Trawl Selectivity Estimates of Thryssa dussumieri (Valenciennes, 1848) in Square and Diamond Mesh Codends

Abstract

Codend selectivity of Thryssa dussumieri, an important trawl resource along Gujarat coast was studied using covered codend method. The selectivity estimates were worked out for 40 mm diamond and square mesh codends by staked haul method to account variation associated with multiple hauls considered for deriving the selectivity. The length at 50% retention of the species for the 40 mm diamond and square mesh codends were worked out as 8.84±0.16 and 10.20±0.12 cm respectively. The selection range, selection factor and selection ratio for the diamond mesh codend was 7.96±0.42 cm, 2.21 and 0.9 respectively and for the 40 mm square mesh codend these values were 3.76±0.19 cm, 2.55 and 0.37 respectively. Considering the length at first maturity of the species as 125 mm, the optimum mesh size for 40 mm diamond mesh and square mesh codend were worked out as 56.6 and 49 mm respectively for conservation of the species.