Abstract

Little to no information is published on the nutritional needs of fish outside of traditional aquaculture species. Such species are cultivated for rapid tissue growth and therefore have very different feeding requirements than many marine aquaria species. A nutrition study was initiated at Disney's The Seas with Nemo and Friends to determine plasma nutrient levels of marine teleosts housed in the Main Tank exhibit. Initial findings showed that, compared to broadcast feeding alone, the addition of aquatic gel to fish diets improved several plasma nutrient parameters. Blue striped grunts (Haemulon sciurus) were found to have decreases in plasma iron, zinc, magnesium, and phosphorus and increases in vitamins A and E when supplemented with aquatic gel. The aim of this study is to better understand the normal plasma trace mineral and vitamin levels of wild blue striped grunts so that captive diets can be adapted to best meet the nutritional needs of this fish species.

Sixty-three wild-caught blue striped grunts of similar size (mean 19.3 cm, range 16.5-25.6 cm fork length) were blood sampled during initial capture from the Florida Keys, at the completion of a 2 month quarantine period at The Seas, and after a month-long acclimation period in the Main Tank exhibit. During this period, fish transitioned from an unknown natural diet to a captive diet of krill and aquatic gel (Mazuri Reef Gel 57W9, Land-O-Lakes Purina Feeds LLC, Arden Hills, MN); food offered was recorded daily. Fish were housed in artificial saltwater upon arrival to quarantine and were exposed to a 21-day 0.2 ppm copper immersion and two 3-day courses of oral fenbendazole treatment (170 g per 100g of gel food) 7 days apart during quarantine. Water quality was closely monitored throughout the study and water samples were collected at the time of blood collection to perform water chemistry and trace mineral analysis.

For venipuncture, fish were anesthetized in a 70 ppm buffered tricaine methanosulfonate (Tricaine-S, MS-222, Western Chemical, Ferndale, WA 982248) aerated bath. On initial sampling, all fish were intramuscularly injected with an AVID transponder chip for future identification. Fish were weighed, body condition scored, and measured at each sampling. One percent of a fish's body weight of blood was collected from the caudal tail vein and placed in lithium heparinized tubes. Blood was centrifuged within 10 min of venipuncture, and plasma supernatant decanted and frozen at -80°C for later mineral (iron, zinc, copper, selenium, molybdenum, cobalt, manganese, sodium, potassium, chloride, calcium, phosphorus and magnesium) and vitamin (A and E) analysis at Michigan State University diagnostic laboratory.

Differences in plasma mineral and vitamin levels across the three sampling time points were analyzed by analysis of variance (ANOVA) using a repeated measures design. Post-hoc tests (Bonferroni method) were used to make pairwise comparisons and results were considered significant when P < 0.05. Preliminary results showed significant increases in plasma cobalt, copper, manganese, molybdenum, zinc, vitamin A, and calcium levels over the duration of the study. Plasma iron, selenium, vitamin E, potassium, and magnesium levels significantly decreased as fish transitioned from their wild diet to the captive diet. Plasma sodium and chloride levels remained unchanged. Water chemistry results are pending.

Determining the proper nutrient requirements for fish is complicated by the fact that fish can accumulate trace minerals both directly from their aqueous environment and from the diet they ingest. Data analysis of the study will help identify what adjustments to captive diets need to be made in order to better simulate natural diets for blue striped grunts.

Acknowledgements

The authors wish to thank Dr. M. Andrew Stamper, Jane Davis, Conrad Litz, Scott Martin, Todd Harmon, Jennifer Abderrazak, Megan Ratte, Allison Corwin, John Dickson, and others in the Seas Aquarium Department, as well as Dr. Debra Myers, Dr. Greg Fleming, Charlene Burns, Jane Capobianco, Andrea Varesco, Nikki Demoro, Amanda Romig, Karen Lopez, and Tanya Giannantonio for their assistance with this project.