Nauplii of the Calanoid Copepod, Acartia sinjiensis as an Initial Food Organism for Larval Red Snapper, Lutjanus argentimaculatus

Abstract

Initial feeding traits of larval red snapper Lutjanus argentimaculatus were investigated by supplying nauplii of the calanoid copepod Acartia sinjiensis and rotifers. The gut content of larvae consisted solely of A. sinjiensis nauplii (mean 2.1-7.2 nauplii/larva) on 0-2 days after initial mouth opening (days 0-2) . The mean body width of the nauplii ingested was 0.058 mm on day 0, subsequently increasing with larval age. Feeding on rotifers (mean lorica width, 0.117 mm) was observed from day 3 (mean 0.92 rotifers/larva), with the number ingested increasing markedly on days 4 and 5. The mouth width of red snapper larvae on day 0 (0.166-0.188 mm) was larger than the body width of the nauplii and rotifers but smaller than those of other fish species conventionally reared using only rotifers. This small mouth size may have been initially restrictive, allowing only the seizure of early nauplii at the onset of feeding. The larvae grew well from 2.84 mm in mean total length (TL) on day 0 to 3.38 mm TL on day 5, without significant mortality. Nauplii of A. sinjiensis constitute a promising initial food for early red snapper larvae and very likely also for those of other marine fishes with a small mouth size.