Effect of Rearing Tank Background Color on Early Survival of Dolphin Larvae

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Abstract
The effect of experimental tank background color on early survival rates of dolphin larvae (Coryphaena hippurus) was examined to determine the survival rates of 7-d-old fish fed varying rotifer concentrations in different experimental systems. Fish were stocked into unpainted (tan) or painted (glossy black) fiberglass tanks and fed rotifers at densities of either 5, 10, 15, 20, or 50 animals/mL of water. Overall survival of larvae averaged 50% in black tanks and 25% in uncolored tanks. When directly compared, black tanks improved survival rates 130% over tan tanks. Survival was affected by rotifer stocking density in experiments with tan tanks and was maximum when larvae were fed 20 rotifers/mL. Survival was not affected by densities between 5 and 20 rotifers!mL in black tanks. It is concluded that the use of black tanks greatly enhances early survival rates of dolphin larvae fed rotifers. The effect is likely related in part to the contrast between feed items and the background tank color. This ...