Seasonal and spatial changes in sex hormone levels and oocyte development of bonefish (Albula vulpes)

Bonefish (Albula vulpes) support an economically important fishery, yet little is known regarding the reproductive biology of this species. Blood and oocyte samples were collected from wild female bonefish (Albula vulpes) during (February and April, 2017) and outside (September, 2017) the spawning season in Grand Bahama Island, The Bahamas. Fish reproductive state was evaluated using histological analysis of the oocytes and determination of sex hormone levels of 17β-estradiol and testosterone in the plasma. The presence of three different cohorts of oocytes in bonefish females suggests group-synchronous ovarian development. Levels of 17β-estradiol were low in individuals sampled outside of the spawning season relative to fish sampled during spawning months. Testosterone levels did not change as female bonefish entered the spawning season. Within the spawning season, bonefish are commonly found along shallow water flats, or in pre-spawn aggregations (PSA). The diameters of late vitellogenic oocytes collected from PSA fish were significantly larger than those from the flats fish. Levels of 17β-estradiol did not differ between PSA and flats fish; however, testosterone levels were significantly higher in fish from the PSA. These results indicate that as bonefish are transitioning to the PSA from flats habitats, vitellogenesis is still occurring. However, when and where final maturation commences in reproductively active bonefish remains unclear.