Variations in abundance and distribution of demersal fish species in the coastal zone of the southeastern North Sea between 1980 and 1993
van Leeuwen, P.I.; Rijnsdorp, A.D.; Vingerhoed, B. (1994). Variations in abundance and distribution of demersal fish species in the coastal zone of the southeastern North Sea between 1980 and 1993. CM Documents - ICES, C.M. 1994(G:10). International Council for the Exploration of the Sea: Copenhagen. 12 + tables + figures pp.
Deel van: ICES CM Documents - ICES. ICES: Copenhagen. ISSN 1015-4744, meer
This paper presents a first comprehensive analysis of the fish catches of the beam trawl surveys carried out in the Scheldt estuary, the Dutch part of the Wadden Sea, the shallow zone of the continental coast between Belgium and the Horns Reef and offshore areas in the southern and southeastern North Sea. The species composition is analysed and compared among areas. Species richness varies between 32-49 species, and is highest in the coastal waters compared to the estuaries or offshore waters. Species richness further increased from the inner German Bight towards the southern North Sea and towards the central North Sea. The Shannon-Weaver index of diversity is generally low due to the dominance of flatfish species in both inshore and offshore areas (e.g. dab, plaice) and shows a similar geographical pattern as species richness. Indices of diversity and evenness appeared to be rather stable over the years, except for a low in 1988 and 1991. These lows could be related to the exceptional high catch of dab and gobies, respectively. The annual variation and trends in species abundance is analysed for a selection of species. The species selected comprised of the resident estuarine and coastal species, dominant flatfish species which enter the coastal waters. Out of nine resident estuarine species studied, 4 species tend to decrease in recent years (eelpout, sea nail, flounder and eel) and 5 show a variable pattern. The trends in abundance are not always consistent among areas. The three flatfish species dab, plaice and sole that use the coastal waters as nursery ground show a decrease in catch rates since the late 1980s in all areas. Out of 8 open sea species, the solenette, scaldfish, lesser weever, grey gurnard show a substantial increase in abundance since the late 1980s.
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