Reproductive cycle of Crassostrea gasar cultivated in three different locations at the Estuarine Complex of Paranaguá (PR)

Abstract The reproductive cycle is an essential aspect of oyster farming. Understanding the period of each sexual stage aids in planning oyster harvest, seed collection with artificial collectors, and reproductive season for hatchery seed production. In this sense, this work evaluated the reproductive cycle of Crassostrea gasar oysters cultivated in three important oyster farming locations in the Estuarine Complex of Paranaguá, Rasa Island, Medeiros, and Ponta Oeste (Mel Island), with monthly oyster sampling in each sampling site. Temperature and salinity were recorded in loco at each sampling time. In the laboratory, oysters were identified and measured; tissue samples were collected for molecular identification of species; and histology was conducted for reproductive cycle analysis. Histological examination of the gonadal tissue was performed with slides stained with Harris hematoxylin and eosin. Salinity and temperature data showed no differences between the three sampling sites during the studied period. Molecular analysis showed that the oysters sampled were C. gasar (100%). Histological analysis showed intense spawning of C. gasar in December and February (26.72 °C) and June (20 °C). There was a resting stage in both males and females during winter. Some oysters (n = 21) were parasitized by Bucephalus sp., and it was impossible to determine oyster sex.