Virginia Sentinel Site Estimates

Sentinel sites have been established in Virginia Tributaries of the Chesapeake Bay to facilitate monitoring of oyster populations at specific locations over time. The term "sentinel site" is used to describe a monitoring station for which long-term monitoring data are available. Monitoring at sentinel sites is being performed by the Virginia Institute of Marine Science (VIMS) in collaboration with the Virginia Marine Resources Commission Shellfish Replenishment Program (VMRCSRP) in accordance with a ten year monitoring plan. The monitoring plan has been established to track progress at sentinel sites toward bay -wide oyster population restoration goals. Replenishment and restoration activities are in progress at or near many of the existing sentinel sites and, in most cases, have been deliberately paired with long term monitoring stations to help evaluate the impacts of existing restoration and replenishment efforts at a local scale.

Sentinel sites in Chesapeake Bay tributaries in Virginia waters were assigned to the following basin categories: Potomac tributaries (includes Nomini Creek , Coan River, Yeocomico River), Great/Little Wicomico, Rappahannock (includes Corrotoman River), Piankatank, York/Mobjack Bay (includes East, North, Ware, Severn, and Perrin River), James (includes Elizabeth, Lafayette, and Nansemond Rivers), and Eastern Shore (includes Tangier and Pocomoke Sounds as well as all Bay side tributaries of Virginia's Eastern Shore). These basins are shown on the map below.

VA Sentinel Map

Oyster populations at sentinel sites are evaluated using annual dredge survey data. A majority of sentinel site locations are sampled annually as a joint effort between VIMS and VMRCSRP scientists. Four dredge samples are collected each year at the jointly sampled stations. Monitoring data for these stations is reported as average numbers of oysters per bushel and average oyster biomass (g dry tissue) per bushel. A smaller number of sentinel sites are sampled by VMRCSRP scientists alone using a single dredge sample. Monitoring data for these stations is reported as number of oysters per bushel and oyster biomass (g dry tissue) per bushel. Note that ALL data provided for Virginia's sentinel sites arereported as VIRGINIA bushels (3003.9 cubic inches) as opposed to US bushels (2150.4 cubic inches) or Maryland bushels (2800.7 cubic inches).

Weather conditions, personnel constraints, and/or equipment failure may result in the absence of a sample for a site in a given year. As restoration and replenishment activites continue in the Virginia waters of the Chesapeake, sentinel sites are continually added to the existing list (35 stations in June of 2003). The absence of data for a particular site in a particular year may also be because the site was not yet established. This scenario is particularly relevant for sentinel sites that have been established to monitor oyster population development post replenishment and/or complete restoration. A table describing Virginia's sentinel sites including information on establishment date, restoration activities, and subsequent replenishment efforts is available from www.vims.edu/mollusc/cbope/VAsentinel/vasendes.htm.

Annual estimates of oyster populations at sentinel sites within Virginia's basins made with these data categories are available for:

Year	Date available	Date last modified
1994	09.02.2005	09.02.2005
1995	09.02.2005	09.02.2005
1996	09.02.2005	09.02.2005
1997	09.02.2005	09.02.2005
1998	09.02.2003	11.28.2004
1999	09.02.2003	11.28.2004
2000	09.02.2003	11.28.2004
2001	09.02.2003	11.28.2004
2002	09.02.2003	11.28.2004
2003	11.28.2004	11.28.2004
2004	03.22.2006	03.22.2006
2005	06.08.2007	06.08.2007
2006	02.13.2008	02.13.2008
2007	02.13.2009	02.13.2008
2008	02.13.2010	02.13.2010
2009	02.23.2010	02.23.2010

Annual estimates of oyster population numbers and biomass are useful for describing trends in at selected Virginia sentinel sites over time. Graphs of estimated oyster numbers and oyster biomass in the period 1994-2007 are available for: