European smelt (Osmerus eperlanus) eats all; eaten by all: Is it a key species in lakes?

摘要

The concept of keystone species is controversial and often confused with dominant species. A modern definition is a species whose impact on the ecosystem is far greater than expected from its biomass (Power & Mills 1995, Power et al. 1996). European smelt {Osmerus eperlanus) is mainly considered a pelagic zooplanktivore species, but investigations have shown that it eats larger pelagic animals as well as small fish, and that it is phytoplanktivorous in its larval stages (Svaerdson 1976, Nilsson 1979, Naesje et al. 1987). Moreover, it utilizes the epibenthic habitat to prey on epibenthic invertebrates (Sandlund et al. 1980,1985a). European smelt is also an important prey species, eaten by a number of sympatric fish species (Nilsson 1979). It has been dubbed a "buffer species" by Svardson (1976). Thus, European smelt is an important component in a large number of trophic interactions in the pelagic ecosystem. In many Scandinavian cases, the presence of smelt is also considered a prerequisite for the occurrence of the desired large-bodied predatory brown trout (Salmo trutta) (Sandlund & Naesje 2000). In this paper we review data on trophic position of European smelt in the pelagic zone of Norwegian Lake Mjesa and discuss its role in the pelagic ecosystem.