized. This fishery has a Fair landings index and a Good biological index for an overall Good rating (Table 2.3).

STOCK ASSESSMENT AND MANAGEMENT OF CRAB FISHERIES Approaches to the management of crab fisheries are as diverse as the species exploited. Compared to finfish, which exhibit continuous growth and can be surveyed with active gear, traditional approaches to fisheries management are challenging to apply to crabs. Management regimes rely on a spectrum of information on the biology of the species exploited, its distribution and abundance in the environment, patterns and levels of catch, and increasingly, ecosystem considerations of removals of crabs from the environment. The type of management applied depends on the availability of different types of information, which can be described in a hierarchy. For small-​scale fisheries lacking annual surveys, data-​poor methods involving a fraction of the average catch are commonly employed. Some fisheries are defined as S-​fisheries (Orensanz et al. 2005) (i.e., small scale, spatially structured, sedentary, and artisanal or subsistence fisheries). In the absence of stock assessment information, they are typically managed using S-​approaches, with restrictions on species, stock, space, size, sex, and season. For large, industrialized fisheries, such as those for Alaskan crabs and Atlantic blue crab, annual surveys are conducted, and a large amount of information may be available for stock assessments using complex statistical models. These assessments often use derivations of the catch-​survey methodology (Collie and Sissenwine 1983). For example, the most recent assessments for blue crab in the Chesapeake Bay (Miller et al. 2011) and in the Gulf of Mexico (GSMFC 2013) use a modified catch-​survey model that allows incorporation of multiple surveys in the estimation model and are sex specific. These assessments provide fishing and abundance-​based management reference points that can be used to establish annual catch limits. Landings are typically restrained by limitations on

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Fisheries and Aquaculture MLS, fishing season, fishing area, and effort (pots or days). Populations for which stock assessments are conducted can be evaluated based on BRPs that include F/​Fmsy (the ratio of fishing mortality, F, to the F required to achieve maximum sustained yield, MSY), B/​Bmsy (the ratio of current biomass to biomass at MSY), ABC, TAC, and other measures. Management of Alaskan (Bering Sea and Aleutian Islands) Crab Fisheries The Alaskan crab fisheries of the Bering Sea and the Aleutian Islands (BSAI) are typical of large-​ scale industrial crab fisheries and are subject to some of the most modern, progressive, and scientifically responsible management. These fisheries target snow crabs (Chionoecetes opilio), Tanner crabs (C. bairdi), red and BKCs (Paralithodes camtschaticus and P. platypus), and GKCs (Lithodes aequispinus). The BSAI fisheries are home to some of the largest crab fisheries in the world, especially for snow crabs and king crabs. The BSAI crab fisheries are managed under a federal FMP that was originated in 1989 (NPFMC 2015). The major goals are to ensure long-​term reproductive viability of stocks, maximize economic and social benefits, minimize gear conflicts, preserve habitat quality, ensure vessel safety, support fisheries research and analysis, and provide open access to the regulatory process. Although the BSAI fisheries are under federal jurisdiction, management is conducted by the Alaska Department of Fish and Game (ADFG). The US National Marine Fisheries Service (NMFS) conducts annual trawl surveys for snow and Tanner crabs and red and BKCs in the Bering Sea. Sixteen other species/​fisheries are not surveyed (including golden, scarlet, and other king crab fisheries) and are not discussed here. The survey samples approximately 400 stations spaced at intervals of 20 nautical miles (nmi) with 30-​min tows covering 2.75 km. For all crabs, sex, shell condition, and size (CL or CW) are recorded, along with chela height or length. Results are presented in a trawl survey report (Daly et al. 2015), and a stock assessment report documents TAC calculations (NPFMC 2015). Management measures fall into three categories: (1) fixed in the FMP (e.g., gear restrictions, permit requirements, limited access, observer requirements, and habitat protection); (2) frameworked or flexible (e.g., MLS, harvest levels, fishing districts, seasons, closed areas, pot limits, etc.); and (3) unspecified (i.e., at state discretion, e.g., requirements for reporting, gear storage or modifications, inspections, and bycatch limits). The Alaska Board of Fisheries reviews regulatory measures seasonally, and the ADFG executes and enforces them. Management measures specified by the FMP include gear restrictions (pots), mesh sizes, escape rings, and pot limits, based on vessel size. Access is limited to a fixed number of vessels, which require permits to fish in a specific district. MLSs are established for all landed species but are adjustable. A TAC is calculated annually based on survey data. Fishing seasons are defined to minimize mortality during molting and reproductive periods and to minimize bycatch or gear conflicts. State or federal observers must be allowed aboard as required. For most Alaskan species, only males may be retained, and all females, sublegal males, or nontarget crab species must be discarded. A major pillar of the FMP is the requirement for reporting all catches, including information on the vessel, owner, gear used, effort, weight and number of crabs landed, dead loss, dates, and location of capture. All such information is confidential but usable for analysis without association to specific vessels. The NPFMC has developed a five-​tier system for determination of stock status that incorporates varying levels of information and uncertainty (NPFMC 2015). Overfishing levels (OFLs) are redefined annually, and the status of each stock is evaluated by comparing removals, including catch, discards, and dead loss, to the OFL. If an annual stock assessment is available (Tiers 1–​4), a stock is defined as overfished if the annual biomass estimates drop below a minimum stock size threshold (MSST). Prior to calculating fishery quotas, crab stocks are assigned to one of five tiers based on the availability and quality of information (Table 2.4), and harvest levels are determined by



