Does space matter? Optimizing stocking density of Holothuria arguinensis and Holothuria mammata

Stocking density is an important factor affecting growth in aquaculture. The main objectives of this study are to evaluate the effects of different stocking densities on Holothuria arguinensis and Holothuria mammata's growth and determine the optimal density. Four different stocking densities were selected for H.arguinensis (1, 3, 5 and 7 ind/0.2m(2)) and three for H.mammata (6, 10 and 12 ind/0.5m(2)). Growth (specific growth rate (SGR) and growth rate (GR)), weight change, coefficient of variation and productivity were estimated, additionally the feeding rate on H.mammata. Growth on H.arguinensis decreased as the stocking density increased, showing the higher growth at the stocking density of 1 ind/0.2m(2) (SGR: 1.24%/day +/- 0.16 and GR: 0.94g/day +/- 0.05), with a 104.65% (+/- 9.98) of weight change. The best H.mammata growth was registered at 10ind/m(2) (SGR: 0.56%+/- 0.04%/day and GR: 0.48 +/- 0.04g/day) and 25.48% (+/- 1.52) of weight change. H.mammata feeding rate decreased as stocking density increased. Crowding stress could be considered the main factor affecting the sea cucumbers growth and performance on our study. The optimal stocking density for H.arguinensis and H.mammata under tank-based conditions were established as 1 ind/0.2m(2) and 5 ind/0.5m(2) respectively. The critic biomass for H.arguinensis (471.65g/m(2)) and for H.mammata (988.11g/m(2)) were reached during the experiment at the fourth and fifth weeks respectively. Therefore, to ensure and increase growth of these species under tank, their biomass should be maintained under those thresholds.