Publication Abstract

Linking spatial pattern of bottom fish assemblages with water masses in the North Sea

Siegfried Ehrich, Vanessa Stelzenmüller* and Sara Adlerstein

Understanding the links between large scale spatial structuring of fish assemblages and shaping factors is essential to develop ecosystem-based fisheries management and to assess the impacts of climate change. In this study, we investigated spatial patterns of bottom fish assemblages in the North Sea in relation to prevailing water masses in the region. We based our analysis on catch data from the German Small-scale Bottom Trawl Survey (GSBTS) conducted between 1987 and 2005 and used multivariate statistical techniques. Spatial variation in species composition of bottom fish assemblages among areas covered by the survey was larger than annual variation. Five significantly different and persistent bottom fish assemblage clusters were distinguished associated with the following prevailing hydrographical regimes: i) the English channel, ii) continental coastal, iii) central North Sea, iv) northern North Sea, and v) northern Atlantic water masses. Associations were generated by gradients in relative proportions of abundant species such as grey gurnard (Eutrigla gurnardus), dab (Limanda limanda), whiting (Merlangius merlangus), haddock (Melanogrammus aeglefinus) and Norway pout (Trisopterus esmarki). Our results strongly support the hypotheses that hydrographical features such as water masses, fronts, and residual currents are the mayor forces shaping bottom fish associations in the North Sea. Spatial demarcations of bottom fish assemblages indicated by this study can be used to develop ecosystem-based fisheries management strategies.

Reference

Siegfried Ehrich, Vanessa Stelzenmüller* and Sara Adlerstein (2009) Linking spatial pattern of bottom fish assemblages with water masses in the North Sea. Fisheries Oceanography 18, 1 : 36-50