The Effect of Towing Duration on the Catch per Unit of Swept Area (CPUA) from the Bottom Trawl Surveys in the Persian Gulf

This study was conducted to record best towing duration for bottom trawl surveys to stock assessment in the Persian Gulf. Shannon-Wiener, Margalef and evennes index were calculated for four towing duration (60, 90, 120 and 150minutes) in fishing grounds of Persian Gulf. A stratified random procedure was used for the survey sampling. The mean CPUA differed significantly with towing duration (P < 0.05) for the T. lepturus. The mean Shannon-Weiner diversity index differed significantly between four towing duration with higher Shannon-Weiner diversity index for 120minutes (2.81±0.44) (F=5.38; P=0.03. The mean CPUA differed significantly between towing durations with lowest CPUA at 150 minutes (P < 0/05). Results showed that 120minutes towing duration was the best for scientific surveys. 150 minutes towing duration was not suitable for scientific surveys in the Persian Gulf. The present research provided the first comprehensive study on the effect of trawl duration on diversity index and CPUA in Persian Gulf.