Size-Selectivity of Trammel Nets for Two Herbivorous Fish Species in Coral Reef Fisheries of Jeddah, Saudi Arabia

摘要

Acanthurus sohal and Siganus rivulatus in Jeddah fisheries was investigated using three different inner-panel mesh sizes: 50, 56, and 62 mm. The SELECT method was used to calculate selectivity parameters. Five models were fitted to estimate the selectivity curves, namely: normal location, normal scale, lognormal, gamma and bi-modal. In addition, lengthgirth (G_max) and length-weight relationships were determined. Based on the lowest deviance/degrees of freedom ratio, the lognormal model provided the best fit for S. rivulatus catch, with modal lengths of 18.3, 20.5, and 22.7 cm, whereas the bi-modal model provided the best fit for A. sohal catch, with modal lengths of 19.30, 21.62, and 23.93 cm for 50, 56 and 62 mm mesh sizes, respectively. The length-girth relationship could be described by the linear equation: G_max = 0.69+0.67xTL for S. rivulatus and G_max=1.32+0.712xTL for A. sohal. The length-weight relationship could be described by the power equation: W=0.024xTL^2.81 for A. sohal and W=0.015xTL^2.99 for S. rivulatus. We recommend using trammel nets with a minimum inner-panel mesh size of 62 mm for the rational exploitation of the two species.