SS1.09 Fisheries Population Linkage Spatial and Temporal Variation in Zooplankton
Date: Wednesday, June 12, 2002
Time: 11:30:00 AM
Location: Carson C
 
TischlerG, Institute for Limnology, Austrian Academy of Sciences, Mondsee, Austria, Gerhard.Tischler@oeaw.ac.at
Krois, C, , Institute for Limnology, Austrian Academy of Sciences, Mondsee, Austria, 
Wanzenboeck, J, , Institute for Limnology, Austrian Academy of Sciences, Mondsee, Austria, Josef.Wanzenboeck@oeaw.ac.at
 
CONCURRENCY OF ZOOPLANKTON POPULATION DYNAMICS WITH 0+ PERCH (PERCA FLUVIATILIS) PREY SELECTIVITY IN A PELAGIC LAKE HABITAT
image
Field consumption estimates have generally failed to predict impacts of 0+ fish feeding on lower trophic levels due to inadequate sampling techniques and inaccurate calculations of feeding rates. We used a combination of different gear types (push-net system, purse seine) to obtain more precise abundance estimates of the pelagic 0+ perch population in a lake habitat. Further, daily food consumption estimates were calculated for pelagic 0+ perch during summer of 1999 using a gastric passage time (GPT) model instead of traditional evacuation models. Gut fullness data in two-hours intervals from four 24-h cycles were included. Perch feeding rates on the main prey organisms (Daphnia sp., Bosmina sp., copepods) were calculated and compared with prey productivity rates to assess predatory impact of fish. Perch prey selectivity shifted from copepods during their first three weeks of life to Bosmina sp. and finally to Daphnia sp. Shifts in prey selectivity of 0+ perch coincided partly with population breakdowns of the main prey groups.