Feeding indicators and bioremediation ability of warty sea cucumber Neostichopus grammatus fed potential wastes from abalone Haliotis midae farming

The reuse of aquaculture waste to produce valuable sea cucumber biomass promises to reduce environmental impacts of aquaculture and increase incomes. This study aimed to assess the suitability of potential waste from abalone farming as feed for the warty sea cucumber Neostichopus grammatus and infer bioremediation effects from sea cucumber feeding. Four diets: abalone waste, fermented algae (sea lettuce Ulva lacinulata) mixed with sand (U+S), abalone pelleted feed, and sand, were fed to N. grammatus under controlled conditions for 6 wk. Sea cucumbers fed sand exhibited a significantly higher (p < 0.001) ingestion rate (1.35 +/- 0.04 g ind..-1 d-1) than other diets. Those fed U+S (1.03 +/- 0.02 g ind..-1 d-1) had a significantly higher ingestion rate (p < 0.001) than those fed abalone waste and pellet. However, the ingestion rate was similar for pellets (0.67 +/- 0.07 g ind..-1 d-1) and abalone waste (0.54 +/- 0.02 g ind..-1 d-1) (p = 0.138). Ingestion and faecal production rates were inversely influenced by the diet's total organic matter content (TOM). The faecal TOM of sea cucumber fed abalone waste, pellet, and U+S decreased from the TOM of the diet by 37.53 +/- 1.63% (p < 0.001), 31.39 +/- 0.53% (p < 0.001), and 48.83 +/- 9.81% (p = 0.03), respectively. There was a decrease (37.74 +/- 0.12%, p < 0.001) in the carbon content of sea cucumber faeces fed pellet compared to the feed, while there was no difference in nitrogen (p = 0.08) content. The carbon content of sea cucumber faeces fed U+S was not significantly different (p = 0.11) from that of the feed. However, the nitrogen content decreased by 63.00 +/- 8.27% (p = 0.03). This study shows that wastes from abalone farming are acceptable food for N. grammatus, affirms the bioremediation potential of N. grammatus through integrated multitrophic aquaculture, and recommends its coculture trial with abalone.