Changes in sex steroid hormone levels reflect the reproductive status of captive female zebra sharks (Stegostoma fasciatum).

•The Zebra shark showed an annual reproductive cycle.•E2 tended to increase a couple of months before ovarian follicle development.•E2 decreased along with the follicle depression.•Changes in E2 were inversely correlated with water temperature.•High levels of testosterone were correlated with the egg-laying period.