The accumulation of nutrient-rich waste in aquaculture systems poses environmental challenges, particularly in monoculture setups. The warty sea cucumber (Apostichopus parvimensis, WSC) has shown potential for managing solid waste through integrated recycling. This study aimed to evaluate the growth, performance, and waste removal capabilities of WSCs when fed waste from white seabass (Atractoscion nobilis, WSB). The objectives were to determine the optimal feeding ration of WSB waste for WSCs and assess how WSC size influences growth, performance, and waste removal.
Three trials were conducted to address our objectives. In Trial 1, WSB waste nutritional quality was measured for changes over five days in seawater without WSCs. In Trial 2, 45 WSCs (100-150 g) were fed 1%, 2%, 3%, 4%, or 5% of body weight to determine the effects of daily ration on growth and waste removal capacities. In Trial 3, 45 WSCs were divided into three size classes (<100, 100-150, >150 g) and fed 4% of body weight to assess the impact of size on performance. Environmental parameters were monitored throughout the trials, with temperature ranging from 14.8°C to 23.4°C, pH from 7.82 to 8.30, dissolved oxygen from 7.76 to 11.16 mg/L, salinity from 30 to 35, and total ammonia nitrogen from 0.013 to 0.06 mg/L. All trials were conducted in 175 L tanks, run in triplicate, with regular measurements of waste, feces, and growth.
In Trial 1, the nutritional quality of WSB waste remained stable, with nitrogen content ranging from 2.96% to 3.5% and carbon content from 33.27% to 40.88%. In Trial 2, WSCs fed at 4% of body weight had a significantly higher specific growth rate (SGR) of 1.06% per day compared to other rations. Ingestion rate (IR) increased with higher feeding rations, ranging from 0.11 g DW/ind/day at 1% body weight to 0.58 g DW/ind/day at 5%. Fecal rate (FR) followed a similar trend, peaking at 0.30 g DW/ind/day in the 5% group. Apparent digestibility ratio (ADR) varied between 44.78% and 77.84%, with no significant differences between treatments. Waste removal efficiency (WRE) was highest at 4%, ranging from 28.75% to 44.05%. Standard length and width (SLW) measurements showed that WSCs fed at 4% had the highest SLW increase rate of 2.31% per day. In Trial 3, small WSCs demonstrated significantly higher nitrogen removal efficiencies, ranging from 42.67% to 48.71%, and carbon removal efficiencies from 34.95% to 48.16%, compared to large WSCs. The IR for large WSCs was 0.70 g DW/ind/day, significantly higher than the 0.30 g DW/ind/day for small WSCs. FR ranged from 0.12 g DW/ind/day for small WSCs to 0.29 g DW/ind/day for large WSCs, with ADR ranging from 57.10% to 59.84% across size classes. This study confirms WSCs as efficient waste removers, particularly when fed at 4% body weight. Smaller WSCs showed superior waste removal and growth, highlighting their role in optimizing bioremediation. Future research should explore long-term trials and scalability in larger commercial aquaculture systems.