ESTIMATION OF FISHING MORTALITY AND ABUNDANCE OF PACIFIC HERRING IN THE HUANGHAI SEA BY COHORT ANALYSIS (VPA)

In this paper Cohort Analysis (VPA) with the data on catch in number by age and year is used to estimate independently fishing mortality, abundance and actual number of spawning stock of the Pacific herring in the Huanghai Sea.The results show that catch rate of the fishery is very high, and that the fishing mortality of the dominant age group aged 2-4 was 0.87-2.97 during the years 1971-1984.The size of year class has been decreased since 1982 although the variability for this species in the Huanghai Sea is frequent.This results in reducing the recruitment of the fishery, the abundance and the actual number of spawning stock.Therefore, an urgent management measure should be considered.
The magnitude of several sources of errors in Cohort Analysis (VPA) are examined, and the precision of the estimates is mainly dependent on an accurate natural mortality.