Abstract

In 2001 a pilot study was run in which juvenile Atlantic surgeon fish, blue tangs (Acanthurus coeruleus) and ocean surgeonfish (A. bahianus), were fed a washed green algae (Ulva sp) or one of two commercially available foods marketed for marine reef fish. Of the two commercial feeds tested, 27% of fish fed the premium flake developed lesions consistent with Head and Lateral Line Erosion (HLLE) syndrome compared to no lesion development in fish fed the premium pellet diet. One of the most obvious differences between the two feeds was the concentration of vitamin A, 35,433 IU/kg was measured in the flake diet compared to 287,210 IU/kg in the pellet diet.

In the current study, the effect of varying levels of vitamin A on growth and HLLE lesion development on these species was evaluated. Fish were divided into four treatment groups, one group was fed the premium pellet diet used in the previous study. The other three groups were fed a commercial finfish formula in which the concentration of vitamin A only was modified. The final concentration of vitamin A (as fed) in these three diets was 1907.2 IU/kg, 50,231.1 IU/kg, and 133,404 IU/kg, respectively. Fish were individually marked and housed in 76 L glass aquaria set up on a re-circulating system with artificial sea salt. There were five replicate tanks assigned to each treatment group and 2-4 fish of each species stocked into each aquarium.

Following an extensive quarantine and acclimation period, the introduction of experimental feeds began in April 2003 and the study ran for 14 weeks. During the study mortality was minimal in all groups, however there was a severe outbreak of lymphocystis affected blue tangs only in all 4 treatment groups. Obvious HLLE-like lesions were not observed in any fish fed the diet containing 133,404 IU/kg vitamin A. In the other groups, one ocean surgeonfish fed the premium pellet used in the pilot study developed HLLE following 8 weeks on the diet and the lesions persisted for the duration of the study. One blue tang fed the finfish starter diet (50,231 IU/kg) developed HLLE lesions following 12 weeks on the diet and lesions persisted for the duration of the study. Two ocean surgeonfish fed the low vitamin A diet (1907.2 IU/kg) developed HLLE lesions following 14 weeks on the diet.

Following 14 weeks of observation, activated carbon was added to the system to clarify the water. Within two weeks HLLE lesions became apparent in all treatment groups. With one exception, lesions were observed in ocean surgeonfish only. The development of lesions, and the number of fish affected, was greatest in ocean surgeonfish fed the low level of vitamin A. Though not conclusive, observations do support the hypothesis that low levels of dietary vitamin A may predispose captive Atlantic surgeonfish, particularly A. bahianus, to development of HLLE lesions.

Acknowledgements

The authors thank Florida Sea Grant and Disney's Animal Programs, The Living seas, Epcot, Walt Disney World Resort, for financial support of this research. We also thank RuthEllen Klinger-Bowen, Allen Riggs, Emily Marecaux, Theresa Floyd and Scott Terrell for technical assistance.