Percid fishes are found in lakes that cover a wide range of trophic conditions. The responses of percids and their habitats to progressive cultural eutrophication are predictable. Alterations in physicochemical characteristics of habitats precipitate changes in phytoplankton, macrophytes, zooplankton, and benthos that are ultimately deleterious. Enrichment can lead to favorable responses in percids, but somewhere in the continuum of trophic conditions the responses become unfavorable. The relative level at which the response becomes negative varies with the species according to tolerances to altered environment, adaptabilities to new habitat and forage base, and reproductive behavior. Progressive eutrophication acts as a selective mechanism that leads to a predictable sequence of fish species. Other perturbations, such as exploitation and habitat modification, can act synergistically with cultural eutrophication in accelerating the sequence. As eutrophication proceeds, the succession of species may not lead to increased fish yield because part of the nutrient load may be channeled through unharvestable food chains. Key words: Percidae, habitat, eutrophication, species dominance, food habits, parasitism, disease

A review of literature suggested that yield of Eurasian perch, Perca fluviatilis, in Lake Constance was greatest with moderate eutrophication. During eutrophication (1950–76), changes also took place in food, growth, distribution, and diseases of perch. Differences in perch between Lake Constance and other German or Alpine lakes of various degrees of eutrophy were found with respect to growth, yield, the relation of growth to yield, food, and the relation of food to growth. Similarities were apparent for perch in these lakes in terms of their age composition, age at maturity, and mortality. Only limited data were available for pikeperch, Stizostedion lucioperca, mainly on stocking success, yield, and growth. The status of percids in Lake Constance indicates that eutrophication has led to conditions favoring percids. Key words: Percidae, Lake Constance limnology, eutrophication, yield, Perca fluviatilis, food, growth, distribution, disease, Stizostedion lucioperca

The upper basin or Obersee of the Bodensee still retains all the fish species described more than four centuries ago, though rapid changes have recently been noted in many aspects of the fish community and of the Bodensee ecosystem. Though a variety of non-native species have been introduced, including a number of European and North American salmonids, none has become a prominent part of the community. The famous Blaufelchen, a pelagic coregonine, has recently been threatened by a combination of increasingly intensive exploitation, beginning at a low minimum size, compounded by an increasing growth rate of the species due to low population density, and due to increased planktonic food as a result of eutrophication. Consequently, by the early 1960s, the fishery came to exploit large yearlings, and few Blaufelchen survived to spawn. Eutrophication has reached a stage that is marginal to a number of deeper, benthic coregonines and char. Cyprinids, usually inshore, have expanded greatly, have invaded the pelagic habitat, and are subject to periodic mass mortalities. Other of man's effects are identified as are management measures now in practice.

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