Raising Blue Crabs in Freshwater
Researchers at North Carolina State University may have found a solution. Dr. Dave Eggleston, director of North Carolina State's Center for Marine Sciences and Technology (CMAST) and professor of marine, earth and atmospheric sciences, looked at various methods for helping the population recover. He found a potential solution that reduces pressure on existing crab populations, and also benefits farmers looking to diversify their crops: using irrigation ponds on farms to grow blue crabs.
"We started out by catching small crabs in the wild and stocking them into farm ponds loaded with bass and bluegill predators, and were still able to get 12 percent survival," Eggleston says. "So we teamed with the University of Maryland's Center of Marine Biotechnology who had the expertise to growth hatchery-reared blue crabs, and stocked these blue crabs in freshwater experimental aquaculture ponds at North Carolina State's Vernon James Research and Extension Center in Plymouth, N.C., where the crabs exhibited some of the highest growth rates on record."
The critical piece was to see if crabs could live in irrigation ponds that are mostly freshwater. Eggleston and his researchers discovered that crabs can tolerate a salinity level of only .3 parts per thousand, about the same level found in coastal tap water. They next researched the best set of circumstances for raising crab: population density, food rations, and habitat structure in ponds.
This past July, Eggleston and Ray Harris, North Carolina State director of cooperative extension for Carteret County, conducted a large-scale test where they stocked a 10-acre lake with 40,000 hatchery-raised crabs, and a smaller pond with 4,000 crabs. The crabs take roughly 105 days to reach maturity and so far the endeavor looks successful. Eggleston expects that in a given year, a farm could produce two to three harvests, since crabs don't do well in freshwater during the winter months.