Distinguishing between spring and autumn spawned herring from daily increments, a preliminary report

Abstract

Otoliths from Norwegian Spring Spawning herring larvae, collected on a cruise in May 1985 and North Sea Autumn Spawned herring larvae, collected on a cruise in Desember 1987, were examined for daily increments. A greater distance from the otolith nucleus to the first observed increment was seen in Norwegian Spring Spawning herring larvae (14.0 ± 3.4 µm) than in North Sea Autumn Spawned herring larvae (5.0 ± 1.6 µm). In addition the results indicate that species from autumn and spring spawning stocks can be separated by a comparition of the increment widths in the otoliths. In a distance between 40 and 60 µm from the nucleus, the increments in the North Sea Autumn Spawned herring larvae had a width less than 1.5 µm, while the corresponding widths in spring spawners were greater than 2.0 µm.