Blue Crab Abundance


Blue crabs are an important food source for over-wintering whooping cranes at Aransas National Wildlife Refuge.

The blue crab (Callinectes sapidus) is a species of crab native to the western Atlantic Ocean and the Gulf of Mexico. In this part of the Gulf of Mexico, females migrate to areas of high salinity where their eggs can be fertilized by sperm they have previously stored. Up to two million eggs can be produced from one brood, and a single female can produce more than 8,000,000 eggs in her lifetime.

After the eggs are fertilized, the female broods them in a sponge on her belly for about two weeks. In late fall she releases the eggs which hatch into planktonic larvae and float freely for about five weeks. Juvenile crabs then make their way back into the marshes where they can grow to about 9 inches from spine tip to spine tip.

In south Texas, blue crab can be found in the salt marshes and open bays, but their abundance and availability to whooping cranes fluctuates. From a management perspective, understanding the relationship between crane survival and productivity and the abundance of blue crabs is important.

To gain insight into this relationship, the refuge has been studying blue crabs by performing surveys on the blue crab population in the marshes around Aransas Refuge. Crab traps are set in marsh ponds to estimate the total population of blue crabs that are available as a food resource for whooping cranes. The specially designed traps catch crabs within the marsh ponds and a mark/recapture method is used to try and estimate the total population within marsh ponds.