The influence of flood cycle and fish predation on invertebrate production on a restored California floodplain |
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Authors: | Edwin Grosholz Erika Gallo |
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Institution: | (1) Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA |
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Abstract: | Although floodplains are known to be tightly controlled by the flood cycle, we know comparatively little about how flooding
influences predators and their consumption of secondary production, particularly in highly seasonal floodplains typical of
Mediterranean climates. In this study, we investigate how the seasonal dynamics of a central California floodplain influence
the timing and magnitude of fish predation and the abundance and composition of invertebrates. For 3 years (2000–2002), we
compared changes in abundances and size distributions of invertebrates through the flood season (January–June) with seasonal
changes in the abundance of larval and juvenile fishes. Using diet analysis of fishes and manipulative feeding experiments
with fishes in field enclosures, we link specific changes in invertebrate populations directly to feeding preferences of seasonally
abundant fish. Early in the flood season prior to March, we found little influence of fish predation, consistent with the
near absence of larval and juvenile fishes during this period. Coinciding with the midseason increase in the abundance of
larval and juvenile fishes in April, we found significant declines in zooplankton abundance as well as declines in the size
of zooplankton consistent with fish feeding preferences. Our results were consistent with results from feeding enclosure experiments
that showed that fish rapidly depressed populations of larger cladocerans with much less effect on smaller cladocerans and
calanoid copepods. At the end of the flood season, zooplankton abundances rapidly increased, consistent with a switch in the
feeding of juvenile fish to aquatic insects and subsequent fish mortality. We also found that zooplankton biomass on the floodplain
reached a maximum 2–3 weeks after disconnection with the river. We suggest that floodplain restoration in this region should
consider management strategies that would ensure repeated flooding every 2–3 weeks during periods that would best match the
peaks in abundance of native fishes.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. |
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Keywords: | floodplain predation zooplankton benthic invertebrates fishes top– down |
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