Cluster Analysis for Defining the Resource Distributed Area of North Atlantic Albacore Stock

Abstract

Albacore is the traditional target species for Taiwanese longline fleet in Atlantic Ocean. Three main geographical sub-areas in North Atlantic Ocean where Taiwanese longline fleet operated frequently were produced from three distinguished clusters, which were grouped from a total of 79 and 5×5 degree statistical blocks using cluster analysis. The overall mean CPUE (no. of fish per thousand hooks) from 4 main catch species, i.e., albacore (Thunnus alalunga), bigeye tuna (Thunnus obesus), yellowfin tuna (Thunnus albacares) and swordfish (Xiphias gladius) in the 5×5 degree statistical blocks during 1968-2002 were used in the cluster analysis. The changes of temporal nominal CPUE series from 4 dominant catch species in three sub-areas were examined. Sub-areas 2 and 3, located in subtropical and temperate waters respectively, were closely related for the higher albacore CPUE. Sub-area 1, in tropical waters, had the higher CPUEs of bigeye tuna and yellowfin tuna but the lower and fluctuated albacore's CPUE. The delineation of the sub-area in this study could be used in constructing the General Linear Models for standardizing the catch rate of this stock.