Behavioral ecology and population biology in populations of fiddler crabs, Uca pugnax (Smith), on the New Jersey Coast

The constant addition of anthropogenic pollutants into estuarine waters has elicited a concern for organisms within this complex habitat. Fiddler crabs, Uca pugnax, were collected from several sites along the New Jersey Coast to determine if and how environments with varying levels of pollutants might impact aspects of behavioral ecology, metal storage and depuration, and population biology.;Behavioral observations revealed no aberrant behaviors in crabs from a highly contaminated site. However, at the most contaminated site decreased foraging time and more time spent in burrows, possibly related to higher nutrients, was found. Activity was also affected by weather. Developing a tolerance combined with the nutrient rich environment may enable this species to thrive in contaminated marsh ecosystems.;Metal distributions in the exoskeleton and soft tissues during intermolt and immediate post-molt revealed that crabs from the highly contaminated site had significantly higher concentrations and they depurated a significant amount of lead and mercury. The proportions (soft tissues/exoskeleton) vary with metal type and changes between intermolt and molt phases. Crabs from the cleaner site shifted all metal types into the soft tissue prior to molting. In contrast, crabs from the contaminated site shifted non-essential elements (Cd, Pb, Hg) into their exoskeleton prior to molting. However, molting reduced overall body burdens significantly and is a feasible mechanism to depurate non-essential metals in both populations.;Investigation of population parameters showed that crabs from the highly contaminated site were significantly larger in size, but had lower population density, lower recruitment, shorter reproductive season and lower survivorship of early benthic phases. This study also determined that the reproductive season for Uca pugnax in New Jersey is longer than previously reported and may reflect of climate changes.;This study suggests that fiddler crab population density may be reduced due to contamination. However, tolerance may develop through mechanisms such as depurating toxicants via molting. Consequently, the usefulness (or sensitivity) of behavioral observations to assess the effect of contaminants may be limited once mechanisms have developed to compensate for toxicants.