مقايسه كارآيي تله هاي تاشو با تله هاي قيفي در صيد شاه ميگوي درياچه مخزني سدارس

Comparative study of Opera House traps with Funnel traps for catching Astacus leptodactylus in the Arass water reservoir

Presently the crayfish fishermen in Arass water reservoir use only Funnel traps. This study was conducted in 2002, to aimed for evaluating the ability of catch, sex ratio and the size frequency of crayfish with the Opera House traps and Funnel traps. Forty Funnel traps including and forty Opera House traps have been set in 7.5 and 10m depth from May to July (in each depth combination of 20 number of the two type traps). The linking rope also the stone being used to stream line traps in the bottom of lake. The results revealed no significant differences (P>_0.01) between the average length and weight of the crayfish caught with the two types of trap in different months of the year. The CPUE with Opera House traps was greater than with Funnel traps and the number caught in 24 h in one trap of the former type was 2.26 number higher, which was significantly higher than Funnel traps . A greater quantity of male crayfish was caught with Opera House traps, but compared with Funnel traps in respect of male crayfish catch, the difference was not significant (P>0.05). Crayfish more than 120mm length (minimum standard size for commercial Arass crayfish) in Opera House traps comprised 87.56% of the catch, while by Funnel traps, the figure was 69.90 %. Considering these finding, it is proposed that the crayfish fisherman in Arass be allowed to use Opera House traps, because they are more likely to improve crayfish population sustainability.