STANDARDIZATION ON NORTHERN ATLANTIC ALBACORE (THUNNUS ALALUNGA) CPUE, DATING FROM 1967 TO 2012, BASED ON TAIWANESE LONGLINE CATCH AND EFFORT STATISTICS

SUMMARY The Taiwanese longline fisheries have been one of the major fleets operating in the North Atlantic for albacore resource since the mid-1960s. Catch statistics of North Atlantic albacore (Thunnus alalunga) compiled from Taiwanese longline fisheries from 1967 to 2012 were thus investigated in an attempt to elucidate the abundance fluctuations of this resource. The Taiwanese longline CPUE was separately standardized into three periods (1967~1987, 1987~1999 and 1999~2012). The generalized linear model (GLM) with log-normal error distribution was adopted for the standardization of both yearly and quarterly catch-per-uniteffort (CPUE) trends. Factors of year, quarter, subarea and bycatch effects of bigeye tuna, yellowfin tuna and swordfish were constructed into the model to obtain the yearly standardized abundance trend. Factors of quarter-series, subarea, and bycatch effects of bigeye tuna, yellowfin tuna and swordfish were constructed into the model to obtain quarterly the standardized abundance trend. The results show that the yearly standardized CPUE highly fluctuated before the mid-1980s, and then continuously declined up to the mid-1990s. Thereafter, it remained relatively stable up to the present. Similar trends were also obtained for the quarterly standardized CPUE series. RESUME