Captures of swordfish Xiphias gladius Linnaeus 1758 and loggerhead sea turtles Caretta caretta (Linnaeus 1758) associated with different bait combinations in the Western Mediterranean surface longline fishery

摘要

Fisheries worldwide use longline surface driftnets mainly for targeting swordfish Xiphias gladius Linnaeus, 1758, billfishes and sharks. Sea turtles Caretta caretta can be incidentally captured in these surface longlines, considered to be one of the most dangerous types of fishing gear for sea turtles (Cami?as et al., 2006; Lewison and Crowder, 2007). Thus, there is increasing global interest in strategies to reduce their fishery-related incidental catch. Several experiment-based studies focused on the differences associated with the use of fish and squid as bait (e.g. Watson et al., 2005; Gilman et al., 2006, 2007; Rueda et al., 2006), and recommended the use of fish-only bait rather than a squid/fish bait combination in order to reduce loggerhead turtle by-catch. In some cases implementation of these recommendations has reduced fishery income (e.g. Ariz et al., 2005), but not in other studies (e.g. Gilman et al., 2007). Fishing with longline surface driftnets is an important income source for many local Spanish economies in the Mediterranean region (de la Serna et al., 2004), and the assessment of economic profit vs conservation plans should be incorporated into the fishery analysis.