The nucleus of the herring otolith as a racial character

Abstract

Significant differences between the size of the nucleus in the sagittal otolith of herring spawning at different seasons in the North Sea and the English Channel were demonstrated on material collected during the years 1964-1965 and 1968-1969. These dataconfirmed the results of Postuma and Zijlstra which showed that herring spawning early in the year have on average larger nuclei than herring spawning later. It appeared that the percentage of opaque nuclei in the different populations was inversely related to the mean nucleus size of these populations. Late autumn - winter spawning herring have on average higher percentages of opaque nuclei than herring spawning in early autumn. Within spawning populations nucleus size showed no relationship with length suggesting that differences in nucleus size distributions can only exist when the majority of herring spawns in the season in which they hatched.