Population biology of the freshwater crab Dilocarcinus pagei Stimpson, 1861 (Decapoda: Trichodactylidae) in the Araguari River, south-eastern Brazil

Dilocarcinus pagei is a freshwater crab that has a wide distribution in South America, occurring in the main river basins of Brazil. Our study analysed some aspects of the population biology of D. pagei in a population that occurs in the Araguari River, in south-eastern Brazil. Crabs were sampled between September 2020 and November 2021. The population structure was analysed according to the organisms’ size, sex and life stage. The frequency of demographic groups (adults and juveniles) over months was assessed using an environmental gradient analysis and a canonical correspondence analysis (CCA). A total of 392 crabs were collected, 282 males and 110 females. Male crabs were more abundant during most of the sampling period. Thus, the sex ratio in general and for most months was biased towards males. Gradient and CCA analyses showed seasonality in the occurrence of ovigerous females. This demographic group was more frequently sampled when the local rainfall increased. Our study provides relevant information about the population and reproductive biology of D. pagei, which may contribute to the understanding of the reproductive traits of freshwater crabs and also the ecological role of this species in the environments it inhabits.