the status of virginia’s public oyster resource 2000€¦ · introduction the virginia institute...

The Status of Virginia’sPublic Oyster Resource

2000

MELISSA SOUTHWORTH,JULIANA M. HARDING,

and ROGER MANN

Molluscan Ecology ProgramVirginia Institute of Marine ScienceThe College of William and MaryGloucester Point, Virginia 23062

February, 2001

The Status of Virginia’sPublic Oyster Resource

2000

MELISSA SOUTHWORTH,JULIANA M. HARDING,

and ROGER MANN

Molluscan Ecology ProgramVirginia Institute of Marine ScienceThe College of William and MaryGloucester Point, Virginia 23062

February, 2001

© 2001, Molluscan Ecology Program, Virginia Institute of Marine Science. All rights reserved.

Proper citation for this report:

Southworth, M., J.M. Harding, and R. Mann. 2001. The status of Virginia’s public oyster re-source 2000. Molluscan Ecology Program, Virginia Institute of Marine Science, GloucesterPoint, Virginia. 56 pp.

TABLE OF CONTENTS

OYSTER SPATFALL IN VIRGINIA DURING 2000 ............................................................... 4INTRODUCTION .................................................................................................................... 4METHODS ............................................................................................................................... 4RESULTS ................................................................................................................................. 6

James River ........................................................................................................................ 6Piankatank River ................................................................................................................ 6Great Wicomico River ........................................................................................................ 7Eastern Shore of Virginia.................................................................................................... 8

DISCUSSION........................................................................................................................... 8

DREDGE SURVEY OF SELECTED OYSTER BARS IN VIRGINIA DURING 2000 ..................... 30INTRODUCTION .................................................................................................................. 30METHODS ............................................................................................................................. 30RESULTS ............................................................................................................................... 31

James River ...................................................................................................................... 31York River ........................................................................................................................ 32Mobjack Bay .................................................................................................................... 32Piankatank River .............................................................................................................. 33Rappahannock River......................................................................................................... 33Great Wicomico River ...................................................................................................... 34

DISCUSSION......................................................................................................................... 34

ACKNOWLEDGEMENTS ................................................................................................... 55REFERENCES ....................................................................................................................... 55

4

particular estuary. Settlement and subsequentsurvival of spat on bottom cultch (shell) is af-fected by many factors, including physical andchemical environmental conditions, the physi-ological condition of the larvae when they set,predators, disease, and the timing of these fac-tors. Abundance and condition of bottom cultchalso affects settlement and survival of spat onthe bottom. Therefore, settlement on shellstringsmay not directly correspond with recruitment onbottom cultch at all times or places. Under mostcircumstances, however, the relationship betweensettlement on shellstrings and bottom cultch isexpected to be commensurate.

This report summarizes data collected during the2000 settlement season in the Virginia portionof the Chesapeake Bay.

METHODS

Spatfall during 2000 was monitored from the lastweek of May through mid October at all stations.Spatfall stations included eight historical sites inthe James River, three historical and five newsites in the Piankatank River, five historical andfour new sites in the Great Wicomico River andfour sites on the Eastern Shore (Atlantic Oceanside) of Virginia (Figure S1). The new sites inboth the Piankatank and Great Wicomico Riverscorrespond to those sites that were considered“new” in the 1998 survey. In this report, histori-cal sites refer to those that have been monitoredyearly for at least the past ten years whereas“new” sites are stations that were added during1998 to monitor the effects of replenishment ef-forts by the Commonwealth of Virginia. Since1993, the Virginia Marine Resources Commis-sion (VMRC) has built numerous artificial oys-ter shell reefs in several tributaries of the west-

Part I.

