Ecology of Callinectes arcuatus and C. bellicosus (Decapoda, Portunidae) in a coastal lagoon of northwest Mexico

Some ecological aspects of the swimming crabs, Callinectes arcuatus and C. bellicosus are presented. Specimens were collected with a trawl net, both day and night, on a monthly basis from March 1998 to February 2000 in a coastal lagoon in northwest Mexico. A total of 1235 specimens were captured, C. bellicosus (n = 878) (abundance 0.5 to 60 ind. ha^-1) was more abundant than C. arcuatus (n = 357) with an abundance from 0 to 38 ind. ha^-1 during the study period. Both species were more abundant at night and usually were found in conjunction with macroalgae. Salinity (32 to 40‰) tended to favour the dominance of C. bellicosus over C. arcuatus (2.4 : 1) and the water temperature appeared to govern the breeding season (21 to 32°C). For both species, the breeding season runs from March until September (spring-summer), the recruitment of juveniles occurs during January and February (winter), and the lowest abundance of both species is found during October and November (fall). For both species, ovigerous females were observed in the mouth of the lagoon, and juveniles were found in the lagoon's interior parts. The authors think that the observed ecological patterns of the species could be extrapolated to other coastal lagoons with a similar climate, oceanography, and geomorphology.