TRIAL ESTIMATION OF STANDARDIZED CATCH PER UNIT EFFORT OF YELLOWFIN TUNA BY THE TAIWANESE LONGLINE FISHERY IN THE TROPICAL WATERS OF THE ATLANTIC OCEAN

SUMMARY The trial standardized catch per unit effort (CPUE) of Atlantic yellowfin tuna caught by Taiwanese longline fishery was estimated by general linear models (GLM). For the manipulation, several factors were used including year, quarter, subarea, vessel category and the two-way interactions. Before estimating CPUE, historical catch and effort data were selected and re-examined by spatial and temporal distribution in the tropical core fishing area; then the 1990-2011 catch and effort data within the tropical core area (15 o N- 20 o S) were selected and stratified into five subareas to make the nominal CPUE as homogeneous as possible among subareas by cluster analysis. The GLM and Delta-GLM were used to standardize yellowfin tuna CPUE for the Taiwanese longline fishery in the Atlantic tropical waters. The results obtained show a very similar trend except for the displacement of peaks in the series. Discrepancies occurred between the Japanese longline CPUE series and any one of the three Taiwanese series. Logically, the comparison suggests that the applicability of Standardized CPUE for yellowfin tuna by the Taiwanese longline fishery in the Atlantic Ocean warrants verification and refining before the stock assessment session.