مرکز منطقه ای اطلاع رساني علوم و فناوري - تعيين چشمه استاندارد توركوشگير ماهي گيدر در درياي عمان (سواحل سيستان و بلوچستان )

چكيده لاتين :

This study was conducted for examining the yellowfin tuna catch from surface and mid-water gill nets set of five net stretched mesh sizes including 145 (Control, filament size of 36/210 D), 170,197,215 and 237 mm (filament size of 54/210 D) with a net height of 14 m, made of nylon twine (Polyamide) and a hanging ratio of 1:2 through Lange boat in Oman sea (Sistan and Baluchistan province). It should be mentioned that the 145 mm mesh size was not considered in the last one method because of some reasons. Of 22 nettingʹs made on March (8 times) and May (14 times) 2002, 19 and 3 nettingʹs were made by surface and mid-water (6 meter depth) ones, respectively. According to the data obtained from surface one, the 215 mm mesh size constituted the highest proportion of both total and gilled yellow fin caught. Acomparison 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 obtained from 215 mm mesh size accounted for the major one. Analysis of data from 145 mm mesh size indicated that 30% of the total catch fell out of the net during hauling and lifting on board. This is an indicative of being unsuitable of the mesh size for catching the species in the local water. 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 came from the middle part were the highest proportion of total fish captured. According to the results, the mesh size of 215 mm is the best mesh size for catching yellow fin tuna in the surface gill net and will be a suitable replacement for the 145 mm mesh size. Similar to the surface gill net, 215 mm mesh size caught the highest proportion and weight to the total fish captured in mid-water one. It needs to do further study to compare the two gill nets mentioned above through the same mesh sizes in the same situation (time and area) as well as obtaining the best depth for netting in mid-water gill net.