Rearing techniques to enhance first-feeding performance in mottled spinefoot (Siganus fuscescens) larvae

Abstract The mottled spinefoot ( Siganus fuscescens ) is a herbivorous marine fish species, and its aquaculture offers the potential to reduce the dependence on fishmeal in aquafeeds. However, high mortality during the early larval stages limits stable fingerling production. The aim of this study was to improve larval survival by optimizing rearing light intensity and exploring potential causes of early feeding failure. Larvae were reared under six light intensities (125, 500, 2000, 8000, 16,000, and 24,000 lx) using size-sorted, miniaturized rotifers cultured at elevated temperatures. Rotifer size selectivity during early feeding was also examined. Survival rates significantly improved to 9% under high light intensities (16,000–24,000 lx), compared to < 0.1% at light levels of 8000 lx and lower. This increase in survival coincided with a reduction in rotifer size, with lorica lengths decreasing from 171.94 ± 16.86 µm to 152.91 ± 21.10 µm. Chesson’s selectivity index showed that larvae exhibited higher ingestion rates of rotifers < 90 µm in lorica length during the first 2 days, while from days 3 to 8 of feeding, they ingested higher quantities of rotifers < 110 µm in lorica length. These findings indicate that S. fuscescens larvae require higher light intensity and smaller-sized rotifers during their early larval stages to enhance their survival.