TROPICAL REEF-FISH DISEASE OUTBREAKS AND MASS MORTALITIES IN FLORIDA, USA - WHAT IS THE ROLE OF DIETARY BIOLOGICAL TOXINS

From November 1993 to February 1994, heavy mortalities of tropical reef fish were reported in the Palm Beach area on Florida's southeast coast and the Islamorada area in the upper Florida Keys. Severely affected fish were typically adult herbivores or omnivores such as the angelfishes Pomacanthus paru and P. arcuatus, the rock beauty Holacanthus tricolor, the cherubfish Centropyge argi, the princess parrotfish Scarus taeniopterus, the blue chromis Chromis cyaneus, the balloonfish Diodon holocanthus, the whitespotted filefish Cantherhines macroceros, the doctorfish Acanthurus chirurgus, and less severely affected, the reef butterflyfish Chaetodon sedentarius and the foureye butterflyfish C. capistratus. Diseased fish typically had lesions on the anterior part of the head, ulcerated body sores, fin and tail rot, and a heavy mucus coating on the body surface. Protistan parasites such as Brooklynella hostilis, Uronema marinum, and amoebae were common. Turbellarians and bacterial infestations were also detected. There is, however, no evidence that these potential pathogens are the principal cause of the disease syndrome and resultant fish mortality they may be secondary invaders of fish whose health has already been compromised. The possibility is considered that biological toxins from macroalgae such as Caulerpa spp., or from benthic dinoflagellates such as Gambierdiscus toxicus may act as principal stressors that influence reef-fish health. A possible link between some of the mass mortalities in Florida and those in the Caribbean in the past 15 yr is postulated. The causative chain of events leading to these mortalities should be studied in a larger ecosystem framework, but the immediate need for a program monitoring reeffish diseases is also discussed.