SS1.09 Fisheries Population Linkage Spatial and Temporal Variation in Zooplankton
Date: Wednesday, June 12, 2002
Time: 2:15:00 PM
Location: Carson C
 
RickelS, H. Steinitz Marine Biol. Lab., Hebrew Univ., Eilat, Israel, atos@vms.huji.ac.il
Genin, A, , H. Steinitz Marine Biol. Lab., Hebrew Univ., Eilat, Israel, amatzia@vms.huji.ac.il
 
FISH FEEDING ON DRIFTING PREY: SELECTIVE PREDATION ON ZOOPLANKTON PATCHES
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Site-attached planktivorous fish have no control on the time they spend foraging within a patch of prey. Mechanisms determining the efficient use of zooplankton patches by coral-reef dwelling fish were experimentally studied in a flume, controlling current velocity, density and distribution (homogeneous Vs patchy) of prey. Predation on patches roughly 1000 times the mean density of the homogeneously distributed prey, exhibited enhancement of feeding rates unexplainable solely by increases in prey density. Empirically estimated predator’s handling time and search efficiency along with prey densities of the patchy prey were incorporated into the Holling’s disk equation. The predicted functional response was shown to reproduce much of the observed trends in the attack, but not in the feeding rates. Disparities between the observed and predicted functional responses suggest that fish selectively orient their attacks on micro-aggregations of prey (mm scale), rather than on isolated individuals. This allows the fish to capture several prey per strike. As a result, the fish predation rate, as a function of prey density, did not level off, not even in exceedingly high prey density.