Population dynamics of Brachidontes darwinianus (Mytilidae) occurring in sympatry with the invasive Mytilopsis leucophaeata (Dreissenidae) in a coastal lagoon (Rio de Janeiro, Brazil)

The native bivalve Brachidontes darwinianus occurs in sympatry with the invasive bivalve Mytilopsis leucophaeata in Rodrigo de Freitas Lagoon, an urban coastal lagoon located in the city of Rio de Janeiro, Brazil. Both species are found in hard substrates and form clusters around the lagoon. This study aimed to evaluate the population aspects, such as growth and mortality rates, of the native bivalve B. darwinianus and compare with data available for M. leucophaeata for this lagoon. Population data were analyzed and compared between bivalve species over two years: 2016-2017 and 2017-2018. In both years, the growth rate of B. darwinianus remained similar (K = 0.5), while the mortality rate showed a slight increase in the second year (Z2016-2017 = 2.25; Z2017-2018 = 2.9). The densities of M. leucophaeata were significantly higher than those of B. darwinianus regardless of the year analyzed. However, an increasing trend in the densities of the native bivalve was observed in the second year, suggesting a coexistence of native and invasive bivalves in the lagoon. Therefore, more studies are needed to understand the ecological interactions between these species, given that the invasive bivalve is established and can induce changes in the benthic community of this environment.