CANNIBALISM, REFUGIA AND THE MOLTING BLUE-CRAB

In this study, we examined how habitat and tidal stage influence preda tion upon molting blue crabs Callinectes sapidus. On 3 separate occasi ons we monitored the survival of tethered soft crabs in each of 2 diff erent-sized marsh creeks and 2 seagrass sites, during both low and hig h tides. On one of these occasions, we also tethered hard crabs. Survi val was much lower for soft crabs than for hard crabs, indicating that crabs may be particularly vulnerable when they molt. In both seagrass and marsh creeks, there was a tidal influence upon soft crab survival , with greater survival during low tides. There was no generalized dif ference in survival of soft crabs between habitats, i.e. marsh creek v ersus grassbed. Survival was high in the small marsh creek, but lower in the large marsh creek. In both creeks survival remained relatively constant throughout the summer. In contrast, survival did not differ b etween the 2 seagrass sites and was comparable to that in the small ma rsh creek early in the summer, but decreased to levels comparable to t he large marsh creek by summers end. In the marsh creek, micro-habitat also influenced survival, with greater survival along the creek edge micro-habitats than in the creek centers. Cannibalism was the only ide ntifiable source of mortality among tethered crabs. These results demo nstrate that where and when a crab molts may greatly influence its cha nces for survival.