Effects of an Inert, Palatable Resource Subsidy on Live Prey Selection by Juvenile Fish
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. School of Environment and Natural Resources Undergraduate Research Theses; 2012
Resource subsidies, defined as energy and nutrients that enter ecosystems from external sources, can have diverse and complex effects on consumer populations. For example, resource subsidies can increase consumer growth rates and survival by direct ingestion of the subsidy or by increasing populations of other natural prey. Excessive rates of resource subsidy addition, however, can reduce habitat quality through eutrophication. In this study, I tested the effects of three different rates of manufactured feed (i.e., a resource subsidy) provision (no feeding, 1%, or 3% body-weight/day; BW/d) on the foraging habits and growth rates of age-0 channel catfish (Ictalurus punctatus) in earthen ponds. I hypothesized that increased feeding rates would increase populations of zooplankton prey in ponds; alter the amount, composition, and preference of natural prey ingested by the fish; and reduce dissolved oxygen concentrations in ponds. I found that increasing the feeding rate did not increase the density or alter community composition of zooplankton in ponds. Although the feed was ingested by fish in the 1% and 3% BW/d ponds and increased fish growth, fish in all feeding treatments still ingested the same types and amounts of natural prey as they grew through time. Surprisingly, the fish ingested larger insects and chironomid larvae during early life and then switched to smaller zooplankton later, opposite of the pattern that has been observed for most other fishes. Finally, increasing the feeding rate decreased dissolved oxygen concentrations in ponds. From an applied aquaculture perspective, natural prey may have an important role in the growth of juvenile channel catfish. Future studies should further examine the interactive effects of resource subsidies, habitat quality, and consumer ontogeny on diet patterns in highly subsidized ecosystems.
Related Item:Academic Major: Environmental Science
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