SS1.09 Fisheries Population Linkage Spatial and Temporal Variation in Zooplankton
Date: Wednesday, June 12, 2002
Time: 11:45:00 AM
Location: Carson C
 
HolzmanR, Hebrew University of Jerusalem and the InterUniversity Institute for Marine Sciences, Eilat, Israel, roi@pob.huji.ac.il
Genin, A, , Hebrew University of Jerusalem and the InterUniversity Institute for Marine Sciences, Eilat, Israel, amatzia@vms.huji.ac.il
 
PREDATION ON ZOOPLANKTON BY NOCTURNAL FISH: EFFECTS OF LIGHT, FLOW, AND PREY DENSITY
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Zooplankton predation by the nocturnal fish Apogon annularis was quantified over a coral reef in Eilat, Red Sea. Feeding rates were estimated based on the depletion of prey downstream of caged fish. Measurements were made under a wide range of natural light intensity, flow speed and zooplankton density. Fish fed selectively on large-bodied zooplankton (> 1mm) at a mean rate of 0.14 prey/min. Feeding rates increased linearly with prey density, while changes in light intensity and flow speed had a negligible effect. Flume experiments indicated a small effect of light on the fish's strike distance and reactive volume. A simple model using these parameterized effects explained most of the trends observed in situ. The feeding rates of these nocturnal fish were considerably lower than those of diurnal zooplanktivorous fish. However, in terms of carbon gained, the larger body size of the nocturnal prey may compensate for lower feeding rates during the night.