Long-term trends in ten non-target North Sea fish species

Catch data on 10 non-target fish species from the International Bottom Trawl Survey during the years 1970–1993 are analysed for changes in distribution and abundance by size class. Trends in catch rates of spurdog, starry ray, bib, poor cod, four-bearded rockling, grey gurnard, bullrout, long rough dab, dab, and lemon sole have been compared using correlation and cluster analysis with indices describing different aspects of the North Sea ecosystem, including biomass of pelagic, demersal and industrial species, temperature, eutrophication, and beam trawl effort. Most species appear to have increased over the period. However, the statistical analysis does not provide a plausible explanation of the factors responsible for the observed changes.