Reproductive Cycle, Spawning, and Fecundity of Sebastes oculatus (Patagonian Redfish) in the Argentine Continental Shelf

The Patagonian Redfish ( Sebastes oculatus ) is a viviparous species that inhabits the mid and outer shelf waters and rocky reefs off the Patagonian coast of Argentina where two morphotypes have been identified: the “dark” or “shallow” (mostly <30 m depth) and the “light” or “deep” (>80 m depth). Information on the reproductive biology of the “light” morphotype is scarce, so the main objectives are to describe the gonadal maturation phases and to determine the oocyte growth pattern of the species in deeper waters. In addition, we analyze the annual cycle of gonadal and liver condition indices in relation to sexual maturity and provide a preliminary estimate of potential fecundity. Samples were collected on commercial vessels by on-board observers between November 2016 and October 2017. The pattern of oocyte development showed that S. oculatus is a group-synchronous species, with gonad development beginning in the late austral winter and continuing into the spring, while larval emergence occurs in spring and early summer. Males mature before females, so copulation may occur in the fall, and females would retain sperm in the ovary until oocyte fertilization. The evidence suggests that viviparity of this species is lecithotrophic, and positive relationships have been found between relative fecundity with maternal size, which indicate that larger and older females have greater reproductive potential (producing more eggs than younger individuals).