Diversidade, abundância de moluscos bivalves e sua exploraçao na praia do bairro dos Pescadores, baía de Maputo

Abstract

Bivalve harvesting during low tide is a common activity at Praia do Bairro dos Pescadores, in Maputo Bay, and is important for the livelihood of vulnerable populations, as these molluscs are used as food by many families in the coastal region. This study assessed the diversity, abundance, biomass and size structure of bivalves in the intertidal zone at Praia do Bairro dos Pescadores in April and May 2022. Samples were obtained from 60 grids distributed in 12 transects perpendicular to the coastline. A total of 491 individuals of 10 bivalve species were collected, distributed among 6 families. Meretrix meretrix (30% of individuals) followed by Macra lilácea (21% of individuals) were the most abundant species, Perna viridis (15% of individuals), Macra cuneata (12% of individuals), Tapes literatus and Eumarcia paupercula (9% of individuals), Solen cylindraceus (2% of individuals), Semele radiata (2% of individuals). Solen roseamaclatus and Tellinu foliacea were the least abundant. The average densities of the species followed the same pattern of numbers of individuals. The highest density of bivalves was found in the substrate with seagrass, compared to the muddy, mud with stones and sandy substrates. All species presented in their composition of sizes small and immature individuals, mature/adult individuals were only found in the species of Tapes literatus suggesting a high level of human exploitation. The highest biomasses were presented by the species Meretrix meretrix, Macra lilácea and Macra cuneata, respectively. The species with moderate biomass were Tapes literatus and Eumarcia paupercula, while the remaining species had lower biomasses. The allometric relationships between fresh weight and lengths were positive and significant for 9 of the 10 bivalve species. The morphometric relationship for Semele radiata was not calculated due to the insufficient sample size. Bivalves, especially the species Meretrix meretrix, are exploited mainly by adult female collectors, mainly residents of Bairro dos Pescadores, the majority of whom are women who use hoes. The clams are harvested for consumption (food). The quantities collected varied from 0.6 kg/day to 20 kg/day, with an average of 6.55 kg/day (standard deviation of 3.828 kg/day). The collectors’ perception is that catch levels are decreasing. This study can serve as a baseline for monitoring bivalves harvested at Praia dos Pescadores(TRADUÇÃO NOSSA)