Although we do not yet know for certain why the abundance of crabs is so low this summer, evidence suggests it is due to low numbers of reproductive females during the summer 2012 spawning season. In 2008, new protections on harvesting adult female blue crabs were enacted, which has led to higher numbers of female blue crabs in four of the five years since (according the Winter Dredge Survey). However, the winter of 2012 was the one year in which the number of spawning-age females was very low. With few females in winter 2012, it is likely that reproduction was also very low in the summer of 2012. Our survey is designed to target crabs that are roughly one year old. Because of this, it appears likely that the low number of crabs caught in our survey (and in the 2013 Winter Dredge Survey) was the result of low reproduction in summer 2012. Other factors such as weather, harvest, predation, habitat loss or water quality could also have played a role.
While it is yet unknown exactly why there was a low number of female blue crabs found in the 2012 Winter Dredge Survey, the relatively high number of females in four of five years since 2008 suggests that the protections placed on female blue crabs are working. Long-term monitoring data from SERC’s summer crab survey, the Winter Dredge Survey and other sampling programs show that protecting the population of adult females is one way to ensure that the blue crab, an important ecological and commercial species, remains abundant throughout the Chesapeake Bay.