OYSTER SPATFALL IN VIRGINIA

DURING 2000

INTRODUCTION

The Virginia Institute of Marine Science (VIMS)monitors the reproductive activity of the East-ern oyster, Crassostrea virginica (Gmelin 1791),annually from June through October, by deploy-ing spatfall (settlement of larval oysters or spat)collectors (shellstrings) at stations throughoutVirginia in western Chesapeake Bay tributariesand on the Eastern Shore. The survey providesan estimate of a particular area’s potential forreceiving a “strike” or settlement (set) of oysterson the bottom and helps define the timing ofsettlement events. Information obtained fromthis monitoring effort is added to a database thatprovides an overview of long-term spatfall trendsin the lower Chesapeake Bay and contributes tothe assessment of the current oyster resourcecondition and the general health of the Bay sys-tem. These data are also valuable to parties in-terested in potential timing and location of shellplantings.

Results from spatfall monitoring are reflectiveof the abundance of ready-to-settle oyster larvaein an area, and thus, provide an index of bothoyster population reproduction and successfuldevelopment and survival of larvae to the settle-ment stage in an estuary. Environmental factorsaffecting these physiological activities cause sea-sonal and annual fluctuations in spatfall, whichare evident in the data.

Data from spatfall monitoring also serve as anindicator of potential oyster recruitment into a

5Molluscan Ecology Program, Virginia Institute of Marine Science

ern Chesapeake Bay as well as inshore ofFisherman’s Island and in Pungoteague Creek onthe Eastern Shore (Figure S2). The change inthe number and location of shellstring sites dur-ing 1998 was implemented to provide a meansof quantitatively monitoring oyster spatfallaround these reefs. In particular, broodstockoysters were planted on a reef in the GreatWicomico River during winter, 1996 and on reefsin the Piankatank and Great Wicomico Riversduring winter, every year since 1997, including2000. The increase in the number of shellstringsites during 1998 in the two rivers coincide withareas of new shell plantings in spring, 1998, 1999,and 2000 and provides means of monitoring thereproductive activity of planted broodstock onthe artificial oyster reefs. Continued deploymentduring 2000 of shellstrings at two Fisherman Is-land stations, was associated with concurrentecological studies on artificial (oyster shell, clamshell, and coal ash) reefs at that location. De-ployment of a shellstring at Wachapreague, Vir-ginia represents continuation of long-term datacollections at that station. Shellstrings were onceagain deployed at Pungoteague, Virginia during2000 to continue the monitoring of broodstockoyster production on the artificial oyster reef builtin the creek (Figure S2).

Oyster shellstrings were used to monitor oysterspatfall. A shellstring consists of twelve oystershells of similar size (about 76 mm, (3-in) inlength) drilled through the center and strung (in-side of shell facing substrate) on heavy gaugewire (Figure S3). Throughout the monitoringperiod, shellstrings were deployed approximately0.5 m (18-in) off the bottom at each station.Shellstrings were usually replaced after a one-week exposure and the number of spat that at-tached to the smooth underside of the middle 10shells was counted under a dissecting micro-scope. To get the mean number of spat shell-1

for the corresponding time interval, the total num-ber of spat was divided by the number of shellsexamined (ten in most cases).

Although shellstring collectors at most stationswere deployed for seven day periods, someweather related deviations did occur such thatshellstring deployment periods ranged from sixto sixteen days. These periods did not usuallycoincide among the different rivers and areasmonitored. Therefore, spat counts for differentdeployment dates and periods were standardizedto correspond to the seven day standard periodsspecified in Table 1. Standardized spat shell-1

(S) was computed using the formula:

S = Number of spat shell-1 / weeks (W)

where W = number of days deployed / 7. Stan-dardized weekly periods allow comparison ofspatfall trends over the course of the season be-tween the various stations in a river as well asbetween data for different years.

The cumulative spatfall for each station was com-puted by adding the standardized weekly valuesof spat shell-1 for the entire season. This valuerepresents the average number of spat that wouldfall on any given shell if allowed to remain atthat station for the entire sampling season. Spatshell-1 / week values were categorized for com-parison purposes as follows: 0.10-1.00, light;1.01-10.00, moderate; and 10.01 or more, heavy.Unqualified references to diseases in this textimply diseases caused by Haplosporidiumnelsoni (MSX) and Perkinsus marinus(Perkinsus, or Dermo).

