Spatial variation of growth and gonadal developments of Maurolicus muelleri in the Norwegian sea and in a Norwegian fjord

This study uses samples of the mesopelagic fish Maurolicus muelleri (Gmelin) collected in spring 1995 as part of the Norwegian interdisciplinary Mare Cognitum research program. Spatial patterns in life-history parameters such as gonadal developments, fecundity and growth between the Norwegian Sea, coastal areas and Herdlefjorden were studied. Differences and similarities could be distinguished. More cohorts seemed to be present in the Norwegian Sea than at the coast or in the fjord. The fjord and coastal fish showed a higher proportion of gonad mass and higher fecundity relative to their body mass than those from the Norwegian Sea, The gonadosomatic index of fjord and coastal fish was over three times that of the Norwegian Sea fish; mean oocyte size for all fish was also larger. Among the ten largest oocytes, mean diameters of 347 and 497 mu m at the coast and in Herdlefjorden, respectively, indicate that these were hydrated oocytes and that spawning had begun there. Spawning had not, however, commenced among fish from the Norwegian Sea. The overall results indicate an increasing trend in maturation stage, gonadal investment, relative fecundity and growth rate in the samples studied from the Norwegian Sea to the coast and towards the fjord.