The term ‘bycatch’ is used for fish caught unintentionally in a fishery that is designated to catch other fish. Many fishing techniques and gear are not very selective and result in catching and discarding millions of tons of marine life that was not the target species, accounting for over 40% of the estimated total marine catch (Davies et al. 2009). Longline fishing, typically used to catch tuna, employs miles of fishing line with thousands of hooks that indiscriminately catches whatever comes along to eat the bait, including turtles, seabirds and sharks. In addition to longlines, gear such as bottom trawlers and gillnets also produce large numbers of shark bycatch (Bonfil 2000).
Until recently, shark ‘bycatch’ was considered a nuisance and sharks were cut loose and disposed of overboard, sometimes still alive. However, as shark fins have become increasingly valuable, these fleets have little incentive to take measures to reduce shark bycatch. It is easier and more profitable to cut off the fins and discard the bodies at sea.
The term ‘bycatch’, in reference to sharks, may be a misnomer. Despite available means to decrease bycatch of sharks, the strong economic incentive to keep the fins reduces the likelihood of implementing these methods. Simple gear changes, such as switching from steel to nylon leaders, have demonstrated a reduction of shark bycatch while improving catch of ‘target’ species (Ward et al. 2007). New hook designs, weak or smart hooks, as well as new shark derrents and fishing methods could greatly reduce shark bycatch while also resulting in higher yields of target fish, saving time and money for the crews (Gilman et al. 2008).
New methods my reduce bycatch but some may still end up on a hook. The good news is greater than 95% of the species of shark most commonly caught as bycatch can be released if fishing crews can use safe and efficient release practices and for species such as the blue shark, the most commonly caught shark as bycatch, survival rates are high when released (Moyes et al. 2006). If it wasn’t for the valuable fins, these sharks would probably not be retained!
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