No abstract

At midlatitudes within its range, overwintering mortality may play an important role in regulating blue crab (Callinectes sapidus) populations. We conducted a 121-day experiment to estimate winter mortality that used realistic temperature acclimation periods prior to and light levels during experiments. A 2 × 2 × 2 factorial experimental design was used to test for the effects of temperature (3°C, 5°C), salinity (10, 25), and sediment (sediment, no sediment) on the survival of juvenile crabs (14-68-mm carapace width) of both hatchery and wild origin. The presence of sediment did not significantly alter crab survival, while hatchery-raised crabs experienced significantly lower survivorship than wild-caught crabs. An accelerated failure time model fit to the survival data indicated that time to death increased significantly with increasing temperature, salinity, and crab size. These results suggest that winter survival varies with winter severity, is spatially dynamic, and that small juveniles are more at risk of dying over the winter than larger juveniles.

We present a 2-stage generalized additive model (GAM) of the distribution of mature female blue crab Callinectes sapidus in Chesapeake Bay based on data from a fishery-independent winter dredge survey. The distribution and abundance of blue crabs was modeled as a flexible function of depth, salinity, water temperature, distance from the Bay mouth, distance from submerged aquatic vegetation (SAV), and bottom slope for each of the 13 yr of data available. Depth, salinity, temperature, and distance from the Bay mouth were found to be the most important environmental determinants of mature female blue crab distributions. The response curves for these variables displayed patterns that are consistent with laboratory and field studies of blue crab/habitat relationships. The generality of the habitat models was assessed using intra-and inter-annual cross-validation. Although the models generally performed well in cross-validation, some years showed unique habitat relationships that were not well predicted by models from other years. Such variability may be overlooked in habitat suitability models derived from data collected over short time periods.KEY WORDS: Blue crab · Chesapeake Bay · GAM · Cross-validation · Habitat suitability model Resale or republication not permitted without written consent of the publisher