The 56-foot Cap'n Lake

The rig will be used to broadcast seed and spat onto oyster beds in the Potomac River. It also can be converted to a harvester, hoisting oyster-growing cages from the river bottom or dredging for oysters.

Cowart Seafood had the new oyster barge built primarily to plant and harvest caged oysters and to grow oysters using a technique called spat-on-shell. The company has recently experienced some success in oyster farming using cages to grow oysters. 

Aquaculture has been successful in controlling the effects of the oyster disease MSX because cages keep oysters off the river bottom, allowing them to grow to market size faster than diseases can degrade them.

Spat-on-shell are placed in bags, lowered into tanks on shore, and left until the spat have attached to the shells. Then the spat-on-shell is broadcast over oyster shell beds on the river bottom. The goal is to get oysters to grow in clusters and stay out of the mud.

Clusters of oysters reduce losses to cownose rays. Cowart Seafood learned a hard lesson in 2005 when it planted $5,000 worth of oyster seed and found out 10 days later that cownose rays had eaten them all.

Oystermen have known for years that rays prefer to digest a single oyster. “We found that when single oysters are spread out over a bottom, a school of rays will eat them all. But when grown in clusters, they only eat about 30%,” said Lake Cowart. “That gives me 70% to harvest and sell.”