Effects of salinity on the juvenile crab physiology and agonistic interactions between two species of blue crabs, Callinectes sapidus and C. similis from coastal Louisiana

Callinectes sapidus and Callinectes similis are found in estuaries along the northern Gulf of Mexico. Juvenile C. sapidus are heavier at similar carapace widths than juvenile C. similis. Juvenile C. sapidus and C. similis exhibit similar patterns of hemolymph osmolality, oxygen consumption, lactic acid concentration, and renal filtration and secretory rates along constant and fluctuating salinity gradients. When similar sized juveniles were present, significantly more C. sapidus were preyed upon at 30 PSU but not at 5 PSU. Juvenile C. similis are more vulnerable to predation by adult C. sapidus at low salinity, this increased predation by adult C. sapidus on juvenile C. similis at 5 PSU may contribute to limiting the presence of C. similis to higher salinity water along estuarine gradients.