Minimising Unwanted Shark Interactions and Mortalities in CCSBT Longline Fisheries

This paper provides a brief overview of techniques and strategies that can serve to minimize unwanted interactions with sharks in longline fisheries, including those fishing for southern bluefin tuna. Mitigation is a complex subject and the conclusions drawn in this or any overview paper from available studies may not be representative of performance across all fisheries. Nevertheless, in order to provide a framework for understanding the range of available options, this paper summarizes ways of modifying fishing behaviour (setting hooks deeper, reducing soak time, and fleet communication to avoid hotspots); ways of modifying fishing gear (using circle hooks, using nylon (not wire) branchlines, and using fish (not squid bait); applying repellents or deterrents (electrical or magnetic, olfactory or chemical, and artificial bait); and options for safe handling (cutting sharks free in water or removing gear from sharks). Promising options are identified although in each case it will be necessary to further consider the mitigation’s effectiveness for the fishery in questions as well as the acceptability to fishers in terms of impacts to target species catches, crew safety, operational costs and environmental effects.