Native Oyster ('Crassostrea virginica') Restoration in Maryland and Virginia: An Evaluation of Lessons Learned 1990-2007

摘要

The Oyster Restoration Evaluation Team has assembled, collated, critically examined and analyzed the available historical oyster restoration data sets from a diverse set of sources for Chesapeake Bay. The team collected 78,000 records of activities to monitor and enhance oyster populations locally or regionally between 1990-2007. MD and VA state agencies with mandated restoration responsibilities generated most of the data. While there are data limitations that impact our ability to answer certain questions, the metadata analyses reveal a number of trends over the 18-year period of the study. Of the 1035 sites for which we found data, 81% have restoration activities, 86% have monitoring activities, and 67% have both restoration and monitoring. During the study period, five direct restoration activities were conducted bagless dredging, bar cleaning, hatchery or wild seed transplanting and substrate addition. Of these, substrate addition has been undertaken at more reefs than any other and predominantly in the tributaries. Seed transplanting has also been used extensively. While wild seed was most important during the early portion of the study period, hatchery seed transplanting began in the late 1990s and now dominates in both states. Multiple organizations (11) have participated in field visits for restoration and monitoring, often with several visits at a reef in a given year. Despite the large number of restoration activities cited above, the lack of replication across specific combinations of restoration activities within or among habitats, as well as the impact of harvest on restored reefs, severely hampers our ability to evaluate the effectiveness of restoration over the study period.