Abundance and distribution of sharks in Los Roques Archipelago National Park and other Venezuelan oceanic islands, 1997–1998

Abstract

The relative abundance and distribution of sharks caught by the artisanal fishery was determined for the most important offshore islands of Venezuela (Los Roques, Las Aves and La Blanquilla). Data were collected from January 1997 to October 1998, corresponding to 123 fishing days targeting sharks using bottom longline. We also present the results of 10 days of fishing activities targeting tunas and marlins by the same fleet using pelagic longline, in order to determine the importance of the shark bycatch in these fisheries around the offshore islands. A total of 15 shark species representing five families were captured during the study period. The catch composition and CPUE values expressed in weight and number showed that the most abundant species were Carcharhinus perezi and C. falciformis for Los Roques Archipelago and La Blanquilla Island, while C. perezi and Ginglymostoma cirratum were more common in Las Aves Archipelago. In Los Roques Archipelago, C. perezi and C. falciformis were most common during the second half of the year; a similar trend was observed for the rest of the shark species caught by the fishery. A positive relationship was observed between CPUE and fishing depth in the case of C. perezi and C. falciformis off Los Roques Archipelago: CPUE by weight increases with depth, while CPUE by number decreases with depth. The main factors that could be determining shark abundance and their spatial-temporal distribution are the characteristics of the ecosystem, depth, and biological characteristics such as birth, mating season and migratory patterns of the species.