Induced spawning and larval rearing of captive yellowfin porgy, Acanthopagrus latus (Houttuyn)

Abstract

Females of yellowfin porgy ( Acanthopagrus latus) were induced to spawn by a single injection of 1000 IU kg −1 human chorionic gonadotropin (hCG), 0.5 ml kg −1 Ovaprim (sGnRH-A in combination with domperidone) or a combination of hCG (500 IU kg −1) with Ovaprim (0.25 ml kg −1). Ovaprim, at a dosage of 0.5 ml kg −1, was the most effective. Fish injected with propylene glycol or 500 IU kg −1 body weight of hCG did not spawn at all. Fertilization rates ranged from 72 to 84% and hatching rates were between 60 and 88%. The hatched larvae were reared in 30–45 t cement tanks and fed initially on trochophore oyster larvae ( Crassostrea gigas), followed by rotifers ( Brachionus plicatilis), Artemia nauplii, copepods and finally weaned onto a zein micro-coated diet. Metamorphosis started when larvae reached 9.7 mm TL at 30 days of age, and was complete by Day 38 when larvae were 12.4 mm TL. From Day 20 after hatching, the larger larvae (7 mm TL) began to exhibit agonistic behavior. Intestinal swelling was frequently observed in larvae at 22–25 days after hatching (5–8 mm TL). p ]Two types of skeletal malformations, lordosis (10–21%) and brachyospondyliosis (1–4%), were frequently observed in the juvenile stage. Initial larval stocking densities were inversely correlated with survival ( r = −0.80, P < 0.01). Optimal initial stocking density was 10–15 larvae 1 −1. Larval rearing trials for growth and survival to 50– 56 days produced juveniles of 20 mm average total length, at a survival rate ranging from 0.7 to 27.5%.