Shark-catch composition and seasonality in the data-poor small-scale fisheries of the southern Gulf of Mexico

Abstract

Regional ecological information is relevant to the international management of vulnerable species such as sharks. On the basis of monthly fishery data (2007–2010) from two small-scale multispecies fleets, namely, the bottom longline fleet (MLL) and vertical line+shark-specific longline fleet (VL+SSL) operating on the Campeche Bank, we recorded 19 shark species. The occurrence of immature stages of 15 species, gravid females of Carcharhinus leucas, three Endangered species (Sphyrna mokarran, S. lewini, Isurus oxyrinchus) and three Vulnerable and six Near-threatened species emphasises the importance of this area. Rhizoprionodon terraenovae (42.01% of total abundance), S. lewini (24.82%) and S. tiburo (14.57%) were the most abundant species. The commercial logbooks (2007–2012) for one fleet recorded 6517 for MLL and 1617 for VL+SSL fishery trips. The general additive model indicated a maximum of shark catch rate (CR) for MLL and SSL during 2011 (mean±s.e., 49.94±8.44 and 91.38±16.07kg per 100 hooks respectively). Monthly CR for MLL was highly variable; the maximum was observed in February (15.45±21.43kg per 100 hooks), the maximum monthly CR for SSL was in January (88.04±14.85kg per 100 hooks). For MLL, a positive relation was observed between effort and CR, whereas, for SSL, no clear relation was observed.