Water temperature and salinity measurementswere taken at all stations. Water was collectedeach week from approximately 0.5 m off thebottom with a Niskin bottle. Temperature (de-

6 The Status of Virginia’s Public Oyster Resource 2000

grees Celcius) was then measured with an alco-hol thermometer and salinity (in ppt, or parts perthousand) was measured with a hand-held refrac-tometer.

RESULTS

Spatfall on shellstring collectors for 2000 is sum-marized in Table S1 and is discussed below foreach river system monitored. A summary ofsettlement at the historical stations for the past11 years appears in Table S2. Unless otherwisespecified, the information presented below re-fers to those two tables. When comparing 2000data with historical data in the James River, alleight stations were used. Due to the addition ofnew sites during 1998 in the Piankatank andGreat Wicomico Rivers, any comparison madeto historical data could not include data from allof the sites sampled during 2000. Historical sitesin the Piankatank are Burton Point, Ginney Point,and Palace Bar. Historical sites in the GreatWicomico include Fleet Point, Glebe Point,Haynie Point, Hudnall, and Whaley’s East(Cranes Creek in previous data reports).

James River

Oyster settlement in the James River was firstobserved during the week of July 8 at WreckShoal (Table S1). Settlement began at all otherstations during the week of July 15 and contin-ued sporadically at all stations until the end ofSeptember. There were two major pulses of oys-ter set in the James River. The first occurred inmid July, the second occurred in mid September(Figure S4).

Cumulative spat shell-1 / week for 2000 rangedfrom a low of 0.7 at Deepwater Shoal and Pointof Shoal to a high of 4.3 at Day’s Point. Settle-ment was light to moderate at all stations, with

heavier settlement tending to occur at the sta-tions located nearer to the southern shore of theriver.

The slight improvement in spatfall in the JamesRiver, which occurred during 1999, did not con-tinue into 2000. Settlement during 2000 waslower at all stations compared to settlement dur-ing 1999 (Table S2: Figures S5A and S5B).However, settlement during 2000 was slightlyhigher when compared with the five year meanat Horsehead and Day’s Point. Settlement at allstations was lower when compared with the tenyear mean (Table S2: Figures S5A and S5B).

Average river water temperatures reached a maxi-mum in early August (29.1 degrees Celcius: Fig-ure S6A). Water temperatures throughout the2000 sampling season were normal when com-pared with the mean for the previous five years(Figure S6A). For the most part, salinity in theJames River during the 2000 sampling period wasalso similar to the previous five year mean. How-ever there were a few weeks (June 10 throughJuly 15) early in the season when a lack of raincaused the salinity to rise 3 to 4 ppt higher thannormal. During this time there were large fluc-tuations in ambient salinities such that salinitychanged as much as 8 ppt from one week to thenext. On average there was a 6 to 9 ppt salinitydifference between Deep Water Shoal (the mostupriver station) and Day’s Point (the mostdownriver station: Figure S1), a slightly higherdifference than in previous years.

Piankatank River

Settlement in the Piankatank River was first ob-served during the week of July 22 at Stove Pointand July 29 at Burton Point (Table S1). Settle-ment began at all other stations except WiltonCreek, during the week of August 12. Settle-


ment was very sporadic throughout the river withonly one major pulse occurring in mid August(Figure S7). Cumulative spat shell-1 / week forthe year ranged from a low of 1.2 at Cape Toonto a high of 6.8 at Ginney Point. Prior to the2000 reproductive season (spring, 2000) threeevents that might affect oyster spatfall occurredin the Piankatank River. Broodstock oysters wereplaced on oyster reefs near Bland Point, IronPoint, Burton Point, and Palace Bar (Figure S2).Seed/oysters were removed from Cape Toon,Bland Point, Palace Bar, Heron Rock, and Bur-ton Point and clean shells (cultch) were thenplanted on those five bars (Figure S1), to pro-vide clean substrate for larval oysters to set on.Comparing the major spatfall in the two areaswith broodstock oysters, the larvae appeared totravel and set upriver and adjacent to thebroodstock oysters.

