If you’re curious about blue crabs and live either near the Delaware Bay or Delaware’s Inland Bays, then you may be interested in volunteering to help marine scientists at the University of Delaware’s College of Marine Studies. The scientists are working to understand the population dynamics of the Atlantic blue crab, Callinectes sapidus. All equipment and training will be provided, and a minimum of time is required.
The blue crab, found from Nova Scotia through the East and gulf coasts of the United States and into the West Indies, is one of the most important fisheries in the Delaware Bay. However, year-to-year fluctuations in blue crab catches have heightened concerns that the crab population is declining in the area.
Not surprisingly, the size of the blue crab population in any given year partially depends on the size of the population of juvenile blue crabs. UD scientists, in a project funded by the Delaware Sea Grant College Program, have developed a mathematical model for predicting variations in the juvenile population over time. This model will assist management officials protect the fishery by helping to prevent over fishing.
According to Charles Epifanio, professor of marine biology-biochemistry and principal investigator of the project, the model has been successful in predicting general trends in recruitment of young crabs to the adult population, but has not been able to provide detailed information about year-to-year variation in recruitment. Epifanio believes that detailed predictions will require a more extensive data set concerning patterns of egg hatching in the species.
“Our model is likely to provide a unique new tool for management of the fisher,” says Epifanio. “However, one key piece of the puzzle — a detailed understanding of the pattern of egg hatching during the spawning season — is missing. The involvement of volunteers at this point is critical to coming up with that missing piece.”
The volunteers will assist in collecting “sponge crabs,” or female crabs that are carrying eggs, and remove a small sample from the sponge, or egg mass. Once the egg sample has been taken, the crab will be returned to the water. Epifanio notes that the crabs are not harmed in this process. The scientists will analyze the egg samples to predict the day on which the eggs will hatch. This information will then be entered into the mathematical model to help determine the size of the juvenile population.
During the night, crabs will be collected at high tide from the fishing pier in Cape Henlopen State Park. These collections will be done seven nights a week from mid-June through September by dipping a net into the surface of the water. Volunteers can collect crabs for as little as one night a week, and the process takes approximately two hours.
Another type of net, called a beach seine, will be used to collect crabs at Lewes Beach during the day. These collections will be done twice a week at low tide. Volunteers can collect crabs for as little as one day a week and the process takes approximately three hours.
Please call the College of Marine Studies at (302) 645-4279 for more information or to learn how you can volunteer.