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Notes
- Abstract:
- Successful settlement of larval reef fish from the pelagic to benthic environments has implications for population dynamics and recruitment rates for most reef- associated fishes. While this event has been studied extensively in terms of macropredation and resource availability, little has been done to examine the impact that reef-associated micropredators may have on Caribbean reef fishes. On St. Thomas, U.S. Virgin Islands, I investigated this relationship using a local and abundant parasitic isopod, Gnathia marleyi, and four species of territorial damselfishes. Susceptibility to gnathiid isopod infestation was tested in laboratory conditions using adult Stegastes diencaeus, S. adustus, S, variabilis and S. leucostictus. Susceptibilities were found to vary between species forming two groups: S. variabilis and S. leucostictus were similarly susceptible while S. diencaeus and S. adustus were similarly susceptible to each other but more susceptible than the other two species. Rates of parasite infestation on juveniles were explored in situ using caged fish set on the reef at dusk or dawn. Rates of parasitism occurrence ranged from 14% in new recruits less than 20mm fork length to 33% in fish with a fork length greater than 40mm. The effects of gnathiid isopod abundance on the behavior of new recruits was further investigated with a pairwise choice experiment. Here, I found that new recruits would choose areas of plankton addition over food barren areas, regardless of whether the plankton included parasitic gnathiids. However, when faced with a choice of gnathiid enriched plankton or non-gnathiid plankton, fish were found to prefer non-gnathiid plankton.
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