Ecological knowledge of oyster (Crassostrea) collectors on abiotic aspects: Implications for co-management

Oysters of the Crassostrea genus (Sacco 1897) are commercially and ecologically important species that inhabit coastal and estuarine waters. However, exploitation without proper species management can contribute to declining natural stocks, especially in regions with easy access. In this sense, the objective of this study was to analyze the local ecological knowledge (LEK) of the collectors about the biometry of Crassostrea rhizophorae and Crassostrea brasiliana oysters collected during the seasonal periods (dry and rainy) in the Mamanguape River Estuary (MRE) and the stock conditions of this resource in order to provide information to complement the EPA management plan of Barra do Rio Mamanguape on the northern coast of the state of Paraíba, Brazil. The study was conducted between August 2019 and September 2020 through semi-structured interviews, participant observations, and meteorological data. The results showed the occurrence of oysters (C. rhizophorae and C. brasiliana) popularly named mangrove and bottom oysters, respectively. They were identified according to morphological and ecological characteristics and classified into different size groups. The biometry of the species varies according to the seasonal period; the oysters present a variation between 50-80 mm during the dry period, being larger than in the rainy period which presented a variation of 40-70 mm. In addition, collectors reported that there has been a decrease in stocks and the size of oysters collected over the last decade. According to this information, there is a threat to the sustainability of fishing in the MRE in the medium and long term. Thus, it is necessary to involve the local community in negotiations in defining and distributing management functions, rights, and responsibilities to maintain the livelihoods of MRE collectors and increase oyster stocks.