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Bycatch in Longline Fisheries for Tuna and Tuna-Like Species: a Global Review of Status and Mitigation Measures

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Bycatch in Longline Fisheries for Tuna and Tuna-Like Species: a Global Review of Status and Mitigation Measures Cover photographs: Courtesy of S. Clarke. Cover illustration: Courtesy of FAO. FAO FISHERIES AND BYCATCH IN LONGLINE AQUACULTURE TECHNICAL FISHERIES FOR TUNA PAPER AND TUNA-LIKE SPECIES: 588 A GLOBAL REVIEW OF STATUS AND MITIGATION MEASURES Shelley Clarke ABNJ Tuna Project Technical Coordinator-Sharks and Bycatch Western and Central Pacific Fisheries Commission Federated States of Micronesia Mayumi Sato BirdLife International Marine Programme Asia Coordinator BirdLife International Asia Division Japan Cleo Small Head BirdLife International Marine Programme The Royal Society for the Protection of Birds (RSPB) United Kingdom Ben Sullivan BirdLife International Marine Programme Coordinator The Royal Society for the Protection of Birds (RSPB) Australia Yukiko Inoue and Daisuke Ochi Scientists Ecologically Related Species Group, Tuna and Skipjack Resources Division National Research Institute of Far Seas Fisheries, Fisheries Research Agency Japan FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 2014 The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO. E-ISBN 978-92-5-108525-7 (PDF) © FAO, 2014 FAO encourages the use, reproduction and dissemination of material in this information product. Except where otherwise indicated, material may be copied, downloaded and printed for private study, research and teaching purposes, or for use in non-commercial products or services, provided that appropriate acknowledgement of FAO as the source and copyright holder is given and that FAO’s endorsement of users’ views, products or services is not implied in any way. All requests for translation and adaptation rights, and for resale and other commercial use rights should be made via www.fao.org/contact-us/licence- request or addressed to [email protected]. FAO information products are available on the FAO website (www.fao.org/ publications) and can be purchased through [email protected]. iii Preparation of this document This publication is the third in a series of FAO Fisheries and Aquaculture Technical Papers reviewing bycatch in global tuna fisheries and it deals with longline fisheries. Its scope is defined taxonomically to comprise only non-tuna and non-tuna-like species, i.e. elasmobranchs, sea turtles, seabirds, marine mammals and other (non-target) bony fishes. This document was written and edited by Dr Shelley Clarke, with the exception of Chapter 4, which was written by Drs Mayumi Sato, Cleo Small, Ben Sullivan, Yukiko Inoue and Daisuke Ochi. iv Abstract This publication is the third in a series on bycatch in global tuna fisheries. Dealing with longline fisheries, its scope is defined taxonomically to comprise only non-tuna and non-tuna-like species. The history of longline fishing illustrates the role of new technologies, the expansion of fishing grounds, and the operational characteristics of the fleets in shaping today’s fishery. More recently, management regulations, the price of oil, the cost of labour, and market demand have also exerted an influence. No more than 23 percent of the tuna in each ocean is longline-caught. However, there may be up to 7 500 tuna longliners globally with almost 60 percent of them less than 24 m in length. Available data suggest that elasmobranch catches have fallen 14 percent since their peak in 2003. In longline fisheries, shark catch rates may be determined by bait type, soak time, hook shape, leader length and material, depth at which the hook is fished, and whether special gear is deployed to target sharks. Vulnerability to hooking, and resilience to haulback and handling, vary by species, size, area and fleet operational practices. Tuna regional fisheries management organizations (t-RFMOs) assess the status of shark populations but data limitations often hinder firm conclusions. There is little information on the implementation or effectiveness of finning bans and no-retention measures. Mitigation measures have been tested but results vary. Six of the seven species of sea turtles are threatened with extinction, and while longline fisheries may have less impact than net-based fisheries, significant population- level impacts may be occurring in some regions. The greatest concern is associated with loggerhead–longline interactions in the Atlantic. Circle hooks and using finfish bait have proved effective mitigation techniques either by reducing hooking or hook swallowing. Other methods require further development. Interactions with pelagic longline fisheries kill 50 000–100 000 seabirds annually. Many of these species, particularly albatrosses, are threatened with extinction. Recent advances in