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

Özet

Size-selectivity of monofilament trammel nets for two important herbivorous species. 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, length-girth (Gmax) and length-weight relationships were determined. Based on the lowest deviance/degrees of freedom ratio, the log-normal 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: Gmax = 0.69+0.67TL for S. rivulatus and Gmax=1.32+0.712TL for A. sohal. The length-weight relationship could be described by the power equation: W=0.024TL2.81 for A. sohal and W=0.015TL2.99 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. two species. Materials and Methods