Crab Fisheries Table  2.4. Five-​tier system used by  the North Pacific Fisheries Management Council to define quality of stock assessment information for Bering Sea Crab Fisheries (NPFMC 2015). Stocks in Tier 5 are those for which only historical catch data are available. Tier 4 stocks are those with Tier 5 data plus a current survey biomass estimate that can be used to generate proxy values of M and Bmsy. Tier 3 stocks have additional information on size at maturity and fecundity, and eggs-​per-​recruit relationships can be calculated. Stocks in Tier 2 have the previous information, and point estimates for F, Fmsy, B, and Bmsy can be calculated. Stocks in Tier 1 have the most information, including a known probability density function (pdf) for Fmsy. Data availability Historical catch data Current survey biomass estimate Size at maturity, fecundity, eggs per recruit Stock-​recruitment relationship known Estimated F, Fmsy, B, Bmsy Fmsy known as pdf

Tier 1 + + + + + +

Tier 2 + + + + +

Tier 3 + + +

Tier 4 + +

Tier 5 +

applying the calculated F, using a sliding scale in a range of 10–​20% of mature males. For Bering Sea snow crab, Bmsy is defined as the average SB (= mature males and females) during the period 1983–​1997 (NPFMC 2015). Before opening a fishery, a MSST (= 0.5 Bmsy) and a minimum fishable stock (0.25 Bmsy) must be exceeded, and a minimum guideline harvest level (GHL) is required. The ER for MMB ranges from 0.1 to 0.225, as determined by the fishing control rule (Fig. 2.4) and maximum ER on exploited legal crabs (>102 mm CW) is 0.58. The GHL is defined as MMB times ER. Prior to 2005, all Bering Sea (and other Alaskan) crab fisheries were prosecuted in an “Olympic” or derby system. TACs were assigned to the entire stock, and all vessels could compete for catches openly during the open season. As stock abundance of the larger RKC and snow crab fisheries declined, vessels were competing for a smaller piece of an ever-​shrinking pie. In 2006, after a decade of reduced landings, the NPFMC adopted a cooperative fishery management program called Crab Rationalization that was applied to most of the larger BSAI crab stocks (NPFMC 2015). Transferable quota shares were allocated among harvesters (vessels, owners, captains, and crew) and processors within fishing districts. Some portion of the TAC is set aside as a Community Development Quota for communities adjacent to the Bering Sea, and additional quota can be purchased if fished within the community boundaries. Cooperatives consisting of at least one processor and four harvesters can transfer or lease quota to facilitate fleet attrition. By 2008, effort had been reduced from >250 to only 77 vessels, a 62% reduction in vessel effort (Otto 2014). In 2005, during the last open Bristol Bay RKC fishery, 250 vessels landed 10,013 t of crabs in 3 days, worth USD70M, or about 40 t/​vessel, whereas in 2006, there were 89 vessels that landed 10,860 t in 93 days, or 122 t/​vessel. Similarly, the snow crab fishery was extended from 300 random locations within 10-​nmi grids (Moriyasu et al. 1998). Crab distributions are patchy and contagious, so data

