Involvement of brain-pituitary-gonadal axis on regulation of the reproductive cycle in female chub mackerel

The chub mackerel (Scomber japonicus) is one of the commercially important marine pelagic fishery resources of the world, and aquaculture of this species commenced recently in Japan. Captive maintained male fish undergo normal spermatogenesis but female fish after the completion of vitellogenesis fails to undergo final oocyte maturation and ovulation. The Brain-Pituitary-Gonadal (BPG) axis is an indispensable neuroendocrine pathway shown to be involved in the regulation of reproductive cycle of teleosts and understanding their involvement is important for aquaculture and stock management of chub mackerel. This chapter introduces the importance of chub mackerel as an experimental animal and the experimental system, followed by the characterization and analyses of hormonal players of BPG axis namely, kisspeptins, gonadotropinreleasing hormones (GnRHs), gonadotropins (GtHs) and sex steroids during the reproductive cycle.