Changes in Growth and Feeding Characteristics during Early Ontogenesis in Threadsail Filefish, Stephanolepis cirrhifer

SIMPLE SUMMARY: Stephanolepis cirrhifer, a commercially important marine fish, has been listed on the IUCN Red List of Threatened Species owing to a sharp decline in its wild-caught numbers. To increase the survival rate of juveniles after hatching, the changes in growth and feeding characteristics during early ontogenesis in this species must be understood. In this study, the growth indices at 24, 28, 30, 40, 45, and 50 days post hatching (dph) were significantly higher than those at earlier time points, suggesting that the juveniles possessed well-developed digestive organs and that a compound feed is suitable for rapid growth at these stages. The obligatory mixed-nutrition period was brief, at only 3–4 dph, and the larvae reached the point-of-no-return (PNR) at 1.5–2 dph. Furthermore, the growth indices of juveniles fed only under light conditions showed clear peaks and troughs. This is indicative of daytime feeding behaviour. These results serve as a reference to guide larval rearing and feeding programs that can improve the survival rates of S. cirrhifer. ABSTRACT: Background: We investigated the growth and feeding characteristics of threadsail filefish, Stephanolepis cirrhifer, during early ontogenesis. Methods: The growth indices of hatchlings fed compound feed were measured from 0 to 50 days post hatching (dph). The absorption time of the yolk sac and oil globule, as well as the rate of first feeding were measured to characterise the early growth stage and determine the point-of-no-return (PNR). Feeding characteristics and rhythms were investigated under a light/dark cycle and under continuous light. Results: Growth indices increased significantly at 24, 28, 30, 40, 45, and 50 dph. The yolk sac and oil globules were completely absorbed before 4 dph, indicative of a short mixed-nutrition period at 3–4 dph. Under starvation conditions, the first feeding rate was highest (86%) at 0.5 dph and then decreased to 53.3% at 1.5 dph and 26.2% at 2 dph, suggesting that the PNR occurs at 1.5–2 dph. The feeding peak appeared at 15:00–18:00 and under light conditions, while the feeding trough appeared at 0:00–3:00. Conclusions: Compound feed supplied adequate nutrition for early growth and development. The peaks and troughs of feeding times were indicative of daytime feeding behaviour. These results provide guidance for successful rearing of filefish seedlings and juveniles.