Spawning and trends in spawning stock size of the North Sea mackerel during the period 1973-1980

Abstract

A declinining trend in the size of the spawning stock of North Sea mackerel is described by data obtained from egg surveys. During the period 1973-1980 the spawning stock size was reduced by 60-70%. A similar stock development has been demonstrated by VPA of catch data and on tagging results. An egg production curve for 1980 based on three egg surveys in the North Sea combined with daily sampling from a fixed position within the spawning area is given. Attempts are made to estimate the size of the spawning stock from the egg production curve and data published on fecundity.