Fishes of the North Sea include over 200 species exhibiting widely differing ecological characteristics. There is a wealth of literature and, in this paper, we have restricted ourselves to providing generalized data on the more abundant species, with a view of highlighting those aspects which link the total fish community to the biotic and abiotic environment. There is necessarily a bias towards commercial species, because most of the pertinent information is related specifically to fish which are heavily fished. However, since there are few abundant species which are not exploited, the ecological links of the total fish community to other components of the system are well represented by the selection. Moreover, exploitation of the fish community may have indirectly affected the ecological relationships in the entire system. It follows that an understanding of the impact of fisheries on the fish community is likely to play a key role in helping us to understand how the North Sea ecosystem functions. The paper highlights various ecological aspects of the fish fauna including population dynamics, spawning in time and space, distribution, variations in year class strength, feeding, density-dependent growth and changes in species composition. Despite long time series of quantitative biological information for individual species and the obvious impact of fisheries on longevity and productivity of the fish community, the general conclusion is that it remains very difficult to separate effects of fisheries and of the environment on reproductive success, in which the variation is the most important destabilizing factor in the regulation of exploited fish populations. Another conclusion is that the spatial heterogeneity of the fish community in the North Sea is a factor of considerable concern in trying to link fish production to other components. It would seem likely that, to improve our understanding of the ecological linkages in the entire system, the spatial differences must be taken into account and a split of the area into a small number of rather more homogeneous units for studying fish population dynamics might be necessary. This approach is hampered, however, by the fact that fisheries statistics are not routinely reported at such small scales. For these to be made available, a complete reorganisation of international fisheries statistics would be required.
