Population dynamics of Parhyale hawaiensis (Dana, 1853) (Amphipoda: Hyalidae) associated with an intertidal algal belt in southeastern Brazil

Static life tables were used to establish demographic parameters such as size-class structure, abundance trends, sex ratio, net reproductive rate, generation time, and per capita rate of population growth for a population of the amphipod Parahyale hawaiensis (Dana, 1853) (Hyalidae) from the intertidal belt of a red alga Bryocladia trysigera (J. Agardh) F. Schmitz in southeastern Brazil. Collections were taken monthly from December 2012 to November 2013. There were two reproductive peaks, a higher one, May to July, and a second throughout the warmer months, October to January. The continuous reproduction results in the overlapping of generations. A sex ratio biased in favor of females was recorded in all sampling dates, a common pattern in epifaunal species. The estimated net reproductive rate was 1.45 ± 1.01 young per female, the generation time 3.51 ± 1.31 months, and the population growth rate 0.06 ± 0.17 per capita per month. The logistic growth model indicates that an initial population of 10 individuals would reach the carrying capacity for the species in a natural environment in 35 to 40 generations time, a period equivalent to 130 to 150 months. As a result of extinction model application, no possibility of extinction was predicted for the local population. The estimated parameters can be used as endpoints in ecotoxicological tests.