Catch Composition and Some Biological Aspects of Silky sharks (Carcharhinus falciformis) landed by Surrounding Net Fishery in Sri Lanka

The surrounding net (ring net) fishery in Sri Lanka is responsible for more than 36% of total large pelagic fish landings, while the highest landings are recorded from coastal fisheries (37%). This study was carried out on a monthly basis from January 2019 to December 2021 to investigate the catch composition and reproductive aspects of silky sharks (Carcharhinus falciformis) landed as by-catch in the ring net fishery in major fish landing sites in Sri Lanka. Skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacores), frigate tuna (Auxis thazard), and rainbow runner (Elagatis bipinnulata) contributed to the by-catch, while sharks contributed quite a small quantity, less than 1% in weight. 82% of the shark by-catch is composed of silky sharks, followed by blue sharks (14%) and Isurus sp (2%) A total of 1197 silky sharks were recorded during the study period, and the fork length range was 69–204 cm. The overall sex ratio for males and females was determined at 1:6. The results showed that more than 80% of the silky sharks landed by the purse seine ring net were juveniles. Recorded fishing locations were scattered, but most were confined to the Exclusive Economic Zone. The silky shark can be considered as a highly vulnerable shark species to the ring net fishery in Sri Lanka, and this study provides important information on their reproductive aspects, which will be crucial to the implementation of management and conservation measures.