Standardizing CPUE of Longtail Tuna (Thunnus tonggol) caught by Gillnet Fisheries fleet of Iranian waters of the Oman Sea using General Linear Model (GLM)

Longtail Tuna (Thunnus tonggol) is one of the most important Commercial and Neritic fish species which are widely distributed throughout neritic tropical and temperate waters of Indo-Pacific. The aim of this study was to determine relative index of abundance of Longtail Tuna from 2007 to 2016, also we evaluated effect of some explanatory variables (Year, Month, Vessel tonnage and net height) of catch per unit effort data in traditional gillnet fishery standardized by general linear model (GLM) in the Oman Sea. Standardized catch per unit effort is an important entrance in stock assessment as an annual abundance index. The results of this study have shown that year and month as explanatory variables influence CPUE significantly in GLM model with lognormal error distribution, but the increasingly effect of vessel tonnage and net height were not significant. Relative index of abundance of Longtail Tuna has shown increasing trend from 2007 to 2016 with the highest pick in 2013, that is shown catch rate can increase by raising catch effort. There is a seasonal trend in standard CPUE of Longtail Tuna with the highest catch rate in warm season. Monthly relative index of abundance has shown highest catch rate occurred in May and June.