CPUE standardization for Pacific saury fishery in North Pacific using GLM and spatial-GLM model

Fishery-dependent catch per unit effort (CPUE) is often used as an index of abundance in stock assessment models. However, nominal CPUE could be affected by many variables including spatial-temporal factors or environmental factors in addition to stock size. The assumed proportionality between observed CPUE and stock abundance could be shifted by these factors. CPUE standardization, which involves statistical analyses to remove the effects of variables on CPUE other than abundance, has become a routine when fishery-dependent data are used in the fishery stock assessment. In the present study, we used conventional generalized linear model (GLM) and spatial-GLM model to standardize the Pacific Saury fishery in North Pacific. Environmental factors including sea surface height (SSH), sea surface temperature (SST), and sea surface temperature gradient (SSTG) were incorporated as covariates in the full models. AIC was used as a criterion to select the best model for both GLM and spatial-GLM, respectively. The selected best GLM and spatial-GLM consisted of SST and SSTG. The results of the standardized CPUE derived from the best GLM and best spatial-GLM were compared.