Hormone-induced ovulation, natural spawning and larviculture of Brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839)

Abstract

Mature Brazilian flounders Paralichthys orbignyanus were captured in coastal southern Brazil and their reproduction in captivity was studied. Brazilian flounder will spawn naturally in captivity when the water temperature is around 23 1Cand14hof light is provided daily. Females were induced for ovulation and hand stripping using human chorionic gonadotropin, luteinizing hormone-releasing hormone analogue or carp pituitary extract. There was no need to inject males, as running milt was observed during the spawning season. Fertilization and hatching rates were above 80% independent of the hormone used. Notochord length at hatching was 2.18 _ 0.07mm for larvae hatching from naturally spawned eggs. Larvae were reared in salt water (30^35 g L_1) at 24 1C and under continuous illumination. Larviculture was with green water (Tetraselmis tetrathele 50 _ 104 cellsmL_1). Rotifers (10^20 indmL_1) were o!ered as ￠rst food 3 days after hatching and gradually replaced by Artemia nauplii (0.5^ 10 ind mL_1). Larvae settled to the bottom 20 days after hatching and completed metamorphosis within a week after that. The total length for newly metamorphosed juveniles was 12.9 _ 2.2mm and the mean survival was 44.8%. The results demonstrate the feasibility of producing Brazilian flounder￠ngerlings for stock enhancement or grow-out purposes.