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Turkish Journal of Fisheries and Aquatic Sciences 2016, Vol 16, Num, 4     (Pages: 993-1002)

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

Mohamed Hosny Gabr 1-2 ,Ahmad Osman Mal 1

1 King Abdulaziz University, Faculty of Marine Science, Marine Biology Department, 80207, Jeddah 21589, Saudi Arabia
2 National Institute of Oceanography and Fisheries, Suez, Egypt
DOI : 10.4194/1303-2712-v16_4_26 Viewed : 1718 - Downloaded : 1274 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 (Gmax) 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: Gmax = 0.69+0.67xTL for S. rivulatus and Gmax=1.32+0.712xTL for A. sohal. The length-weight relationship could be described by the power equation: W=0.024xTL2.81 for A. sohal and W=0.015xTL2.99 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. Keywords : Siganus rivulatus, Acanthurus sohal, length-weight relationship, length-girth relationship, selectivity models