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Elasmobranchs (Sharks and Rays): a Review of Status, Distribution and Interaction with Fisheries in the Southwest Indian Ocean

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Elasmobranchs (Sharks and Rays): a Review of Status, Distribution and Interaction with Fisheries in the Southwest Indian Ocean See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/277329893 Elasmobranchs (sharks and rays): a review of status, distribution and interaction with fisheries in the Southwest Indian Ocean CHAPTER · JANUARY 2015 READS 81 2 AUTHORS, INCLUDING: Jeremy J Kiszka Florida International University 52 PUBLICATIONS 389 CITATIONS SEE PROFILE Available from: Jeremy J Kiszka Retrieved on: 16 October 2015 OFFSHORE FISHERIES OF THE SOUTHWEST INDIAN OCEAN: their status and the impact on vulnerable species OCEANOGRAPHIC RESEARCH INSTITUTE Special Publication No. 10 Rudy van der Elst and Bernadine Everett (editors) The Investigational Report series of the Oceanographic Research Institute presents the detailed results of marine biological research. Reports have appeared at irregular intervals since 1961. All manuscripts are submitted for peer review. The Special Publication series of the Oceanographic Research Institute reports on expeditions, surveys and workshops, or provides bibliographic and technical information. The series appears at irregular intervals. The Bulletin series of the South African Association for Marine Biological Research is of general interest and reviews the research and curatorial activities of the Oceanographic Research Institute, uShaka Sea World and the Sea World Education Centre. It is published annually. These series are available in exchange for relevant publications of other scientific institutions anywhere in the world. All correspondence in this regard should be directed to: The Librarian Oceanographic Research Institute PO Box 10712 Marine Parade 4056 Durban, South Africa OFFSHORE FISHERIES OF THE SOUTHWEST INDIAN OCEAN: their status and the impact on vulnerable species Rudy van der Elst and Bernadine Everett (editors) South African Association for Marine Biological Research Oceanographic Research Institute Special Publication No. 10 May 2015 Book title: Offshore fisheries of the Southwest Indian Ocean: their status and the impact on vulnerable species Editors: Rudy van der Elst and Bernadine Everett First published in Durban in 2015 by the Oceanographic Research Institute (ORI) and the Western Indian Ocean Marine Sciences Association (WIOMSA) Copyright © 2015 | ORI and WIOMSA ISBN: 978-0-620-64762-5 (digital); 978-0-620-64761-8 (print) Copyright notice: All rights of this publication are reserved to ORI, WIOMSA, the editors and the authors of individual chapters. Notwithstanding, this publication may be reproduced in whole or in part for educational or non-profit purposes without special permission from the copyright holders provided that acknowledgement of the source is made. No use of this publication may be made for resale or any other commercial purpose without permission in writing from the copy- right holders. Disclaimer: the contents of this publication do not necessarily reflect the views of ORI, WIOMSA, Sida or the GEF. Fur- thermore, the geographic designations used in this publication do not imply any opinion as to the legal status or delinea- tion of any territory referred to. Acknowledgement: This book is based on research by the Southwest Indian Ocean Fisheries Project (SWIOFP) and its publication has been made possible by the generous support of the Government of Sweden and the Global Environmental Facility (GEF) through the Western Indian Ocean Marine Science Association. Book citation: Van der Elst RP and Everett BI. 2015. (eds). Offshore fisheries of the Southwest Indian Ocean: their status and the impact on vulnerable species. Oceanographic Research Institute, Special Publication, 10. 448pp. Design: Desiré Pelser | Earth & Oceans Developments | Publications and Communications NM IRO EN V T N F E A L C A I B L I O T L Y G I N T V E E N ST L A I N P G I N O U R GEF.org 11. ELASMOBRANCHS (SHARKS AND RAYS) 366 | OFFSHORE FISHERIES OF THE SOUTHWEST INDIAN OCEAN Table of contents A bstract . 367 Introduction . 367 Regional biodiversity and critical habitats for elasmobranchs in the Southwest Indian Ocean (SWIO) . 368 Country overviews . 368 South Africa (KwaZulu-Natal) . 368 Mozambique . 369 Tanzania . 370 Kenya . 370 Union of the Comoros . 370 Mayotte (including Iris, Zélée and Geyser banks) . 370 French dispersed islands (Europa, Bassas da India, Juan de Nova, Glorieuses, and Tromelin) . 370 Madagascar . 371 Seychelles . 371 La Réunion . 371 Mauritius . 371 Sharks of the open ocean in the SWIO: overview of biodiversity . 372 Migratory routes and population structure of elasmobranchs . 373 Relationship with fisheries . 374 Coastal fisheries that take elasmobranchs in SWIO countries . 