Determination of a standard mesh size of gill- net for yellowfin tuna in Oman Sea ( Sistan and Baluchistan Province )

Abstract

This study examined yellowfin tuna catch data of a series of gill-net sets including 5 ¾ (Control), 6 ¾ , 7 ¾, 8 ½ and 9 1 /3 in both surface and mid-water catch method. Of the total research Cruises (22 days) done on March and April 2002, 19 and 3 net sets made by surface and mid- water (6 meter depth) method, respectively. According to the obtained data from surface One, 8 ½ mesh size constituted the highest proportion of total fish caught. A comparison of total weight caught by mesh size showed varying differences when tested with a one-way ANOVA.As well as, the results obtained by Duncan test indicated four distinct groups that the fish weight entangled from 8 ½ mesh size accounted for the major one. Analysis of data from 5 ¾ mesh size indicated that 30% of the catch fell out of the net during hauling. There was no significant difference between mean fork length among mesh size when tested with a one- way ANOVA. The results obtained from fish caught in three parts of net (top, middle, down) indicated that fish caught from the middle part were the highest proportion of total fish entangled. Similar to the surface catch method, 8 ½ mesh size caught highest proportion and weight to the total fish entangled in mid-water one. It needs to do further study to obtain the best mesh size for catching yellowfin tuna in surface catch method and depth of water for netting in mid-water catch method as well as to compare both methods.