Shark Depredation and Unwanted Bycatch in ... - ProDelphinus

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Shark Depredation and Bycatch in Pelagic Longline Fisheries Page vi A8.11.7. Reducing shark retention by avoiding a specific size or type of hook, or by not using wire leaders on branch lines A8.11.8. Will the economic impact of sharks be reduced from using a wire leader on branch lines A8.11.9. What is the most important factor that affects shark CPUE - altering fishing position in relation to certain water temperature, topographic features, or oceanographic features; changing the time of day or month of setting or hauling; changing the depth of hooks, or a combination of these factors? A8.12. Incentives and Attitudes on Reducing Shark Bycatch and Depredation A8.13. References Appendix 9. U.S.A. Atlantic, Gulf of Mexico and Caribbean Longline Swordfish and Tuna ... 180 Fisheries A9.1. Introduction A9.1.1. Caveats in available data sets and reports A9.1.2. Geographic fishing zones and status of the fleet A9.1.3. Gear types A9.1.4. Management parameters A9.1.5. Shark management A9.2. Incidental Shark Takes in the Atlantic A9.2.1. General takes according to species A9.2.2. Takes according to region and alternative factors A9.2.3. Shark depredation A9.3. Potential Strategies to Reduce Shark Interactions and Mortality A9.3.1. That related to other taxa or fisheries A9.3.2. That related to pelagic operations A9.3.3. Effects of J-style versus circle hooks A9.3.4. Ongoing work on hook repellants A9.3.5. Next steps A9.4. References Appendix 10. Contributing Authors’ Contact Details………………………………………………. 203
Page vii Shark Depredation and Bycatch in Pelagic Longline Fisheries Summary and Conclusions Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure shark fishing mortality levels are sustainable. In some pelagic longline fisheries, shark interactions pose substantial economic, ecological and social problems. Information on existing fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers wanting to reduce shark interactions. Improving the understanding of current and projected future longline industry attitudes and practices towards shark interactions will provide industry and management authorities with better information to manage these problems. This project collected information from a diverse range of pelagic longline fisheries in eight countries (Australia, Chile, Fiji, Italy, Japan, Peru, South Africa, and U.S.A.) to: (i) Describe the range of attitudes by the longline industry towards shark interactions; (ii) Identify methods to reduce shark depredation (the partial or complete removal of hooked fish and bait from fishing gear) and unwanted bycatch currently in practice; and (iii) Identify promising new concepts for shark avoidance and obstacles that must be overcome for their implementation. Information was collected through interviews with 149 vessel captains, fishing masters, crew, vessel and company owners, fishing cooperative staff and port officials at 24 fishing seaports for 12 pelagic longline fisheries from these eight countries, reviewing available information from the literature, and analyzing observer and logbook data. The scope of fisheries ranged from small-scale domestic artisanal fisheries to modern mechanized industrial fleets of distant water fishing nations. In some non-shark pelagic longline fisheries, sharks comprise a large proportion of the total catch. For instance, sharks comprise > 25% of the total catch in the Australia longline tuna and billfish fishery and Fiji longline tuna fishery. Sharks comprised 50% of the catch of the Hawaii-based longline swordfish fishery prior to a prohibition on the use of squid for bait, where sharks now comprise 32% of the catch. Blue sharks comprise the largest proportion of shark species caught in all 12 of the fisheries included in this study, ranging from 47% - 92% of shark catch in fisheries where this information is available. For fisheries where shark catch rates are available, these range from 0.7 to 17 sharks per 1000 hooks. The location of fishing grounds and characteristics of fishing gear and methods are primary factors determining a fleet’s shark catch rate. Certain gear designs (e.g., use of a wire leader, use of squid for bait, and depth of baited hooks) contribute to high shark catch rates. Shallow setting pelagic longline fisheries generally have higher shark catch rates than deeper setting fisheries. Gear designs are extremely variable between fisheries, as well as from seaport to seaport, by season and fishing ground within a fishery, between vessels within a fishery, and for some parameters, within the gear of an individual vessel.
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Shark Depredation and Bycatch in Pe
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