Abstract: Blue crabs (Callinectes sapidus) were collected from two sites in NJ: Hackensack Meadowlands (HM), and Tuckerton (TK). Differences were found in juvenile predator avoidance ability and adult prey capture in laboratory studies. HM juveniles were significantly better at avoiding an adult crab predator than TK juveniles. HM adults were less efficient at capturing juvenile crabs but were comparable predators on fiddler crabs (Uca pugnax) and ribbed mussels (Guekensia demissa). Stomach analysis shows HM adults eat less nutritious food (less live prey and more sediment and detritus) than TK adults, but surprisingly no detrimental impacts were observed in the HM population; they seem to be larger than TK crabs in both population and body size. This may be a result of reduced fishing pressure at HM where there is a fishing advisory. Increment at molt of crabs from both populations was comparable. However, lipofuscin analysis indicates that HM crabs of a given size may be younger suggesting that they could be molting more often. Genetic studies indicated no differences among populations. To examine the effect of the environment on behavioral differences observed in the lab, crabs from each population were caged in the other site as well as their native site as a control. Data indicate TK crabs placed in HM became less efficient predators; simultaneously, HM crabs placed in TK became more efficient predators than HM controls. This indicates that environmental conditions in HM (contaminants) are primarily responsible for the impaired behavior of the blue crabs.