Vitelline utilization under the joint influences of temperature and photoperiod in the Ussuri catfish (Pelteobagrus ussuriensis)

The joint effects of temperature (18-30 °C) and photoperiod (0-24 h) on yolk utilization in the yolk-sac larvae of Pelteobagrus ussuriensis were investigated under laboratory conditions using a central composite design (face-centered) and response surface methodology. The results indicated that a suitable environmental temperature and photoperiod significantly increased yolk utilization. In contrast, unsuitable environments (e.g., low temperatures and complete darkness; low temperatures and continuous lighting; high temperatures and complete darkness; and high temperatures and continuous lighting) significantly reduced yolk utilization, albeit to varying degrees. Temperature affected yolk utilization independently of photoperiod, and was more important than photoperiod. Yolk utilization was synchronous with larval growth, showing the conversion of vitelline nutrients into larval growth. Predicated upon the reliable second-order relationship of yolk utilization with temperature and photoperiod, the optimal temperature-photoperiod combination was derived via model optimization and verified. The application of our results may help to increase the efficiency of seed production in the larviculture of this species.