Theses and Dissertations

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Defense Date

10-2008

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Jennifer S. Rehage

Second Advisor

Richard Spieler

Third Advisor

Shawn Liston

Abstract

Ecological communities consist of multiple predators and prey, in which predators have varied hunting strategies and foraging preferences and the prey have varied antipredator responses. Multiple predators can combine to have linear or non-linear effects that can either enhance or reduce the risk of predation experienced by prey. How this occurs in novel systems where predators and prey lack a coevolutionary history, and thus prey may be naïve to predation threats posed by non-indigenous predators, is not well understood. This study examined the predatory effect of two non-native fishes, the African jewelfish (Hemichromis letourneuxi) and the Mayan cichlid (Cichlasoma urophthalmus) and the behavioral responses of a native Everglades prey assemblage. We used an in situ enclosure experiment to compare predation rates and prey selectivity, followed by behavioral trials in the laboratory to examine predator foraging tactics and prey responses to predation (microhabitat use and activity levels). When both predator species were present, we found no evidence that native prey experience a release from predation resulting from interference competition. C. urophthalmus exhibited a higher predation rate and different foraging preferences than H. letourneuxi. Overlap in habitat domain of predators and prey was important in predicting prey consumption, as prey were most often consumed when they occupied the same space in the water column as predators. The predators were found to be functionally different and the behavioral responses of prey varied among species in response to the non-native predators. It is important to examine the behavior of predators and the responses of prey to determine the nature of these multiple predator interactions and the resulting impacts of non-native predators, especially as these predators continue to spread in the Everglades ecosystem.

Comments

Project funded by the Park Oriented Biological Support Initiative of the U.S. Geological Survey (POBS 06-086).

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