SPATIAL PATTERNS OF THE TEMPORAL DYNAMICS OF 3 GADOID SPECIES ALONG THE NORWEGIAN SKAGERRAK COAST

Time series from an extensive research survey of juveniles of cod Gadu s morhua, pollack Pollachius pollachius and whiting Merlangius merlang us sampled from 1919 to 1994 at 38 stations along the Norwegian Skager rak coast were investigated. Spatial and temporal analyses were perfor med to study the spatial pattern of the temporal dynamics of the 3 fis h species. Spatially consistent variations were detected in abundance, year-to-year fluctuation as well as in periodicity. The spatial heter ogeneity occurred at a mesoscale (differences between fjords) and at a local scale (differences between stations within a fjord) for the 3 g adoids. However, the magnitude of the spatial heterogeneity differed b etween species. Cod and whiting, which were more abundant in sheltered areas, showed higher spatial variability than pollack, which was more abundant in exposed locations. In this way, the spatial pattern of ab undance appeared to be linked to the scale of variability of the speci es. All 3 species exhibit periodic fluctuations of 2 to 2.5 yr in thei r optimal habitats, which probably resulted from intrinsic interaction s in age-structured populations, such as density-dependent competition and cannibalism. In addition, all the species exhibited long-term tre nds possibly due to extrinsic forces, such as environmental changes or anthropogenic influences.