Transition from endogenous to exogenous feeding in longfin yellowtail Seriola rivoliana larvae under simultaneous effects of daily temperature fluctuation and enrichment of the rotifer Brachionus rotundiformis

The most sensitive period in fish larva culture occurs when larvae must make the transition from endogenous to exogenous feeding, where temperature and nutrition are suggested as the primary factors affecting development and survival. However, little is known about its simultaneous impact during this period. This study aimed to determine the effect of two temperature regimes and rotifer enrichment at the first feeding of longfin yellowtail Seriola rivoliana . Eggs were subjected to a constant 24°C (CTE) and a daily temperature fluctuation (DTF) between 22.8–25.2°C until oil droplet exhaustion, 5.5 days after hatching. Inside the temperature treatments, the impact of three rotifer enrichment products (Ori-green, S.presso, and a Domestic emulsion) for the euryhaline Brachionus rotundiformis was evaluated. Results showed that larval survival was higher and larvae were bigger at DTF compared to CTE at oil droplet exhaustion. At the same stage, larval size from rotifer enrichments resulted bigger at Domestic emulsion compared to Ori-green. The relative expression of trypsin gen in larvae aged 3.7 DAH was higher at Domestic emulsion compared to S.presso emulsion and Ori-green. This study indicates that daily temperature fluctuation and Domestic emulsion can improve larval performance at first feeding. Domestic emulsion is probably a potential rotifer-enricher for longfin yellowtail larvae.