Abstract
In Lake Ringsjon, southern Sweden, we estimated yearly variations in both 0+ and older fish abundances, following the fish reductions in 1988–1992. Between 1987 and 1994, the total planktivore biomass decreased fourfold whereas the abundance of 0+ fish increased twenty times. The resulting change in predation pressure from planktivorous fish on zooplankton increased up to 2–3 times, after the fish reduction. We conclude that after an initial decrease, the predation pressure on zooplankton increased considerably due to the increase in 0+ fish abundance. The expansion in juvenile fish abundance may therefore have been an important factor behind the apparent lack of top-down effect on the zooplankton community following biomanipulation of Lake Ringsjon. The horizontal distribution of 0+ fish in Lake Ringsjon is also discussed.
Published Version
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