Abstract

One of the challenges of managing marine reef fish populations and their associated ecosystems is identifying how components of habitat affect the growth, reproductive success, morbidity/mortality, and distribution of managed species. Compounding this is the impact of human activity on habitat. The most common measures of fish habitat quality include food availability, shelter, predation risk, and access to mates and resources for reproduction. One aspect of habitat quality that has been largely ignored is risk of disease and parasitism. This study focuses on a particularly detrimental external fish parasite, monogenean trematodes (Neobenedenia). Monogeneans were quantified from the skin of two species of surgeonfishes collected at four sites in the U.S. and British Virgin Islands. Habitat locations were chosen because they vary in proximity to human activity and thus may differ in water quality and biodiversity. Parasite loads among Acanthurus coeruleus varied significantly among sites. The highest loads occurred on fish collected from three shallow bay sites, while virtually none of the fish collected from an offshore cay (Flat Cay, St. Thomas USVI) were infected. Of the 90 ocean surgeonfish (A. bahianus) collected only 3% were infected with monogeneans compared with nearly 55% of the similar-sized blue tang (A. coeruleus) from the same sites. To determine if ocean surgeon are less susceptible to infection by trematodes, both species were translocated from Flat Cay to an aquarium where they were exposed to high densities of trematodes, but not permitted the opportunity to visit cleaning stations. When transferred into captivity blue tang from Flat Cay acquired a substantial number of monogeneans over a 3-week period while ocean surgeon from the same site were relatively unaffected. Species differences in habitat use within sites are also examined for their role in explaining the observed differences in monogenean loads between species

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