Agonists of gonadotropin releasing hormone (GnRHa) pellets implantation in Seriola dumerili (Risso, 1810) under water temperature variations

The aim of the present study was to enhance the current knowledge on reproduction of Mediterranean greater amberjack (Seriola dumerili) in aquaculture and evaluate the influence of temperature variations on the sexual cycle. Fifteen Seriola dumerili (6 males and 9 females) were enrolled in the study. The animals were randomly divided in two groups: experimental group (n = 8) and control group (n = 7). Before experimental trial starts, biopsies from each fish were performed in order to establish gonadal maturation state. Afterwards, spawning was stimulated in experimental group through the agonists of gonadotropin releasing hormone (GnRHa) implants. No spawning events were observed in experimental group neither in control group during the week after experimental trial. The water temperature control showed a variation of about two degrees between the fourth and the sixth day after implantation. A week after experiment, a second gonadal biopsy was executed showing a gonadal regression in female subjects of both groups and an increase in sperm production of male subjects of experimental group. The study underlines the influence of water temperature variation on fish reproduction, in particular in females, even if GnRHa implants were used to stimulate spawning.