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Fisheries and Aquaculture are analyzed using a kriging process, with variograms averaged over a 3-​year period, using depth as a covariate (Conan 1985). Trawl data are used to predict stock biomass and CPUE for the following season, which are highly correlated (DFO 2013). A snow crab habitat index is calculated as the proportion of available habitat covered by water temperatures between –​1 and 3°C. Over the past 30 years, habitat has decreased, and the stock has shifted significantly to the east as water temperatures warmed. Estimated biomass of commercial size (>101 mm CW) male crabs declined from a peak in the early 1980s to its lowest level in 1990, then increased to 103,000 t in 2004, before declining to about 63,000 t in 2011. Temperatures in the GSL in 2010–​2011 were the highest recorded since 1982, and habitat indexes reached peaks of 0.43 and 0.36 for males and females, respectively. A traffic light approach for management of the GSL snow crab fishery has been developed that incorporates 33 indicator variables, including abiotic, biotic, and anthropogenic factors representing fishery performance, abundance, and recruitment (Caddy et  al. 2005). Snow crab abundance has cycled over the last 30 years with a period of 10–​11 years. Such fluctuations have been attributed to female abundance, predation by cod, temperature, or cannibalism. Abundance of commercial crabs is associated with mean size, abundance of males 2 years earlier, and the areal extent of highest crab density (>1,000 crabs/​km2). Time series data show a potential stock recruitment relationship between abundance of small (34–​44 mm CW) crabs and mature females 6 years earlier but a strong negative relationship with larger crabs, possibly due to cannibalism. If density-​dependent effects are important, then it would be reasonable to increase ERs as abundance increases (Caddy et  al. 2005). A  general fishery control rule dictates decreasing ER as populations decline and closing fisheries in localized areas where catches exceed 20% softshell crab, as occurred in 1989. Blue Crab in Chesapeake Bay Until 1997, management of the blue crab (C. sapidus) in Chesapeake Bay was based on historical practice and landings data. Since 1989/​1990, a synoptic bay-​w ide survey has been conducted in winter to take advantage of the static distribution of crabs during cold months (Volstad et al. 2000, Sharov et al. 2003). Sampling is conducted with a single 1.83-​m dredge tow at 1,200 stations, in waters >1.5 m depth, within three regional strata. All crabs are measured, sexed, and categorized as age-​0, or age-​1+ based on size-​age conventions. Vessel-​and year-​specific catchability coefficients are used to estimate the absolute density of crabs caught at each station. Standard design-​based statistical approaches are used to expand station abundances to a total bay-​w ide abundance (Sharov et al. 2003) and verified by model-​based approaches ( Jensen and Miller 2005). Together, these data indicated a substantial decline in abundance from the early 1990s to the late 2000s. Multiple efforts to reduce fishing effort and season length were made without success. In 2008, an approach was adopted that included the closure of a winter dredge fishery in Virginia, which caught largely mature gravid females, limiting the season length of trap fisheries, and banning the harvest of egg-​bearing females late in the year. These efforts led to an increased abundance of females in 2009 and subsequent increase of age-​0 crabs in 2010, whereas males did not increase (Fig. 2.5). Despite these measures, a predicted strong 2011-​year class failed to appear, leading to a range of hypotheses, including increased fish predation, survey bias, and environmental conditions, but no definitive explanation is available. The management of blue crabs in Chesapeake Bay utilizes BRPs, including Bmsy and ER, derived from a sex-​specific, catch multiple survey model (Miller et al. 2011). In 2017, the blue crab stock in Chesapeake Bay was at 117% of its estimated Bmsy level, and ER was below recommended levels.



Crab Fisheries 700

Abundance (Millions)

600 500 400 300 200 100 0 1985

1990

1995

2000

2005

2010

2015

2020

Year Female 1+

Male 1+

Age-0

Fig. 2.5. Age-​and sex-​specific abundances of blue crab in the Chesapeake Bay derived from a winter dredge survey (for details of the survey, see Sharov et al. 2003). The vertical line indicates 2008 when female-​specific conservation measures were imposed in the fishery.

