Assessment of the effect of depth and soak time on the catch rate for trapped Pharaoh Cuttlefish in Gargoor using generalized linear model (Case Study: Bushehr Port)

The purpose of this study was to investigate the effects of depth and soak time of Gargoors on catch per unit of effort (CPUE) for Pharaoh Cuttlefish (Sepia pharaonis (Ehrenberg, 1831)). The sampling time was February-March 2017, which was coincided with the cuttlefish fishing season operated by the Gargoor fishing vessels of Bushehr port. Randomly a total of 20 Gargoor fishing vessels were sampled. The Jackknife resampling method was used to obtain more reliable estimates. Also, the Generalized Linear Model (GLM) was used to determine the relationship between depths and soak time (explanatory variable) with catch per unit of effort (response variable). According to Jackknife resampling (similar to the results of the field observation), for 2–8 days soak times than 8–14 days soak times (545.720> 509.759) and 25–40 m depths than 10–25 m depths (536.940> 516.494) the average catch per unit of effort for Pharaoh Cuttlefish was higher. Besides, based on the above resampling, the catch per unit of effort confidence intervals for soak times of 2–8 days and 8–14 days also the depths of 10–25 m and 25–40 m were 382.671-708.768, 386.225-633.293, 347.822-685.126, and 410.345-693.535, respectively. On the other hand, the results of the generalized linear model showed that both depth and soak time of Gargoors had a significant effect on the catch per unit of effort (p<0.1); such a way that, increasing the depth and decreasing the soak time increase catch per unit of effort. However, based on field data, it is expected that if Gargoor fishing vessels with operating at depths of 25-40 meters and submerging their Gargoors within 2–8 days, they could be able to perform better CPUE for Pharaoh Cuttlefish according to the fishing effort used.