Effects of different seaweed diets on growth, digestibility, and ammonia-nitrogen production of the sea cucumber Apostichopus japonicus (Selenka)

Powdered algae is an essential ingredient in the artificial diet of the sea cucumber Apostichopus japonicus (Selenka) in aquaculture systems. In this study, growth performance, apparent digestibility coefficients, and ammonia-nitrogen production of A. japonicus fed six different granulated macroalgae diets (Sargassum thunbergii, Sargassum polycystum, Zostera marina, Ulva lactuca, Laminaria japonica and boiled L. japonica) were quantified for 60d to identify the optimal diet for this species. The type of seaweed ingested greatly affected the growth, ingestion rate, digestibility, and ammonia-nitrogen production of A. japonicus. Sea cucumbers grew faster when fed the U. lactuca or L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The ingestion rate was much higher when fed the U. lactuca, L. japonica, Z. marina, or boiled L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The apparent digestibility coefficients of the test diets ranged from 9.63% to 15.84%. Ammonia-nitrogen production was much lower in A. japonicus fed the U. lactuca or L. japonica diet compared to the other seaweed diets. The results of this study indicate that U. lactuca and L. japonica are optimum seaweeds for use in the culture of the commercially valuable sea cucumber A. japonicus. ► The first study to use ammonia-nitrogen production as an indicator to evaluate feed quality. ► The results will give good suggestion for formulated feed of A. japonicas and for seaweed culture. ► The research showed that L. japonica and U. lactuca are the best choice in sea cucumber culture.