Hormonal treatments for induction of oocyte maturation and ovulation in wild Japanese sea bass, Lateolabrax japonicus

It is very important to develop efficient and stable techniques for obtaini ng fertilized eggs with goad quality as well as sufficient quantity, partic ularly for difficult species as Japanese Sea Bass. Effects of a single horm one or combined hormone treatments on induction of oocyte maturation and ov ulation were examined in wild Japanese Sea Bass which were collected by lon glines near the coast of Kujukuri in Chiba Prefecture during spawning seaso n in 1989 and 1990. The present data were evaluated by comparison with prev ious data obtained from 1982 through 1988. HCG (human chorionic gonadotropi n) from 1982-1990, SP (silver carp pituitary extract) in 1989 and CP (chum salmon pituitary extract) in 1990 were used in the respective experiments. HCG-SP group produced viable eggs by artificial insemination. Spontaneous s pawning in tanks was induced by HCG-SP and SP treatments, but the number of eggs uas evidently larger in HCG-SP group. HCG-CP treatment was more effec tive than HCG-SP treatment in 1989. The number of floating viable eggs and hatched larvae induced by the combined hormone (HCG and pituitary extracts) treatment appeared to be greater than those obtained by a single hormone t reatment conducted from 1982 through 1988. These results suggest that the c ombined hormone treatment is effective in inducing ovulation for Japanese S ea Bass.