Preliminary research on stock of pelagic sharks in the Atlantic Ocean

DAI Xiao-jie~(1,2),XU Liu-xiong~1(1.Ocean College, Shanghai Fisheries University, Shanghai200090, China; 2.School of Life Sciences,East China Normal University,Shanghai200062, China)

Isurus oxyrinchus; Prionace glauca; catch per unit of effort(CPUE); yearly average biomass

Based on the data from four trips surveyed, the paper made analysis on the stock of pelagic sharks in the tropical Atlantic Ocean. Fishery data on pelagic sharks are obtained from International Commission for Conservation on Atlantic Tunas(ICCAT). Results shows that there are 13 pelagic sharks occurring in the Atlantic longline catch and dominant species are short mako(Isurus oxyrinchus) and blue shark(Prionace glauca). The shortfin mako catch per unit of effort(CPUE) of the first, second and fourth trips tend to decline, with the values of 0.3502, 0.1754 and 0.0642 per thousand hooks respectively. The blue shark catch per unit of effort(CPUE) of preceding three trips fluctuated between 5-7 per thousand hooks. The blue shark CPUE(0.8 per thousand hooks) of the fourth trip declines dramatically. The paper reported the catches of shortfin mako and blue shark caught by China tuna fleet since 1993. The paper also estimates the yearly average biomass of two dominant sharks based on the fishing mortality and catch data, and discusses affecting factors for shark CPUE and stock status.