Shark depredation and unwanted bycatch in pelagic longline fisheries industry practices and attitudes, and shark avoidance strategies

Citation
Gilman E, Clarke, S., Brothers, N., et al (2007) Shark depredation and unwanted bycatch in pelagic longline fisheries industry practices and attitudes, and shark avoidance strategies. Western Pacific Regional Fishery Management Council, Honolulu, Hawaii
Abstract

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.