Seasonal steroid variations in relation to maturity stages in the female Pacific red snapper Lutjanus peru in the Gulf of California, Mexico

Abstract

Reproductive steroid concentration and gonadal development as well as plasma cortisol were investigated during the reproductive period (April to October) of the Pacific red snapper Lutjanus peru, a commercial and important local fishery species in the surrounding areas of Bahía La Paz, Gulf of California, Mexico. Gonads in April were immature and characterized by the presence of oocytes at the chromatin nucleolar and perinucleolar stages. In the next month, more than 50% of the fish showed gonads in vitellogenesis, characterized by the presence of cortical alveoli and early vitellogenic (V1) oocytes. Late vitellogenic and mature gonads were present in July, August and September. Postovulatory follicles were observed only in gonads collected in August, indicating spawning activity of these individuals. The gonadosomatic index (GSI) increased significantly (p <0.05) from April and May to July, when it reached its maximum value. A significant increase (p <0.05) in plasma testosterone (T) was also observed in July compared to previous months, and plasma estradiol (E2) concentration was significantly higher (p <0.05) in September than in April. Cortisol concentration was significantly higher (p <0.05) in September than in May. Significant differences (p <0.05) between gonadal stages were observed for GSI and E2 but not for T. We conclude that the Pacific red snapper, in the surrounding areas of Bahía de la Paz, showed an asynchronous ovarian growth starting in May when water temperature increased and that was characterized by several spawning events.