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The Proceedings of the 4Th Linefish Symposium Colin Attwood, Tony Booth, Sven Kerwath, Bruce Mann, Sean Marr, Jorisna Bonthuys, John Duncan and Warren Potts (Editors)

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The Proceedings of the 4Th Linefish Symposium Colin Attwood, Tony Booth, Sven Kerwath, Bruce Mann, Sean Marr, Jorisna Bonthuys, John Duncan and Warren Potts (Editors) © WWF-SA/Peter Chadwick A DECADE AFTER THE EMERGENCY: THE PROCEEDINGS OF THE 4TH LINEFISH SYMPOSIUM Colin Attwood, Tony Booth, Sven Kerwath, Bruce Mann, Sean Marr, Jorisna Bonthuys, John Duncan and Warren Potts (Editors) Marine Technical report title: WWF South Africa Report Series - 2013/Marine/001 Acknowledgements: This work would not have been possible without the generous contributions of a scientists. These contributions are acknowledged within the various papers. Key Funders: Charl van Der Merwe Trust Two Oceans Aquarium Key Partners: Department of Agriculture, Forestry and Fisheries (DAFF) University of Cape Town (UCT) Citation: Attwood C, Booth T, Kerwath S, Mann B, Marr S, Duncan J, Bonthuys J & Potts W. (eds) 2013. A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium. WWF South Africa Report Series - 2013/ Marine/001 Published in December 2013 by WWF-World Wide Fund For Nature (Formerly World Wildlife Fund), Cape Town, South Africa. Any reproduction in full or in part must mention the title and credit the above-mentioned publisher as the copyright owner. © Text 2013 WWF-SA All rights reserved WWF is one of the world’s largest and most experienced independent conservation organizations, with over five million supporters and a global Network active in more than 100 countries. WWF’s mission is to stop the degradation of the planet’s natural environment and to build a future in which humans live in harmony with nature, by: conserving the world’s biological diversity, ensuring that the use of renewable natural resources is sustainable, and promoting the reduction of pollution and wasteful consumption. www.wwf.org.za page 2 | A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium Held at Geelbek, West Coast National Park, Langebaan 16th to 20th April 2012 Edited by Colin Attwood (Marine Research Institute, University of Cape Town) Tony Booth (Department of Icthyology & Fisheries Science, Rhodes University) Sven Kerwath ( Department of Agriculture, Forestry & Fisheries) Bruce Mann (Oceanographic Research Institute) Sean Marr (Biological Sciences Department, University of Cape Town) Warren Potts (Department of Icthyology & Fisheries Science, Rhodes University) Jorisna Bonthuys (WWF-SA) John Duncan (WWF-SA) A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium | page 3 Executive Summary The fourth Marine Linefish Symposium held at Geelbek in the West Coast National Park, from the 16th to the 20th April 2012, was attended by 71 delegates representing a variety of academic institutions and government agencies. Linefish symposia have been held approximately every decade, hosted by the National Marine Linefish Research Group, a productive and ever-changing group of fishery scientists who work on species caught by the linefishery. This symposium broke with the tradition, by not inviting fishing and industry representatives, and not inviting papers from managers. For reasons related to the number of emerging scientists and the disharmony emanating from rights allocation issues, it was deemed preferable to focus solely on science. Nevertheless, of the 36 contributed papers (including four poster presentations), not one failed to address an important management problem. The linefishery is a collective term for a variety of unrelated fish species, united only by their representation in the catches of linefishers, which themselves form a diverse group. Many such fishes are also targets of other fisheries, but the linefishery retains the Pariah status among fisheries in South Africa. Any discourse on linefish almost certainly alludes to over-exploitation, poor control and socio-economic hardships, yet this is South Africa’s oldest commercial fishery still in existence. Two likely reasons include (i) the diversity and low productivity of fishes, which has failed to attract sufficient funds for the management of any one species, and (ii) the low information content of CPUE data, which troubles conventional assessment approaches. The linefishery is in a rebuilding phase, following the legal emergency declared in 2000, and one of the most important themes of the symposium was an assessment of the effects of the regulations which followed. A renewed focus on assessment resulted in a number of important contributions, some of which, for the first time, have shown a recovery of some linefish species, and an arrest of a century-long downward spiral. Technological advances, and particularly the use of telemetry to study fish behaviour, resulted in another