Effects of Net Depth Reduction to Bigeye Tuna (Thunnus obesus) Catch

Analysis on the catch of Bigeye tuna (Thunnus obesus) from purse seine and ring nets of various net depths was conducted to assess the effect of reducing net depth as a compatible measure the Philippines has implemented and reducing the catch of Bigeye in its internal waters and the Exclusive Economic Zone (EEZ). The study was based on observer reports from ring net and purse seine fishing vessels operating in internal waters and EEZ as well as from group seine operations in the high seas pocket 1. Nets were classed by depth to determine and compare variations on the catch of Bigeye, catch rates and relative proportion, species composition, and fishing grounds. Results indicated that the catch of Bigeye is correlated with the depth of net, with a significantly higher catch of Bigeye in deeper nets. The result of the study is consistent with other studies elsewhere, and in consonance with the implementation of Fisheries Administrative Order 236 limiting the depth to 115 fathoms for ring net and purse seine operating in Philippine internal waters and the EEZ as a compatible measure to reduce the catch of Bigeye.