374 South Africa (East Coast region) . 374 Mozambique . 375 Tanzania . 376 Kenya . 376 Union of the Comoros . 376 Mayotte and French dispersed islands (Europa, Bassas da India, Juan de Nova, Glorieuses, Tromelin) . 377 Madagascar . 377 Seychelles . 378 La Réunion . 378 Mauritius . 378 Overview of open-ocean shark bycatch in the WIO . 379 Management of shark fisheries and mitigation of bycatch in the SWIO . 380 Coastal fisheries . 380 Oceanic fisheries . 380 Gaps and recommendations . 381 Literature cited . 382 Annex . 386 Previous page: Silky shark, C. falciformis . One of the most common bycatch shark species in the open-ocean purse seine fishery associated with floating objects . Photo by Chris Fallows, www .apexpredators .com . ELASMOBRANCHS (SHARKS AND RAYS) | 367 11. ELASMOBRANCHS (SHARKS AND RAYS) A review of status, distribution and interaction with fisheries in the Southwest Indian Ocean Jeremy Kiszka1 and Rudy van der Elst2 Abstract A n overview of available information on sharks and rays in the Southwest Indian Ocean (SWIO) is presented, highlight- ing their dynamics, role in fisheries and conservation status . Despite their prominence , little directed research and assessment has been undertaken with the exception of studies in KwaZulu-Natal (South Africa), largely attributable to historic problems of shark attack . Additional drivers of research have focussed on charismatic species with tourist value . Elasmobranchs are targeted or taken as bycatch in a range of SWIO fisheries, including longline, purse seine, pelagic drift net and especially shrimp trawling with high impact on endemic species . Some 188 species have been recorded by 39 nations totalling a catch of > 100,000t in 2012 . However, FAO records reveal that shark catches in the western Indian Ocean have almost halved from a peak of 180,000t in 1996 . Analysis of records for coastal waters of 11 SWIO countries provides insight into the scale of fisheries and conserva- tion status of elasmobranchs in different regions . Available information on shark behaviour, ecology, local distribution, aggregations, nursery areas and migrations is interrogated . Significant information gaps remain with knowledge on the ecology, biology and fisheries for elasmobranchs highly fragmented; disconcerting in the light of declining catches in the SWIO . Available data is generally inadequate for the assessment and management of stocks . However, new smart tag technology and genetic profiling is expanding the information on elasmobranchs . In addition, some mitigation measures have been implemented to minimise elasmobranch bycatch through the installation of bycatch reduction devices (BRDs) in several trawl fisheries . A start has also been made with the FAO-promoted National Plans Of Action for sharks (NPOA), with several countries having produced initial reports to underpin the conservation and management of sharks . Introduction stable environment, and generally have limited capacity to Elasmobranchii is one of the two subclasses of cartilaginous sustain and recover from heavy fishing pressure. fish in the class Chondrichthyes, the other being Holocephali Among the 1,160 species of cartilaginous fishes known, (chimaeras). They occur in all oceans, from coastal to ocean- 188 have been recorded in the Southwest Indian Ocean ic waters, from the surface to depths of more than 3,000 me- region (SWIO). Except for South Africa (especially the coast ters (Priede et al. 2006). Elasmobranchs range from plankti- of KwaZulu-Natal province), little effort has been made to vores to apex predators and exhibit every reproductive mode assess the status of sharks and rays in the SWIO, although known in vertebrates, from egg laying to placental viviparity some species have been more investigated than others in the (Shelson et al. 2008). Most elasmobranchs (sharks and rays) region, notably the larger and emblematic species such as and the related chimaeras are characterised by low fecundi- the whale shark (Rhincodon typus) and the reef manta ray ty and productivity, slow growth, late age at maturity, large (Manta alfredi). size at birth, high natural survivorship and a long life. Such This chapter provides an overview of available information biological characteristics have serious implications for the on the status, fisheries (including directed exploitation and sustainability of shark and ray fisheries (Kiszka & Heithaus incidental catches, or bycatch) and management of elasmo- 2014). Not surprisingly, these species are dependent on a branchs in the SWIO. 1 . Florida International University, School of Environment, Arts and Society (SEAS), Miami . Email: jkiszka@fiu .edu 2 . Oceanographic Research Institute, Durban . 368 | OFFSHORE FISHERIES OF THE SOUTHWEST INDIAN OCEAN Regional biodiversity and critical on elasmobranch ecology, taxonomy, distribution, and abun- habitats for elasmobranchs in the dance have been produced
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