tracking technologies have facilitated mapping of where interactions are most likely. The Western and Central Pacific contains more than 45 percent of the global total albatross and giant petrel breeding distributions. The most promising mitigation methods appear to be night setting, side-setting, line weighting and streamer lines, but further research is needed. All five t-RFMOs require use of one or more of these methods in areas that overlap albatross distributions. However, compliance data are limited and improved observer coverage is essential. Marine mammals’ interactions with longline fisheries are detrimental to the fishery but may be positive or negative for the mammals. Although it is often unclear which species are involved, pilot whale interactions in the western Atlantic and false killer whale interactions off Hawaii have triggered national mitigation plans. No t-RFMO has adopted management measures for marine mammal interactions. Research and testing of mitigation measures continue in order to ameliorate both marine mammal impacts and economic losses to industry from depredation. At least 650 species of other bony fishes may be caught in association with pelagic longline fisheries, e.g. dolphinfish, opah, oilfish, escolar and ocean sunfish. Some of these stocks are important as local food supplies. However, it is unclear whether these stocks or the ecosystem they help structure is at risk. More attention should focus on improving fishery statistics and initiating basic monitoring of these stocks’ status. The diversity of pelagic longline gear designs and fishing methods, the variety of habitats they are deployed in, the thousands of marine species they may interact with, v and the different mechanisms and behaviours that govern those interactions provide an array of topics to be addressed in any discussion of bycatch mitigation. Scientific and technical issues in mitigation including effects across taxa, effects of combinations of measures, economic and safety considerations, underlying biological mechanisms, handling and post-release mortality, and non-fishery impacts must all be addressed. In addition, it is also necessary to consider issues such as who takes the lead for ensuring mitigation is sufficient for the population as a whole, how to devise effective mitigation implementation strategies, and whether gear modification should be used in concert with more sweeping measures. Clarke, S., Sato, M., Small, C., Sullivan, B., Inoue, Y. & Ochi, D. 2014. Bycatch in longline fisheries for tuna and tuna-like species: a global review of status and mitigation measures. FAO Fisheries and Aquaculture Technical Paper No. 588. Rome, FAO. 199 pp. vii Contents Preparation of this document iii Abstract iv Tables x Figures xii Plates xiv Acknowledgements xv Abbreviations and acronyms xvi 1. Introduction 1 1.1 Background and definition of scope 1 1.2 Data sources and data quality issues 4 1.2.1 T-RFMO data sets relevant to longline bycatch 4 1.2.2 Other data 8 Global trends in longline fisheries 9 Catch 9 1.3.2 Effort 11 1.3.3 Value 12 1.3.4 Technological and operational changes in longline fisheries 13 1.3.5 Other factors influencing trends in longline fishing 15 2. Elasmobranchs 19 2.1 Overview of elasmobranch interactions with longline gear 19 2.1.1 Background, definitions and concepts 19 2.1.2 Factors influencing elasmobranch interactions and mortality 23 2.1.3 Species risk profiles 25 2.2 Elasmobranch interactions, mortality rates and stock status by area 29 2.2.1 Atlantic Ocean 29 2.2.2 Eastern Pacific Ocean 31 2.2.3 Western and Central Pacific Ocean 32 2.2.4 Indian Ocean 37 2.2.5 Summary of shark stock status 38 2.3 Management measures and their effectiveness 39 2.3.1 Finning controls 39 2.3.2 Catch controls 40 2.3.3 Operational and gear controls 41 2.3.4 Closures 42 2.3.5 Trade controls 43 2.3.6 National plans of action 43 2.4 Review of Mitigation Methods 43 2.4.1 Modifying fishing behaviour 44 2.4.2 Modification of fishing gear 45 2.4.3 Repellents and other deterrents 48 2.4.4 Handling practices for hooked sharks 49 2.5 Conclusions regarding elasmobranch interactions 50 viii 3. Sea turtles 53 3.1 Overview of sea turtle interactions with longline gear 53 3.1.1 Taxonomy and impact characterization 53 3.1.2 Factors influencing sea turtle interactions and mortality 54 3.1.3 Species risk profiles and international conservation initiatives 58 3.2 Sea turtle interactions by area 59 3.2.1 Atlantic 60 3.2.2 Eastern Pacific 62 3.2.3 Western and Central Pacific 63 3.2.4 Indian Ocean 66 3.3 Management measures and their effectiveness 67 3.4 Review of mitigation methods 70 3.4.1 Hook type 71 3.4.2 Bait type 73 3.4.3 Other gear and operational controls 74 3.4.4 Habitat avoidance 76 3.4.5 Deterrents 78 3.4.6 Release using line cutters / de-hookers 78 3.5 Conclusions regarding sea turtle interactions 79 4.
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