Abstract

Coral reefs worldwide are stressed and degrading from climate change, overfishing and pollution. Fishing pressure has re-duced the numbers of top predators in reef ecosystems and nutrient pollution has led to increased macroalgae, both of which may be influencing fish health. In the Caribbean, important fish herbivores, particularly in the genus Acanthurus, are exhibiting black spots, a sign of ectoparasite presence. Marine Protected Areas (MPAs) have been established to help pre-serve coral reefs and their inhabitants primarily by restricting fishing and other destructive activities, however these measures may not be protecting top predators and fish health. We hypothesized that if top predators exist they should feed on heavily infested Acanthurids and thus reduce ectoparasite infestation. We used timed underwater surveys at 11 sites around Tobago, Grenada, Carriacou and the Tobago Cays; 6 sites inside MPAs and 5 sites outside to test this hypothesis. Photographs were taken of all piscivores and Acanthurids encountered. Numbers/hour of each were derived from the pho-tos as well as the percentage of Acanthurids with black spots. Predator and Acanthurid abundances were higher inside MPAs than outside but they were not significantly different. Percentages of Acanthurids with ectoparasites were similar inside and outside MPAs. No significant correlations were found between black spot occurrence and predator abundances. However, the number of predators capable of consuming adult Acanthurids was close to zero with no large groupers, snap-pers or sharks encountered. Our results show MPAs do not appear to protect top predators or improve fish health with re-gard to ectoparasite infestation. A gill net and illegal spearfishing were witnessed within 2 of the MPAs indicating poor enforcement may be largely to blame.

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