Blue Crabs can be found in brackish water too. When I was younger my friend and I would "fish" for them. His parents would get scrap chicken necks from the grocery store. We would tie the chicken to a rope and drop it off a dock on the Estero River here in FL. The crabs would swarm the chicken and we would just scoop them up with a net. Man they were good eat'n!
PS they can also be sexed by the shape of their abdomen. Males have a "T" shape, like a phallus. Females are a rounded off, triangular shape.