Role of fish parasites in freshwater ecosystems with an example of parasites of the European smelt (Osmerus eperlanus).
The european smelt Osmerus eperlanus was accidentally introduced (in or before 1968) into the ecosystem of the Syamozero lake in Karelia (north-western Russia). The population of this species has reached a high density and caused serious changes in the structure and trophic relationships of the fish community of the Syamozero ecosystem. The microsporidian Glugea hertwigi has become a new and superdominant parasite of the smelt in this ecosystem. The invasion of microsporidia caused a mass death of fish, leading to changes in the population structure of the smelt and lowered fish catches. This study, which included data collected in most years from 1973 to 1996, suggested that parasites have a role in the regulation of fish community structure in freshwater ecosystems.