University of Maryland Center for Environmental ScienceHorn Point Oyster Hatchery

Oyster Restoration

Our oyster restoration strategy is one that was formulated as a result of the Maryland Oyster Roundtable in 1993. It was outlined in detail in the Action Plan for Oyster Restoration in Maryland. This document highlights new and innovative approaches to oyster restoration that incorporates hatcheries and the specific pathogen free oyster seed that they produce as an important tool for oyster restoration. Working under the guidelines of the Action Plan, HPL scientists and our partners have made tremendous progress in restoration techniques and have begun to experience successful restoration in some areas.

Horn Point scientists and partners have made tremendous progress in restoration techniques

Given the innovativeness of the approach, our strategies are always changing as we discover new and better methods to achieve successful restoration. However, not all restoration sites have the same goals or objectives. Some may be restored primarily for harvest, some for sanctuaries, and some for a combination of more than one goal. Different goals dictate changes in how a given oyster site is restored.

One of the most innovative approaches that has been developed during this process is the concept of managed reserves. Managed reserves combine the benefits of having large concentrations of big oysters providing habitat for other organisms, filtering water, and spawning while at the same time making available oysters for market. In order to balance the ecological benefits with the economic benefits, managed reserves are designed to minimize the effects of the oyster parasite Dermo on newly planted oyster spat by removing infected older oysters from the site prior to the deployment of spat. Watermen are involved in cleaning the bar of these adult oysters and those oysters are either brought back to the hatchery for use as broodstock or are moved to an alternate location downstream where they can subsequently be harvested.

Watermen cleaning an oyster bar

Moving diseased oysters away from the site prior to deployment of spat helps delay infection by parasites and the parasite free spat enjoy greater growth and survival. Oyster are monitored during the grow-out phase and if parasite levels become threatening they may be harvested. If parasite loads remain below acceptable limits, the oysters are allowed to grow until the mean size of oysters on a site is over 4 inches in shell height. This is an inch larger than the current size limit for oyster harvest in the Bay. Generally, it takes another year (more under poor growing conditions) for oysters to reach this larger size. This additional year is important as larger oysters filter more, spawn more, and provide more substrate and habitat than smaller oysters. Even though most of the areas where this approach is employed are in lower salinity regions where spawning occurs but recruitment is usually not very high, the other benefits are significant.

Maryland commercial watermen are working side by side with the partners to make this new approach a success. The concept of managing oysters on a bar by bar basis rather than a State-wide basis is one that may become more important to successful restoration until a solution to oyster disease is reached.