Molluscan Ecology Program

Monitoring Programs: Oysters


Historic VIMS oyster monitoring programs

The Virginia Institute of Marine Science (VIMS) has maintained an active oyster monitoring program in Virginia waters since the 1940s. A majority of these data were collected as part of either the VIMS Spatfall Survey or the VIMS Dredge Survey. The results of these surveys have been and continue to be described in the VIMS annual oyster monitoring reports.

The VIMS Spatfall Survey deployed shell strings weekly from May through September at stations throughout the Chesapeake Bay to provide an annual index of oyster settlement and recruitment. Shell strings (12 shells on a wire; Figure 1) were suspended 0.5 m from the bottom to provide settlement substrate for oyster veligers. After retrieval, oyster spat (recently settled oysters) on the undersides of 10 shells were counted under a dissecting microscope. The average number of spat per shell was calculated for each time and place. This information (summarized in an annual report) is useful for deciding when and where to plant shell to maximize the likelihood of receiving a strike.

The VIMS Dredge Survey monitored the status of Virginia's public oyster fishery, comprising over 243,000 acres. Oyster bars throughout the state were sampled annually with a dredge to assess trends in oyster growth, mortality, and recruitment. Three samples of bottom material were dredged at each location (Figure 3). Half-bushel aliquots (25 quarts) were taken from each sample for processing. The number of spat , small, and market oysters were counted. Old and new "boxes" (dead oysters) were also counted. Averages of counts per bushel of bottom material were calculated for comparisons between areas as well as years. Note that these surveys use "Virginia" bushels as units. A Virginia bushel corresponds to 3003.9 cubic inches. A Virginia bushel differs from both a U.S. bushel (2150.4 cubic inches) and a Maryland bushel (2800.7 cubic inches). Decisions as to which areas were likely to be good sources of seed and market oysters were made annually on the basis of these data.

Modern VIMS oyster monitoring programs

Since the early 1990s, the VIMS Molluscan Ecology Program has expanded its native oyster monitoring efforts beyond the historic programs focused on Virginia's public oyster grounds to include regular monitoring efforts targeting native oyster restoration sites.

Monitoring programs examining public oyster grounds

The VIMS Molluscan Ecology group continues to conduct both the Spatfall and Dredge surveys annually. These surveys continue to provide information describing recruitment and abundance for Virginia's oyster populations and contribute to a body of knowledge describing Virginia's native oyster populations that spans more than six decades. The results of these surveys are described in the VIMS annual oyster monitoring reports.

Figure 1
Figure 2

Monitoring programs examining restoration sites

Monitoring activity is an important component of any restoration program. Monitoring data is required not only to evaluate the success or failure of a restoration effort with regard to native oyster populations but also to wisely focus effort on restoration sites with the most promise in light of years of pre-restoration data.

Since the early 1990s, the VIMS Molluscan Ecology program has partnered with Dr. Jim Wesson of the Virginia Marine Resources Commission Conservation and Replenishment Department (VMRCCRD) to regularly document the status of oyster populations at restoration sites in Virginia. Oyster populations at restoration sites are sampled non-destructively, usually through diver surveys on constructed oyster reefs.

In 2000, the VIMS Molluscan Ecology program in collaboration with Dr. Wesson at VMRCCRD began annual monitoring surveys of the oyster restoration projects established in the lower Rappahannock River as part of the Virginia Oyster Heritage Program.

More recently, the U.S. Army Corps of Engineers (ACOE) Norfolk District has become a partner with VIMS and VMRC in their ongoing efforts to restore Virginia's native oyster populations. In 2003, oyster populations at ACOE restoration sites in Tangier Sound were surveyed by VIMS and VMRC personnel. Focused monitoring efforts by VIMS in support of basin-wide ACOE native oyster restoration projects will begin in 2004 as part of the Native Oyster Restoration Monitoring (NORM) program.

VIMS oyster stock assessment programs

The VIMS oyster Patent Tong survey, was begun in 1993 in collaboration with Dr. Jim Wesson of the Virginia Marine Resources Commission Conservation and Replenishment Department to provide more quantitative estimates of oyster standing stock in Virginia's tributaries. This fishery-independent survey occupies more than 800 stations annually. At each station a patent tong samples one square meter of bottom. All of the oysters from each sample are examined. This survey provides data in support of both management and restoration of Virginia's oyster resource. Patent tong survey data are an important component of the annual estimate of Virginia's oyster population size in support of the Chesapeake Bay Oyster Population Estimation program begun in 2000 to assess Bay-wide progress toward oyster restoration goals.

The VIMS Patent Tong survey was partially supported by funds from the NOAA/Chesapeake Bay Stock Assessment Committee from 1993 through 1997. Survey results from these years were described in annual technical reports.

Related publications include:

Oyster monitoring program and stock assessment sponsors

The list of former and current sponsors of our modern oyster monitoring and stock assessment programs includes:

Document last modified 01.08.2009
© Molluscan Ecology Program. Virginia Institute of Marine Science.
All rights reserved. All images © Juliana M. Harding.