The definition of point of no return of larvae and feeding characteristics of Alosa sapidissima larvae and juveniles

In order to better understand the feeding characteristics of Alosa sapidissima at the early development stage, the effects of starvation on growth and morphology, the point of no return(PNR)of A.sapidissima larvae, and the feeding rhythm of A.sapidissima larvae and juveniles were researched by experimental ecology approach at the water temperature of (20.5±1.0)℃.It has been clearly described that newly-hatched larvae were(7.45±0.15)mm in total length(TL), (2.01±0.06)mg in body weight(BW)and the yolk sac was(5.99±0.13)mm³ in volume.5 days after hatch(DAH), the yolk sac of A.sapidissima larvae was absorbed completely.Both TL and BW of control group increased gradually with the consumption of yolk sac and the establishment of exogenous nutrient.In contrast, the TL and BW of the starved larvae started to decrease from 6 DAH, and all the starved larvae died at 10 DAH;The first feeding time of A.sapidissima larvae was 3 DAH, the feeding rate reached 46.67%, the higtest feeding rate was 89.29% in 5 DAH, and the PNR was 7-8 DAH.According to the yolk sac absorption and PNR, the the optimal time of initial feeding should be 2-3 DAH.The feeding rhythm of A.sapidissima larvae and juveniles exhibited that the feeding peak of early stage larvae(4 DAH)appeared at 14:00, and the feeding amount reached 0.14 mg;the feeding peak of late stage larvae(17 DAH)was at 10:00 and 14:00, and the feeding amount was 0.92 mg and 1.36 mg, respectively;the juvenile at 28 DAH reached three feeding peaks at 10:00, 14:00 and 18:00, and the feeding amount was 1.77, 2.45 and 1.55 mg, respectively.Therefore, A.sapidissima was typically feeding only in daytime, and the feeing peak period was gradually prolonged with fish growth.The result of daily feeding situation of A.sapidissima showed the feeding rate in daytime was 20.08%(4 DAH), 29.48%(17 DAH)and 12.41%(28 DAH), which could be a reference for A.sapidissima daily feeding.