Real Science
for Real People
Hackensack River Oyster Restoration Project By Dr. Beth Ravit
The Eastern Oyster is considered a "keystone species" because they are critical in determining the structure of their ecological community. Oysters form dense aggregations, and after eggs are fertilized and the larvae hatch, the baby oysters attached to the shells of the older oysters, creating a vertical oyster reef. The oyster reef reduces water flow velocity, while providing shelter and organic material that serves as a food source for other reef inhabitants. The oyster reef creates habitat for benthic species and transitory fish, and serves as forage habitat for birds and mammals. In addition to providing a physical structure for its estuary community, an adult oyster is capable of filtering up to 10 quarts of water an hour though its body. This natural filtration process helps to reduce water turbidity, which in turn increases light transmission through the water column, creating a habitat where submerged sea grasses can grow. The oyster filtration of the river's water and the growing sea grasses improve the overall water quality.
In 1997 Hackensack Riverkeeper participated in a preliminary study to determine if young oysters could survive in the Hackensack. Juvenile oysters were housed in nets that were then placed in the river. After monitoring the oysters for a year we found that the majority of the animals survived. Riverkeeper is now initiating a project to identify locations where the growing of oyster reefs would be beneficial for the developing Hackensack ecosystem and aid in improving water quality. We will be placing new sets of juvenile oysters at different locations in the River and monitoring the animals monthly for a year to record their growth rates and ability to survive. If this test is again successful, our goal is to "plant" oyster gardens that will provide the substrate for new oysters to colonize, which will begin the process of "engineering" oyster reefs in the Hackensack River. To realize this goal Hackensack Riverkeeper is recruiting "Oyster Gardener" volunteers to work on the project. Oyster gardeners are provided with the tiny oyster "spat" - free-swimming larval oysters that attach themselves to old oyster shells. The spat on shell is housed in mesh bags, which are placed inside floats at the water surface. This system can be attached to oyster gardeners' piers, docks, or bulkheads. The only requirements are that the gardeners monitor these cages and remove any bio-fouling that collects on the structure and that the water be slightly "salty." After the oysters grow big enough to survive in the open river they are seeded in areas where the presence of an oyster reef would be beneficial for the river. |
For thousands of years the Eastern Oyster (Crassostrea
virginica) was a prominent and important member of estuary ecosystems in New
Jersey. Today, after decades of habitat degradation, disease, and over
harvesting, these animals have almost been eliminated from the Hackensack
River. Yet there may still be hope for the survival of this species in our
River - a fish study performed in 2003 by the New Jersey Meadowlands Commission
found live oysters growing in the Saw Mill Creek wildlife area of the estuary.