Individual growth and variance of Japanese sea cucumber (Apostichopus japonicus) reared in closed cages

The cause of variance in the individual growth of Japanese sea cucumber (Apostichopus japonicus) was investigated by rearing individuals in closed cages. Two groups of sea cucumbers were used: a group of small individuals each weighing approximately 30 g, and a groups of large individuals each weighing approximately 160 g. Each individual was kept in a separate rearing cage. The rearing cages were submerged along the breakwater in Esandomari fishing port. The mass of the sea cucumbers was recorded every month, and ambient water temperature was also recorded. Overall, the specific growth rate (SGR) of the sea cucumbers was found to be negatively correlated with ambient temperature. The mass variance of the small group was significant, which may be attributed to the fluctuation of threshold temperature for aestivation. In the small group, seasonal SGR patterns of low-growth individuals were different from the patterns of high-growth individuals. This difference was another cause of variance. The mass variance of the large group, however, was not significant, as the threshold temperature for aestivation was not fluctuated in the test period. Diet was also considered one of the important factors leading to growth variance.