Diversidade e abundância de moluscos bivalves na zona entremarés em duas áreas na Ilha de Inhaca, sul de Moçambique

Abstract

Bivalve mollusks are important fishery resources for the communities of Inhaca Island, as they contribute to food security and generate significant income. Their intensive exploitation makes it essential to understand diversity and abundance in order to assess population dynamics and support management measures aimed at conservation and sustainable use. This study aimed to analyze the diversity and abundance of bivalve mollusks in the intertidal zone of two areas of Inhaca Island, namely EBMI and Ponta Ponduíne, in southern Mozambique. Sampling was conducted in October 2023 over seven days of spring tide, using transects placed perpendicular to the shoreline, with systematic placement of quadrats (0.5 × 0.5 m) along them. A total of 9 families, 12 species, and 3,037 individuals were identified in EBMI, and 7 families, 11 species, and 11,623 individuals in Ponta Ponduíne, totaling approximately 14,660 individuals across both areas. In EBMI, the family Ostreidae (Saccostrea cuccullata) was the most abundant, followed by Mytilidae, Veneridae, and Donacidae. In Ponta Ponduíne, Ostreidae dominance was even more pronounced, while the other families showed relatively lower abundances, with Veneridae, Mytilidae, and Arcidae standing out. EBMI exhibited greater family diversity, although Ponta Ponduíne presented a higher total abundance of individuals. Regarding diversity indices, EBMI recorded higher values (Shannon H’ = 2.7; Simpson D = 0.74), whereas Ponta Ponduíne showed lower diversity (Shannon H’ = 1.3; Simpson D = 0.37). The most abundant species in both areas were: Donax faba (54 ± 18 ind./m²), Modiolus philippinarum (45 ± 5 ind./m²), Semele radiata (45 ± 12 ind./m²), Trachycardium rubicundum (50 ± 4 ind./m²), Saccostrea cuccullata (102 ± 29 ind./m²), Mactra liliacea (42 ± 7 ind./m²), Eumarcia paupercula (24 ± 8 ind./m²), and Perna perna (44 ± 10 ind./m²). The Kruskal–Wallis test revealed statistically significant differences in species abundance in both areas (EBMI: H = 50.47; p = 0.05; Ponta Ponduíne: H = 71.53; p = 0.05). In both sites, Saccostrea cuccullata stood out with significantly higher abundance compared to several other species, confirming its dominant role in the community. These results demonstrate heterogeneity in species composition and suggest that local environmental factors favor certain species over others.