Ardea
Official journal of the Netherlands Ornithologists' Union

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De Nie H. (1995) Changes in the inland fish populations in Europe in relation to the increase of the Cormorant Phalacrocorax carbo sinensis. ARDEA 83 (1): 115-122
Fish populations in Europe react on increasing eutrophication in a general pattern. However this pattern is locally different and strongly depends on the 'natural', pre-eutrophicated situation. The general trend is toward unstable fish populations with dominance of small, short living, early maturing fish like Perch Perca fluviatilis, Ruffe Gymnocephalus cernuus, Smelt Osmerus eperlanus and/or carp-like fish (cyprinids) mainly Roach Rutilus rutilus and Bream Abramis brama. The high-bodied Bream is negatively selected for by Cormorants in favour of Roach, Perch, Ruffe or Smelt. Social fishing on shoaling young fish of species like Perch, Ruffe, Smelt and Roach in relatively turbid, eutrophic lakes with few submerged water vegetation can be considered as an adaptation of the inland breeding population of Cormorants to eutrophication caused by human activity. Where lakes and rivers are still clear and relatively unpolluted, the Cormorant returns to its habit as solitary hunter, predating on Eel Anguilla anguilla, Trout Salmo trutta or cyprinid species of running waters like Chub Leuciscus cephalus.


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