Bycatch Species Groups

    Seabirds, sea turtles, sharks and rays, and marine mammals are the four species groups that are the focus of the BMIS. These species are incidentally caught in oceanic longline and purse-seine tuna and billfish fisheries. Sharks are always treated as bycatch for the purposes of the BMIS, although they may be targeted or treated as an associated catch in some tuna fisheries.

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    Sea Turtles

    Sea turtle bycatch occurs in several ways, through hooking or entanglement on longlines, entanglement on FADs, and they are sometimes netted in in purse seines. Successful bycatch mitigation techniques include replacing squid with fish bait, using circle hooks, dynamic spatial and temporal measures (e.g. TurtleWatch), and improved FAD design.


    In pelagic longline fisheries, seabirds may become hooked and drown when they take a baited hook. Mitigation of seabird bycatch aims to deter and prevent birds from taking bait, principally through the combined use of multiple techniques, including streamer (tori) lines, fast sinking, weighted branch lines and night setting.