Fisheries Bycatch of Sharks: Options for Mitigation

Cosandey-Godin A, Morgan A (2011) Fisheries Bycatch of Sharks: Options for Mitigation. Pew Environmental Group, Washington DC

Bycatch is one of the most significant issues in the management and conservation of global fisheries (Hall et al. 2000, Kelleher 2005, Lewison et al. 2004) and has been identified as one of the leading causes of shark population declines. Sharks are susceptible to high fishing mortality rates because of their life history characteristics, which include slow growth, late ages at maturity, and the production of a limited number of young over a lifetime (Cortes 2002, Heppell et al. 1999, Cortes 1999). In addition, research has shown that several species of sharks have very high rates of mortality associated with the fishing process (Morgan and Burgess 2007, Mandelman et al. 2008), and it has been estimated that species such as sandbar shark (Carcharhinus plumbeus) (Sminkey and Musick 1994, Cortes 1999) and dusky shark (Carcharhinus obscurus) (Simpfendorfer 1999) increase their population sizes so slowly that they are considered particularly vulnerable to mortality from fishing activities (Musick et al. 2000a). For example, Cortes et al. (2006) found that if fishing for dusky shark stopped for 30 years, their population in the Northwest Atlantic would still be depleted.

Over the past two decades, serious population declines have been reported for a number of shark species in several regions around the world (Baum et al. 2003, Ferretti et al. 2008, Robbins et al. 2006, Ferretti et al. 2010, Clarke 2011) and are attributed to both targeted and incidental capture. According to the International Union for Conservation of Nature (IUCN) and other sources, bycatch is one of the primary threats facing sharks (Musick et al. 2000b, Lewison et al. 2004).

Despite widespread recognition of shark bycatch issues (Food and Agriculture Organization [FAO] 1999; FAO 2010), few mitigation actions have been established, and there are no clear guidelines about which mitigation actions would be most effective. In addition, there are very few management measures requiring actions to mitigate shark bycatch. However, it is clear that managers and fishermen must aim to reduce both bycatch rates and the harmful effects from bycatch (e.g., injuries from capture on fishing gear).

Based on the best available information, this review provides a summary of the current knowledge and understanding of shark bycatch and discusses available management options and technical measures aimed at reducing both the rate at which sharks encounter fishing gear and the associated damaging effects.