Inter-annual variability in distribution and spatial abundance of sprat, Norway pout and small herring in the North Sea

Spatial explicit ecology and new regulations call for continuous spatiotemporal data. For marine species, such data hardly can be obtained from observation but need to be modelled from point data. A promising approach is regression kriging that addresses biological response to environmental conditions and spatial autocorrelation in data. Here it was applied to abundance data of North Sea prey fish sprat, Norway pout and herring. Results show seasonal and inter-annual variability of distribution limits, core areas and high abundance areas of all three species. Core areas of sprat and Norway pout are complementary bordering roughly along the 50 m isobaths. Small overlap of the two core areas were found only off the northern English coast. The comparison of North Sea-wide sums with assessment estimates show that the regression kriging approach can reproduce inter-annual dynamics. The outcomes allow assessing the magnitude of the catchability of the employed fishing gear and give evidence of seasonal variation of catchability. Capabilities and restrictions of the applied model and data are discussed in the light of niche theory. Results are of potential use in the assessment of the effects of changed utilization of marine areas in the marine spatial planning framework.