Possibility to Modify Shrimp Trammel Net to Reduce Discard Species

Abstract

The study on shrimp trammel net in cooperation with a fisherman at Warnnapasup Beach, Chonburi Province was undertaken during Oct 2004-Sep 2005. A total of 11 fishing operations was conducted to observe the fishing method, catch composition, discard problem, catch characteristic and net position of caught species in order propose an application for the modified methods to reduce discard species by this fishing gear. Shrimp trammel net is a kind of gillnet operated by sweeping the bottom net on seafloor with tidal current force. From the fishing operations, shrimps were target species and caught only about 10 % by number while 90 % was non-target species and almost all of them were discarded including economically important species. The majority of caught species were obtained by entangling and pocketing function around the bottom net panel. Increasing the mesh size of inner net and decreasing the net height are possible methods to modify the net to reduce those non-target species while least affect on shrimp catch efficiency. However, the modifications may affect the net operation especially on the net sweeping. So how big of mesh size should be increased, how tall of the net should be decreased and the affects of modified fishing gear should be considered and studied before promoting to the fishers.