Optimal stocking densities were investigated for the sea cucumber Apostichopus japonicus Selenka under feed-supplement and non-feed-supplement regimes in net enclosures for 333 d. Substantial weight loss occurred during the aestivation phase (AE). Decreased growth rates were also observed during the winter phase (WT). In contrast, sea cucumbers showed rapid growth during the spring (SP) and autumn (AU) phases. Feeding regimes considerably influenced the growth performance, i.e., sea cucumbers grew faster under feed-supplement regime than under non-feed-supplement regime (P < 0.05). The average survival rates of sea cucumbers under feed-supplement regime were higher than those under non-feed-supplement regime for both the autumn phase and spring phase, but the differences were only significant for the latter phase (P < 0.05). The fitted B-N curves showed that the optimal stocking densities, in terms of net production, were 22.3 ind. m -2 for feed-supplement regime and 14.1 ind. m -2 for non-feed-supplement regime.

The goal of this study was to determine the point of no return (PNR) for Acipenser sinensis larvae and their growth in relation to delayed initial feeding. During the experiment at 23.2 AE 0.8°C, the initial feeding rates increased from 7.7 to 73.7% in larvae at age 7-12 dph (days post-hatch). When delayed initial feeding was conducted at 14 dph, the initial feeding rate was as low as 37.3%. The rate declined even further thereafter, thus the PNR was assumed to have been reached by 14 dph. The survival rates were more than 80% at 7-2 dph, thereafter falling dramatically. Total lengths of larvae and body weights increased gradually and reached the maximum at 12 dph, then decreased and were even less than those at 7 dph. It was concluded that the optimal time for exogenous feeding was at 9-10 dph.