Egg Weight in Atlantic Herring (Clupea harengus L.)

Abstract

The dry weight of mature herring eggs, measured from samples taken from about 25 spawning grounds, is very variable from ground to ground, while there may also be age and year-to-year differences. The mean weight varies by at least a factor of three, from 1·2 mg per egg in Baltic spawners of the late spring, to 3·7 mg per egg for early winter spawners of the southern North Sea. In general egg weight is high for fish spawning in winter and early spring, and low in late spring, summer and autumn. As a characteristic it can be useful for defining “races” as well as having wide ecological implications. Usually fecundity and egg weight are inversely related. Thus spawners with fewer, heavier eggs will produce few, but large larvae with considerable yolk reserves at a time of poor food supply and a low predator population. Under warmer conditions a larger number of small eggs are produced which can be seen as an adaptation to adequate larval food, but high predation.

Author notes

^*Present address: Institut für Meereskunde der Universität Kiel, Hohenbergstrasse 2, Germany.

^**Natural History Department, Marischal College, Aberdeen, Scotland.