|Abstract: ||abstract:We compared geographical distributions of Pacific saury, Cololabis saira (Brevoort) (Scomberesocidae), fishing stocks in the Northwest Pacific (NWP) for 3 yearly groups of high, average, and low abundances, using the Taiwanese fishery catch per unit effort (CPUE) data from 1994 to 2002. Two migratory groups, inshore and offshore, were found in averageand low-abundance years, while an additional oceanic migratory group, which spread eastward to around 178°E in Oct., was found in the year of high abundance. Most of the saury groups were distributed in areas
where the sea surface temperature (SST) ranged between 10 and 20°C with a high aggregation around 15°C, implying that 15°C is the preferred temperature for saury to aggregate intensively for the commencement of the spawning migration, and to move southward to spawning grounds where SSTs of around 20°C are favorable to their offspring. The timing, abundance, and geographical distributions of fish aggregations of migratory saury were associated with SSTs. In the early stages of the fishing season, apparent warming caused by the intrusion of Kuroshio Current waters in the southern NWP was closely related to delayed aggregation and low abundances of the saury stock; in contrast, cooling of the waters affected by Oyashio waters was related to eastward aggregation and high abundances of saury. High saury abundances occurred in low-temperature areas.
Specifically, in years of low CPUE values, sea water temperatures (SWTs) of the fishing grounds were higher than 15°C, while in years of average and high CPUE values, the SWTs of the fishing grounds were < 15°C. Therefore, fishing ground SWTs higher than 15°C (around 16°C SST) is an indicator of low stock abundances of saury in the NWP.