Evaluation of seaweed, Ulva lactuca as a fresh diet for nursery stage of golden rabbitfish, Siganus guttatus

Ulva lactuca is a green seaweed with a high potency to be used as fish diet. The feeding trial aimed to evaluate the use of U.lactuca as fresh diet for the nursery of golden rabbitfish Siganus guttatus. Five treatments were evaluated, namely 100% fresh Ulva (FU), the combination of fresh Ulva and dry pellet with the ratio of 75:25% (UP1), 50:50% (UP2), 25:75% (UP3), and 100% dry pellet (DP) with three replicates. Golden rabbitfish with a mean initial weight of 6.2 g were stocked into fifteen rearing tanks at a density of 20 fish tank−1. After 90 days, growth responses differed significantly amongst dietary groups. Fish fed DP had similar weight gain (219.86%) to UP3 (232.21%), and its specific growth rate (1.29%/day) was similar to UP2 (1.11%/day) and UP3 (1.33%/day), but significantly different (p<0.05) from FU (SGR -0.25%/day; WG -19.97%). The survival rate of fish fed UP2 (98.33%) was significantly different (p<0.05) from FU (80.00%). The fish body color fed FU had bright yellowish color and high carotenoids (14.69 µg g−1) compared to DP. The combination of fresh Ulva with pellet at the same ratio of 50% and 25:75% similar to the 100% pellet diet can support the fish growth.