batch of contributions, which were as facinating as they were relevant to management. Never before have we got to know fish at such a personal level, nor can we easily comprehend their amazing journeys. Other contributions were based on genetic studies, examing stock structure and origins, trade- dynamics, user conflict and social research. Oral presentation are reproduced here in non-peer- reviewed papers, mostly condensed to 4000 words. The symposium itself produced lively discussions and a healthy (and often frank) exchange of opinions. Proceedings were wrapped up by summaries from Dr Kim Prochazka and Mr Dennis Fredericks, both of the Department of Agriculture, Forestry and Fisheries, who praised the standard of the research but also made no attempt to hide the socio-economic challenges that have yet to be addressed. Much gratitude is owed to the WWF and the Two Oceans Aquarium who funded the symposium, and to WWF who funded the publication. page 4 | A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium Foreword by Rob Tarr Scientific Manager, Fisheries Branch, Department of Agriculture, Forestry and Fisheries (DAFF) With a coastline of over 3000 kilometres, a sunny climate, and two oceans supporting a vast array of marine species, it is no surprise that the South African Linefishery is both highly active and highly productive. This productivity was recognised early, dating back to the mid- 1600s from early Dutch colonists. Already, by the mid 1800s, there was an active boat-based linefishery. Yet, despite the productivity of our oceans, history has shown that the linefish resource was not able to match the high off-take from the many users, be they commercial, recreational or subsistence. As a result, and after sustained pressure from the research community who provided evidence of stock collapse and unsustainable harvests, an emergency was declared in 2000 by the then Minister of Environmental Affairs and Tourism, and the recreational linefishing regulations were revised in 2001. The South African Linefishery is now facing severe challenges from new sectors. An expanding “Interim Relief” group that has been in existence for seven years, offers challenges in terms of increased effort, as well as the difficulty of data gathering and compliance. In addition the government’s new policy on Small Scale Fisheries is generating great interest among prospective linefishers, who are hoping for new access rights, which in terms of the policy, will be community based. It is therefore imperative that there be a solid base of scientific evidence from which to derive the advice that will be required to ensure that the threatened linefish resource is not further weakened by unsustainable expansion of fisher effort. In that regard, the content of this publication is welcomed, and timely. The purpose and theme of this Symposium, which was held in April 2012 at Geelbek, Langebaan, was to assess the effect of the major reductions in fishing effort that were imposed on the linefishery after the declaration of an Emergency, and contributions were invited that would report on this. As a result, we now have numerous papers covering the challenging area of stock assessment, as well as many others reporting on movement and genetic studies. This is an important aspect of resource management given the need to understand both stock delineation as well as the potential benefits of marine protected areas. The important area of socio-economic research is also reported on here, and this generated welcome and lively debate among the contributors to the symposium. The equally important areas of fish biology as well as some long-term monitoring studies are also reported on. I am sure that the contents of this publication will provide a solid foundation for future advice to our fishery managers. And we hope, therefore, that this fishery might continue for many more centuries, to provide recreational, subsistence and commercial benefits to the people of South Africa. A Decade After the Emergency: The Proceedings of the 4th Linefish Symposium | page 5 Table of Contents PROCEEDINGS OF THE LINEFISH SYMPOSIUM 3 EXECUTIVE SUMMARY 4 FOREWORD 5 BACKGROUND TO THE THEME: A DECADE AFTER THE EMERGENCY 9 SESSION 1 - FISH STOCK ASSESMENT: CHAIR TONY BOOTH 15 The National Marine Linefish System: The largest geo-referenced marine dataset in the world 15 Model-based standardization of multispecies catch and effort data from the South African linefishery 22 Session 2 – FISH BIOLOGY STUDIES: CHAIR BRUCE MANN 35 The biology and fisheries of king mackerel (Scomberomorus commerson) in the south west Indian Ocean 35 The effects of barotrauma on five South African line caught fishes 44 Preliminary results of the life history of red stumpnose (Chrysoblephus gibbiceps) an endemic seabream. 56 Preliminary findings on the reproductive characteristics of yellowtail (Seriola lalandi)
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