Yolk-sac absorption and point of no return in Chinese sturgeon Acipenser sinensis larvae

This study aimed at determining the point of no return (PNR) for Chinese sturgeon when in transferring fromyolk absorption to first external feeding of Chinese sturgeon larvae, and their growth in relation to the PNR. During the experimental period temperature range from 22 to 24°C, the yolk-sac volume of the newly hatched larvae was 52.3 mm3 becoming distinctly reduced during the period from 4 dph (days post hatching) to 7 dph and most critically until 10 dph. Mixed feeding of larvae was initiated 24 h before the yolk-sac was fully exhausted. The initial feeding rate was reached with a maximum of 73.7% of the larvae at 13 dph with a range of 9 to 17 dph. When start-feeding was conducted at 15 dph, the initial feeding rate was as low as 37.2% of the test larvae. Thereafter the rate declined further and the point of no return (PNR) was assumed to have been reached on the 14th day after hatching.