The Status of Virginia\u27s Public Oyster Resource 2008

This report summarizes data collected during 2008 in the Virginia portion of the Chesapeake Bay. The report is composed of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

The Status of Virginia\u27s Public Oyster Resource 2001

This report summarizes data collected during 2001 in the Virginia portion of the Chesapeake Bay. The report is comprised of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

The Status of Virginia\u27s Public Oyster Resource 1999

This report summarizes data collected during 1999 in the Virginia portion of the Chesapeake Bay. The report is composed of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

Observations Of Blue Crabs (Callinectes Sapidus, Rathbun 1896) On Shell Bar Oyster Reef, Great Wicomico River, Virginia

Blue crabs (Callinectes sapidus, Rathbun 1896) were sampled with commercial crab pots on Shell Bar oyster reef in the Great Wicomico River, VA, from May through October during 2006 and 2007. Weekly catch per unit effort (CPUE), sex ratio, and size (carapace width, measured in millimeters) were evaluated in the context of water temperature (measured in degrees Celsius), salinity, and daylength (measured in hours) conditions on the reef. The total number of crabs collected in 2006 and 2007 was 5,221 and 3,303, respectively. Blue crab CPU E was highest from mid-June through mid-September at water temperatures at or more than 26 C, with maximum CPUEs observed in late July. The overall annual ratio of females to males was 0.47 in 2006 and 0.60 in 2007. Males made up more than 50% of the catch at Shell Bar reef from May through August. The observed sex ratio shifted from male dominated to female dominated as salinity increased, whereas water temperature and daylength decreased seasonally. Female crabs (median carapace width (CW), 142-144 mm) were approximately 20 mm in CW larger than males (median CW, 125 mm) in both years. Annual average CPU E (13.42 crabs per pot; SE = 1.57) and maximum CPU E (32.06 crabs per pot) was twice as high in 2006 as it was in 2007. The observed interannual differences in crab CPU Es may be the result of an enhanced forage base on the reef in 2006 relative to 2007. Approximately 9 million cultchless oysters (40-80 mm in shell height) were planted on Shell Bar reef between May and October 2006 as part of a concurrent oyster rehabilitation program

Shell Length-At-Age Relationships In James River, Virginia, Oysters (Crassostrea Virginica) Collected Four Centuries Apart

Eastern oysters were ecologically and structurally dominant features of the Chesapeake Bay prior to European colonization. Four centuries of harves pressure, habitat degradation, and more recently, disease activity have affected extant oyster population demographics. We compared population demographics and age-at-shell length relationships for modern mesohaline James River oyster populations with James River oysters collected in the years 1611 to 1612 by Jamestown settlers. Historic oyster collections made by hand included a more complete demographics than modern samples collected with patent longs. Historic oysters had significantly faster growth rates than modern oyster populations. Modern oysters larger than 30-40 mm SL or age 1 grow more slowly than historic oysters of comparable ages. Unlike historic oyster populations, modern james River oyster populations are affected by Dermo and MSX. The downward trend observed in the modern age at length relationships (Fig. 4B see later) between 1 to 1.6 y is probably related to the seasonal onset of disease with increasing temperatures. Observed changes in oyster demographics and growth rates across four centuries reflect changes in the environment as well as changes in oyster biology because of chronic pressure from two oyster diseases

The Status of Virginia\u27s Public Oyster Resource 2010

This report summarizes data collected during 2010 in the Virginia portion of the Chesapeake Bay. The report is composed of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

The Status of Virginia\u27s Public Oyster Resource 2010

This report summarizes data collected during 2010 in the Virginia portion of the Chesapeake Bay. The report is composed of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

The Status of Virginia\u27s Public Oyster Resource 2010

This report summarizes data collected during 2010 in the Virginia portion of the Chesapeake Bay. The report is composed of two parts, part one, oyster recruitment (shell string) in Virginia and part two, dredge survey of selected oyster bars in Virginia

Comparison of Crassostrea virginica Gmelin (Eastern Oyster) Recruitment on Constructed Reefs and Adjacent Natural Oyster Bars over Decadal Time Scales

Since 1993, oyster reef replenishment efforts in the Virginia portion of the Chesapeake Bay have relied heavily on construction of oyster shell reefs with enhanced vertical relief. We evaluated the performance of six reefs constructed in proximity to natural subtidal oyster bars by comparing recruit densities (spat m ^ where spat are young-of-the-year oysters with shell heights less than 50 mm) between habitats. Recruitment was higher on the reefs than bars during the first 1-3 yr post-construction, usually by at least an order of magnitude. Within 7 yr, recruitment was similar between reef-bar pairs although both reefs and bars received additions of shell, live oysters, or both during the study period. At decadal time scales, constructed oyster reefs did not show enhanced recruitment relative to adjacent natural oyster bars. The rapid decline in reef recruitment post-construction is likely related to three processes: (i) shell degradation by taphonomic processes, (ii) biofouling that occludes the shell surface to recruitment, and (iii) inability of extant oysters on the reef to produce new shell at a rate commensurate with losses to (i) and (ii). There appears to be a requirement for continued replenishment activity to maintain the shell base on these reefs, contrary to the dynamics of a healthy natural oyster population. The similarity in recruitment between constructed reefs and natural bars at deeadal time scales suggests that subtidal shell plants or shell additions to natural bars may be a more cost-effective repletion strategy because they provide equal population enhancement per unit area

A Comparison Of Dredge And Patent Tongs For Estimation Of Oyster Populations

Exploited oyster stocks on public grounds in Virginia waters are subject to regular surveys effected using a traditional oyster dredge and, more recently, patent tongs. Dredges provide semiquantitative data, have been used with consistency over extended periods (decades), and provide data on population trends. Surveys with patent tongs provide absolute quantification (number of individuals per unit area) of oyster stocks but are more labor intensive. Absolute quantification of dredge data is difficult in that dredges accumulate organisms as they move over the bottom, may not sample with constancy throughout a single dredge haul, and may fill before completion of the haul thereby providing biased sampling. Selectivity of dredges versus patent tongs with respect to oyster demographics has not been rigorously examined. The objective of this study is to compare demographic oyster data collected at the same sites in the same years from both gear types. Data for the study were taken from 1993 to 2001 surveys conducted in the James River, Virginia, by the Virginia Institute of Marine Science and the Virginia Marine Resources Commission wherein the same stations were sampled by both techniques. Dredge surveys give data in oysters per bushel and assume no selective retention of live oysters with respect to shell substrate by the dredge. Patent tong surveys provide data as per tong estimates of oysters by size class and shell by volume. The hydraulically operated, 1-m square tong used in VMRC/VIMS surveys is designed to sample on and below the reef surface and include elements of buried shell that are probably not well sampled by a dredge, although the sampling ensures collection of all oysters within the tong mouth. Oysters collected by both gear types were classified as small (25-75 mm) or market (\u3e75 mm SL) for comparisons across methods. Shell volumes collected in patent tong surveys were standardized to bushel increments assuming 35.28 L of shell per bushel. The summary plots of mean values from 1993 to 2001 and 1998 to 2001 illustrate differences related to sampling gear. More shell per unit oyster (lower bushel counts) are observed in a patent tong sample. The appropriate model for attempting to fit a predictive line is open to debate, and will be influenced by patent tong penetration as determined by the degree of consolidation of the underlying substrate. The available data do not strongly support the ability to predict a relationship between dredge and patent tong population estimates at this time