Fish in the Structure and Function of Freshwater Ecosystems: A "Top-down" View

The role of fish in regulation of the structure and function of freshwater ecosystems (lakes and streams) is examined with respect to effects resulting directly from their feeding activity, indirectly from size or other forms of prey selectivity, and from influences on nutrient cycling and transport. That fish have long had a legitimate place in limnological research is documented by a review of limnological books, texts, and journals. Recognition of their "top-down" effects, started largely from Czechoslovakian research (Hrbáček and others) in the mid-1950's, was popularized by American and German research (Brooks, Jacobs, and others) in the mid-1960's and has enjoyed a remarkable upsurge in the 1970's, continuing into the 1980's. Although size-selective predation has been an important phenomenon in stimulating widespread research on effects of fish on freshwater communities and their function, the importance of other mechanisms in such regulation is considered.