Diet and population biology of the invasive crab Charybdis hellerii in southwestern Atlantic waters

Abstract

For many species the population structure varies along latitudinal gradients, especially at the extremes of their distributions. This may apply to invasive species, whose ability to grow, reproduce, feed and compete is hypothesized to be lower at higher latitudes. A population of Charybdis hellerii was investigated on a rocky shore at Armação do Itapocoroy (Santa Catarina, 26°40′–26°47′S and 48°36′–48°38′W), Brazil. The study was carried out over two periods to test the hypotheses that: (1) this population differs from other populations that presumably became established earlier and at lower latitudes; (2) the population parameters change over time (number and size of individuals and ovigerous females), progressively showing more indications of establishment; and (3) the diet overlaps with the native crabs. In total, 642 individuals were caught: 544 males, 55 females, and 43 ovigerous females. This population of C. hellerii is similar to others presumably established earlier and at lower latitudes on the Atlantic coast, with a predominance of larger males and a male-biased sex ratio. The population is reproducing, but the similarity in the population size and frequency of ovigerous females between periods may indicate that this population is encountering difficulty in increasing in size. The generalist diet was composed mainly of crustaceans, molluscs and algae, thus overlapping with other native crab species. Although the direct and indirect impacts of this invasive species were not assessed, the population parameters indicate that this population of C. hellerii is established and may act as a centre of dispersal to higher latitudes.