CHALLENGES AND FUTURE DIRECTIONS Challenges Selective Harvest Fishing exerts strong selection on phenotypic traits of targeted crabs, which can have direct impacts on mating systems and subsequent reproductive success. In Alaska, it was initially assumed that snow and Tanner crabs (Chionoecetes spp.) would continue to molt after maturity, so the MLS included many crabs that are morphometrically immature (adolescents). Removal of significant portions (>20%) of mature male snow crabs enforces selection against large males, promoting mating by less fecund males with smaller females, increasing sperm competition (Sainte-​Marie et al. 2008). Preference for new-​shelled snow crabs by the largest market segment ( Japan) produces a price premium for those crabs, which are typically >90% of landings. Because of terminal molt and domination of mating by old-​shell crabs, this effectively enforces greatest removals on a segment of the population, including males that have not yet mated, and the most effective maters and leaves behind adolescent and old-​shell males that are less fecund. There is evidence that male crabs subject to intensive fisheries have depleted sperm reserves (Pardo et al. 2015), and that females in fished populations have lower fecundity (Sainte-​Marie et al. 2008). Size at maturity is a result of genetic, environmental, and social influences and may also be affected by mating opportunities; however, the effects of fishing-​induced changes in competition and sexual selection on maturity size cannot be predicted due to the highly dynamic nature of populations

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Fisheries and Aquaculture and mating types and the impact of female mate choice. In addition to these short-​term effects, selection against larger animals may have long-​term genetic impacts, as demonstrated in fish populations (Conover and Munch 2002). In the Bering Sea snow crab fishery, the TAC is applied to the entire stock of Bering Sea snow crab, instead of being prorated among specific regions based on crab density or sex ratios. However, most of the catch is taken from a relatively restricted area that can change annually. Similar concerns about selective harvest in Chesapeake Bay were expressed by Jivoff et  al. (2007), who highlighted biases in the OSR of blue crab. These concerns increased with the implementation of female-​specific conservation measures in 2014 (Ogburn and Habegger 2015). Miller et al. (2011) reported changes in the sex ratio of exploitation in their assessment results, but Rains et al. (2018) demonstrated that the fishery was not capable of inducing a sufficient bias in OSR to be of concern at the population scale. Many detrimental aspects of crab fishery management might be alleviated by incorporating tenets of systemic management (Fowler 1999) and balanced exploitation (Zhou et al. 2010). At present, we know of no crab fisheries that have specifically implemented such features. Climate Impacts Climate change will have several impacts on crab fisheries. An increase of 1°C in the GSL could shift snow crab reproduction from biennial to annual, thus doubling output. In the Bering Sea, warming of 2°C, over several decades, caused contraction of the cold pool and shifting of snow crab population centroids to the north, from which they have not recovered, possibly due to the northward flow of larvae, and expansion of cod populations controlling their southern boundary (Orensanz et al. 2004). Increasing temperatures will also lead to increased size at maturity, and greater fecundity, though this may be offset by higher mortality and habitat contraction. Alternatively, shifting to a cooler regime would significantly reduce brood number, maturity size, and fecundity, but may be offset by increased survival and habitat size. Both the GSL and Labrador stocks of snow crabs have exhibited declining recruitment associated with increasing seawater temperatures, with a lag of 7–​ 9 years, indicating that warm temperatures during early ontogeny are unfavorable for snow crabs (ICES 2015). In contrast, snow crab populations have expanded into the Barents Sea, presumably as those waters became more favorable. Although high-​latitude regions are expected to respond strongly to climate change, crabs in temperate and tropical latitudes are also expected to be impacted. For example, the distribution of the blue crab is expanding northward ( Johnson 2015), and harvests in Long Island Sound, New York, are substantially higher than previously. Overwintering behavior of blue crabs in Chesapeake Bay is sensitive to climate change, with substantial impacts likely for the ecosystem and the temporal pattern in the fishery (Glandon et al. 2019). In view of the expected (and unexpected) future changes in ocean climate, maintaining diversity of size structure and high reproductive potential is critical for facilitating resilience of crab populations to climate change. Bycatch Bycatch, discard mortality, and ghost fishing are major issues for crab fisheries (Stevens 1996). Reported values are generally small, but create a negative public image. The greatest discarding of crabs occurs in nondirected (finfish) fisheries. For example, in 2005, about 290 t of RKC and about 1,750 t of snow and Tanner crabs were discarded in fisheries that collectively landed about 1.9 M t of fish (Stevens 2014). However, many crabs are also discarded during directed fisheries. In 2010 Bering Sea fisheries, 1.37 RKC were discarded for each crab retained, whereas the discard ratio for



