Population ecology of the hermit crab Clibanarius symmetricus (Anomura: Diogenidae) on an exposed beach of the Brazilian Amazon coast

The hermit crab Clibanarius symmetricus is a conspicuous species in the intertidal zone of several environments along the Western Atlantic. Low salinity has been suggested as a major factor that affects the population structure of C. symmetricus, causing absence/scarcity of ovigerous females and juveniles. The marked seasonal variation in rainfall provides the opportunity to assess salinity-related patterns of temporal density, and population dynamics (growth, mortality, and secondary production) of C. symmetricus in a low rocky outcrop of an equatorial exposed dissipative sandy beach. The results showed that C. symmetricus density reached high values (∼25 ind. m−2) and increased with increasing salinity. As opposed to previous studies, our data indicate that salinity did not inhibit the simultaneous presence of age and sex categories. The constant presence of ovigerous females and juveniles indicated continuous reproduction. The larger size of males compared to females was due to their lower mortality and longer life span. The high production-to-biomass ratio (P/B = 2.44 year−1) indicates a rapid biomass replacement for this equatorial population. Shelter provided by the rocky outcrop on this exposed dissipative beach is a key factor in the success of this population. These data are relevant to build a general overview of C. symmetricus life history traits, since knowledge of this species is generally limited to subtropical populations. •Density of Clibanarius symmetricus increased with increasing salinity.•Males were larger than females due to their lower mortality and longer life span.•High P/B indicates a rapid biomass replacement for this equatorial population.