The objectives of the present study were to evaluate the yolk-sac and oil globule absorption and point of no return （PNR） ofpikeperch （Sander lucioperca L.） larvae. Artificial propagation ofpikeperch was performed...The objectives of the present study were to evaluate the yolk-sac and oil globule absorption and point of no return （PNR） ofpikeperch （Sander lucioperca L.） larvae. Artificial propagation ofpikeperch was performed at （15±2）℃. Yolk-sac absorption, oil globule absorption, larval growth and the first initial feeding rate were observed to analyze the early growth and to determine the PNR of pikeperch larvae. The total length of newly hatched （0 day after hatching, DAH） pikeperch larvae was （4.25±0.22） mm and the volume of the yolk-sac and the oil globule was （0.30±0.12）mm^3 and （5.14±2.28） 10-2 mm^3 respectively. The yolk-sac and the oil globule were exhausted at 11 DAH and 14 DAH, respectively. Pikeperch larvae began feeding at 8 DAH with an initial feeding rate about 10.0%. From 9 to 14 DAH, the initial feeding rate increased rapidly, and reached its highest （about 82.7%） at 14 DAH. It declined thereafter, 48.9% at 15 DAH and 35.6% at 16 DAH, thus the pikeperch larvae reached PNR by 15-16 DAH. The appropriate first feeding time for the pikeperch larvae is 11-12 DAH, when the initial feeding rate is higher than half of the maximum initial feeding rate.展开更多
At a temperature of 23.0 - 24.8℃, the mixed feeding of Japanese anchovy larvae was initiated 24 h before the yolk-sac was exhausted. The point of no return （PNR） was reached on the 6th day after hatching. On the 4t...At a temperature of 23.0 - 24.8℃, the mixed feeding of Japanese anchovy larvae was initiated 24 h before the yolk-sac was exhausted. The point of no return （PNR） was reached on the 6th day after hatching. On the 4th day after hatching, the pectoral angle appeared in both fed and unfed anchovy larvae although it was more evident and sharper in the starved and the PNR stage larvae than in the fed ones. According to observations of larvae collected in the sea, the pectoral angles were evident not only in the larvae of 3.62 - 7.44 mm in standard length, but also in the larvae of 2.70 mm in standard length with remnants of yolk. The pectoral angles became diffuse when the larvae reached 7.84 mm and vanished at 9.86 mm. The pectoral angle cannot be used as a criterion to distinguish healthy from starving larvae.展开更多
基金Supported by the Science Fund of Jiangsu Province(No.BY2015039-10)the Fund of Jiangsu Province Collaborative Center of Regional Modern Agriculture&Environmental Protection(No.HSXT219)the Science Fund of Changshu Science and Technology Bureau,China(No.CN201408)
文摘The objectives of the present study were to evaluate the yolk-sac and oil globule absorption and point of no return （PNR） ofpikeperch （Sander lucioperca L.） larvae. Artificial propagation ofpikeperch was performed at （15±2）℃. Yolk-sac absorption, oil globule absorption, larval growth and the first initial feeding rate were observed to analyze the early growth and to determine the PNR of pikeperch larvae. The total length of newly hatched （0 day after hatching, DAH） pikeperch larvae was （4.25±0.22） mm and the volume of the yolk-sac and the oil globule was （0.30±0.12）mm^3 and （5.14±2.28） 10-2 mm^3 respectively. The yolk-sac and the oil globule were exhausted at 11 DAH and 14 DAH, respectively. Pikeperch larvae began feeding at 8 DAH with an initial feeding rate about 10.0%. From 9 to 14 DAH, the initial feeding rate increased rapidly, and reached its highest （about 82.7%） at 14 DAH. It declined thereafter, 48.9% at 15 DAH and 35.6% at 16 DAH, thus the pikeperch larvae reached PNR by 15-16 DAH. The appropriate first feeding time for the pikeperch larvae is 11-12 DAH, when the initial feeding rate is higher than half of the maximum initial feeding rate.
文摘At a temperature of 23.0 - 24.8℃, the mixed feeding of Japanese anchovy larvae was initiated 24 h before the yolk-sac was exhausted. The point of no return （PNR） was reached on the 6th day after hatching. On the 4th day after hatching, the pectoral angle appeared in both fed and unfed anchovy larvae although it was more evident and sharper in the starved and the PNR stage larvae than in the fed ones. According to observations of larvae collected in the sea, the pectoral angles were evident not only in the larvae of 3.62 - 7.44 mm in standard length, but also in the larvae of 2.70 mm in standard length with remnants of yolk. The pectoral angles became diffuse when the larvae reached 7.84 mm and vanished at 9.86 mm. The pectoral angle cannot be used as a criterion to distinguish healthy from starving larvae.