Crab Fisheries

snow crabs was 0.23. Mortality caused by unseen gear interactions and handling is extremely difficult to assess (Stevens 2014), but preliminary estimates of posthandling mortality for snow crabs are about 30% across all size and shell conditions (ICES 2015). Bycatch of snow crabs caught in trawl fisheries, although usually 1,000,000 edwardsii Slipper Lobsters Thenus 5,000–​53,000 orientalis Ibacus sp. 1,700–​61,000 Scyllarides 100,000–​356,000 latus

Egg Embryonic Planktonic larvae Postlarvae Female age Female size Adult social Sources size development at maturity at maturity aggregations (mm) time (months) Number Duration Number Duration (years) (mm CL) of instars (weeks) of instars (weeks) 1.3

11

3

1.3–​5.1

1

2–​8

5–​8

70–​90

No

Factor (1995), Lebris et al. (2017) Powell and Eriksson (2013), Eriksson (pers. comm.) Wahle et al. (2012), Heasman and McCarthy (pers. comm.)

2.0

6–​10

3

4–​5

1

3

4–​4.5

20–​30

No

3.2

7.5

2

1

1

2–​8

3–​4

30–​40

No

0.5

1

11

26–​52

4

2–​3

2

80–​90

Yes

Phillips et al. (2013)

0.4

3

11

63–​77

4

2–​3

6–​7

56–​86

Yes

Phillips et al. (2013)

0.5

4

11

52–​104

4

2–​3

4–​6

60–​120

Yes

Phillips et al. (2013)

1.1

1.3

4

3–​6

NA

1

1

80

No

Lavalli and Spanier (2007)

1.0 0.7

2–​4 NA

7–​8 6

7–​11 NA

NA NA

NA NA

NA NA

56–​80 120

NA Yes

Lavalli and Spanier (2007) Lavalli and Spanier (2007)



Lobster Fisheries

spp. and N. norvegicus, have three posthatch larval stages followed by a metamorphosis to a postlarval stage resembling the adult. All four stages are planktotrophic, with postlarvae settling to the seabed before molting to the first benthic instar. Posthatch larval duration to settlement is generally shorter than that of spiny lobsters, spanning a few days in deep-​water species (e.g., Metanephrops spp.) to several weeks in shallow-​water species (e.g., Homarus spp. and N. norvegicus). Various species of Metanephrops found in deep continental slope waters have reduced larval stages, but still undergo metamorphosis to the postlarval stage before settlement, as in the shallow-​water forms. The most obvious distinguishing trait of clawed lobsters is their solitary existence and aggressive behavior toward conspecifics (M.P. Johnson et al. 2013, Oppenheim and Wahle 2013). Benthic juvenile clawed lobsters forage nocturnally (Lawton and Lavalli 1995, Phillips 2013, Wahle et al. 2013a), and movements beyond shelter are linked to the light-​dark cycle and size-​specific predation risk (M.P. Johnson et al. 2013). Seasonal inshore-​offshore movements are characteristic of Homarus spp. and are tied to the temperature cycle. Nephrops norvegicus, however, is not migratory but occupies galleries of burrows and tunnels in cohesive muds with which it remains associated throughout the year. While tagging studies report H.  americanus undertakes movements of hundreds of kilometers, most stay within tens of kilometers of their initial settlement location (Lawton and Lavalli 1995). No such long-​ distance movements have been reported for H. gammarus (Smith et al. 2001, Moland et al. 2011). Spiny Lobsters The reproductive biology and life history stages of the Palinuridae were extensively reviewed by Phillips (2013). In spiny lobsters, both spermatophore attachment and egg fertilization are external. Sperm storage varies with species, ranging from just a few hours as in J.  edwardsii to up to four months as in P. interruptus. Broadly, eggs of the Palinuridae are smaller and more numerous than those of the clawed lobsters. In the temperate J. edwardsii, a single egg batch is typically produced, but tropical species such as P. argus and P. cygnus may have multiple broods per year and may even breed year-​round, as in P. longipes. Embryogenesis lasts for one to four months (Phillips et al. 2013). The Palinuridae are distinguished by extended larval periods, with phyllosoma estimated to spend between four (as in P. ornatus) and 24 months (as in J. edwardsii) in the plankton. Up to 11 larval stages have been identified (Kittaka 2000), with larvae dispersing hundreds of kilometers from known breeding areas (Booth 1997, Jeffs et al. 2001). After inshore settlement of the puerulus postlarval stage, early juveniles (