SS3.18 Habitat Coupling in Lakes
Date: Thursday, June 13, 2002
Time: 11:15:00 AM
Location: Esquimalt
 
HoelkerF, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, hoelker@igb-berlin.de
Mehner, T, , Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, mehner@igb-berlin.de
 
FORCED HABITAT COUPLING BY PISCIVORE-MEDIATED SPATIAL BEHAVIOUR - AN INDIVIDUAL-BASED APPROACH
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A spatial explicit individual based model including bioenergetic principles was used to simulate observed diel habitat shifts of roach (Rutilus rutilus L.) between littoral and pelagic areas of the mesotrophic Lake Großer Vätersee. By this it was possible to study the relevance of habitat coupling for diet, zooplankton consumption, activity costs and mortality. The movement of a simulated fish follows a 'correlated random walk'. Swimming direction and moving angle are calculated stepwise with a certain random deviation. The habitat selection rules of roach allow a fish to select a habitat that maximizes its expected probability of survival, considering both nutritional status of an individual and mortality risk. Roach with low energy reserves were more willing to accept mortality risks in exchange of higher food intake. The simulation results provide evidence for the interpretation of diel migrations as a trade-off defined by food availability and predation risk in different habitats. It can be speculated that the plasticity in the type of littoral-pelagic linkages can be understand as a evolutionary response of roach to the wide range of different predator combinations.