A trouser bag experiment that quantify by-catch species escaping from a modified shrimp beam trawl codend with excluder device

Abstract

Sea fishing trials were conducted to quantify by-catch species escaping from a modified shrimp trawl codend and retained in a trouser bag. Modification was by inserting a rectangular aluminum frame excluder device with bar spacing of 20mm at the anterior bunt. Thirty replicate landings showed that; Drepane africana have the highest escape rate of SO.76% followed by Pseudotolithus elongatus (46.83%), while flat fishes like Dasyatis margarita and shell fishes like Callinectes amnicola have low escape rates of zero and 17.62%  respectively. Among the five fish groups of pelagic, semi-pelagic, demersal, shell and target shrimps, pelagic have the highest escape rate of 39.8% and target shrimps Nematopolaemon hastatus the least, 2.3%. The influence of water flow speed in the cod end on t he escape rates of five fish groupings is discussed.

Key words: Trouser bag, by-catch, Codend, Excluder device.