Seasonal bottlenecks in diet shifts and growth of smelt in a large eutrophic lake

Abstract

Seasonal growth of smelt Osmerus eperlanus was studied in the Kiihkelyksenselkä basin in the eutrophic Lake Hiidenvesi, southern Finland. The growth of age 1+ and 2+ year smelts was very low probably due to the discontinuous supply of large invertebrates Chaoborus flavicans and Mysis relicta. Diet shift back to zooplankton in autumn, suggested the existence of a bottleneck in the growth of these age groups. Slow growth rate was further intensified by the onset of maturity at age 2 years, combined with the high diet and habitat overlaps between similar-sized 1+ and 2+ year smelts. Older 3+ and 4+ year smelts shifted to piscivory, i.e. cannibalism, during the growing season, which was seen as rapid increases in their growth rates. © 2004 The Fisheries Society of the British Isles.