Influence of spring warming on the predation rate of underyearling fish on Daphnia - a deterministic simulation approach

Authored by T Mehner

Date Published: 2000

DOI: 10.1046/j.1365-2427.2000.00551.x

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative Flow charts

Model Code URLs: Model code not found

Abstract

1. According to previous field studies in the biomanipulated Bautzen reservoir (Germany), a midsummer decline of the dominating zooplankter, Daphnia galeata, was suggested to be initiated by a simultaneous occurrence of low fecundity of the daphnids and a selective feeding of underyearling fish on mature daphnids. The timing of both processes was assumed to be triggered by spring water temperature. However, the field data were not appropriate for testing whether yearly differences in spring warming are strong enough to control the predation rate of underyearling fish on daphnids. 2. By combining field data on fish growth, feeding and population mortality, the daily uptake of Daphnia by a virtual population of underyearling perch (Perca fluviatilis) was simulated, in addition, the daily predatory mortality of mature daphnids was calculated independently. Scenarios with a warm and a cold spring were compared. Furthermore, the delayed warming of a pelagic zone of a lake versus a littoral one was simulated. Sensitivity of the simulation to changes in five parameters was tested. 3. In both the warm spring scenario and the littoral warming scenario, more daphnids in general and more mature daphnids in particular were eaten, compared with the cold spring and pelagic scenarios. The predatory mortality of mature daphnids was driven by the increasing gape size of growing fish such that in warmer years the fish reach earlier the size at which they can eat mature daphnids. 4. The simulation was most sensitive to changes in daily mortality rate of the fish and to the size at maturity of the daphnids. Since at least the fish mortality is also temperature-dependent via the growth rates of fish, the predation rate of perch on D. galeata in Bautzen reservoir is substantially increased during a warm spring. This underlines the assumption that even a slight global warming may have a decisive influence on food web processes due to the fine-scaled patterns of trophic interactions in lakes.

Tags

Individual-based model Population-dynamics Planktivorous fish Perch perca-flavescens Community structure Zander stizostedion-lucioperca Eutrophic lake-tjeukemeer First-year growth Yellow perch Biomanipulated reservoir