Effects of juvenile nursery on geographic spawning distribution in Norwegian spring-spawning herring (Clupea harengus L.)

The Norwegian spring-spawning herring is characterized by a heterogeneous g rowth pattern originating from nurseries situated along the Norwegian coast and in the Barents Sea. Using a classification algorithm based on measurem ents of the three first scale annuli, the geographic, temporal, and age dep endent recruitment patterns of the coastal and Barents Sea components of mo st year classes from 1930 to 1989 were studied. The relative importance of each component in the year classes varied with the fluctuating stock size o bserved during the period studied. In periods with a low spawning stock alm ost no recruitment appeared from the Barents Sea juvenile areas, while at h igh stock levels the Barents Sea component totally dominated the spawning s tock. The asynchronous maturation of the two components caused a recruitmen t pattern characterized by a high proportion of the coastal component at yo unger ages and an increasing proportion of the Barents Sea component at old er ages. Both components recruited along the entire spawning range studied, and once fully recruited, no latitudinal gradient in the spawning stock co mponent composition was observed. (C) 1998 International Council for the Ex ploration of the Sea.