Larval development and occurrence of morphological abnormalities in hatchery-reared Japanese flounder Paralichthys olivaceus larvae fed marine rotifer Brachionus plicatilis at different population growth stages

Abstract

We assessed the dietary value of rotifers at different population growth stages for hatchery-reared Japanese flounder, Paralichthys olivaceus, in terms of larval development and the occurrence of morphological abnormalities. Rotifer cultures were prepared daily and continued for up to eight days. Rotifers were harvested on day 2 from the start of batch culture (early-exponential growth phase), as well as on day 4 (late-exponential phase) and day 8 (stationary phase), and equally enriched with freshwater Chlorella containing n-3 HUFA. The flounder larvae were supplied until 24 days after hatching (DAH) with rotifers at each of these growth phases. During 18-30 DAH, larvae fed rotifers at the late-exponential growth phase showed higher performance in growth and morphological development than those fed stationary-phase rotifers. All groups of larvae were raised until approximately 40 mm total length (55 DAH), at which time the juveniles that had been fed late-exponential-phase rotifers had the lowest incidence of malpigmentation and/or skeletal malformation (p < 0.0001). The population growth stage of the rotifers used for enrichment had a large influence on the occurrence of morphological abnormalities in larviculture of Japanese flounder.