Hormonal profiles and reproductive development of hatchery-reared first filial (F1) generation silver trevally (Pseudocaranx georgianus, Carangidae)

We examined the annual (maiden) reproductive cycle of hatchery-reared first filial (F1) generation silver trevally (Pseudocaranx georgianus) by tracking ovarian development and plasma levels of follicle-stimulating hormone (Fsh), luteinizing hormone (Lh), and estradiol-17β (E2). Our aims were to determine the age at puberty, identify reproductive dysfunctions, and lay the groundwork for manipulating the spawning season. To achieve this, mixed-sex two-year-old fish (n = 424) were maintained in a 13-m 3 tank under ambient conditions. Baseline samples were collected in April 2018, followed by near-monthly sampling (every 4–6 weeks) from July 2018 to April 2019. Puberty occurred at 3 years of age. Fish showed distinct seasonality in their reproductive cycle, with a clear peak in activity during the months of November to December (late spring/early summer). Reproductive development in females was limited, with only 2.7 % out of 113 females sampled achieving late vitellogenesis, and no instances of oocyte maturation or spontaneous spawning were observed. Contrary to increasing plasma E2 content as oogenesis progressed, plasma concentrations of Lh and Fsh remained relatively stable across oogenesis stages. The lack of increased plasma Lh suggests that reproductive dysfunction (absence of spontaneous spawning) may be due to insufficient quantities of Lh being released into the bloodstream to accomplish oocyte maturation, ovulation and spawning. Puberty of hatchery-reared F1 silver trevally first occurred at 3 years of age. The percentage of females achieving late vitellogenesis was low. A high percentage of females with oocyte atresia was observed. No spontaneous spawning was observed.