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In order to know about the dynamics of the saury population in the Pacific Ocean off northern Japan, the catch and effort statistics of the saury lift net fishery were analysed. The abundance index and the effective over-all fishing intensity for every 10-day period was calculated, and the yearly and seasonal variations of the available population were examined in relation to the fishing intensity. Although the catch showed a clear trend of decline after 1962, the abundance of the saury population appeared to be maintained until 1967. The fishing intensity was considered to be reduced since the latter half of the 1950's. The seasonal change of the abundance had a general trend, but it varied from year to year. The role of fish-ing intensity in seasonal variation was not clear because the total coefficient of decrease during the season showed apparently negative correlation with the fishing intensity of the season. Certainly immigration and emigration of fish from the fishing ground played an important role in the seasonal variation. Some discussions on the effect of oceanographic conditions, such as the distribution of water masses on the migration of saury, have been given.

Abundance Index and Dynamics of the Saury Population in the Pacific Ocean off Northern Japan