Spatfall during 2000 showed a decrease from1999 at two out of the three historical stations(Table S2: Figure S8). Ginney Point was the onlysite (historical and new) that showed an increasewhen compared with 1999. Spatfall during 2000showed an increase at Ginney Point and PalaceBar when compared with the five year mean butwas still low for all three historical sites whencompared with the ten year mean.

The average Piankatank River water temperatureranged from 19 to 28 degrees Celcius through-out the sampling period, reaching a maximumin mid June and again in mid July. Water tem-perature did not vary much from the average tem-peratures previously recorded in the river (Fig-ure S9A). Salinity ranged from 11 to 16 pptthroughout the sampling period. There was littledifference in salinity in the river when comparedwith the mean for the previous five years (Fig-ure S9B). During 2000, there was anywhere froma 1 to 4 ppt difference recorded between Wilton

Creek (the most upriver station) and Burton Point(the most downriver station: Figure S1).

Great Wicomico River

Settlement in the Great Wicomico River was firstobserved during the week of July 1 (Table S1) atHudnall and the week of July 22 at Haynie Point.No other settlement was observed until the be-ginning of August. As in the Piankatank River,settlement in the Great Wicomico was very spo-radic, with one major pulse occurring in lateAugust/early September (Figure S10). GlebePoint experienced the biggest pulse in settingduring 2000. The pulse at Glebe Point occurredapproximately two weeks before it occurredthroughout the rest of the system. Prior to the2000 reproductive season (spring, 2000), oystershell was planted at Rogue Point, Hilly Wash,Shell Bar, and Harcum Flats (Figure S1).Broodstock oysters were placed on the artificialoyster reef located at Shell Bar (Figure S2).

Cumulative spat shell-1 / week for the year rangedfrom a low of 0.2 at Whaley’s East to a high of4.2 at Glebe Point. As observed in 1999, settle-ment at all stations in 2000 (both historical andnew, except Whaley’s East) was higher than dur-ing the previous season’s settlement. However,comparing 2000 numbers with those recordedover the past few years, overall settlement in theGreat Wicomico was low for the third consecu-tive year. Settlement at the historical stationsduring 2000 was also much lower than both thefive and ten year means (Table S2: Figure S11).

Average river water temperatures ranged between21 and 30 degrees Celcius throughout the sam-pling period (Figure S12A). Water temperaturereached a maximum in mid July. Unfortunately,due to lack of historical data for the GreatWicomico neither temperature nor salinity dur-


ing 2000 could be compared with the previousfive year mean as it was in the James andPiankatank Rivers. However, comparing thesalinity values recorded during 2000 with thosefrom 1998 and 1999 (Figure S12B) the patterntends to be on the average (normal) side (as inthe James and Piankatank Rivers), as do the tem-perature values. There was a 1 to 2 ppt differ-ence in salinity between the most upriver station(Glebe Point) and the most downriver station(Fleet Point: Figure S1) throughout a majorityof the sampling season.

Eastern Shore of Virginia

As has been observed over the past two years,settlement at the Pungoteague reef site was low,with a total of 0.2 cumulative spat shell-1 / week.One spat set during the week of July 22 and oneset during the week of September 30 (Table S1).Water temperature at the Pungoteague sitereached a maximum of 28 degrees Celcius in thebeginning of August and fluctuated between 22and 28 degrees Celcius for the majority of thesampling season (Figure S15A). Salinity at thesite ranged between 16 and 23 ppt (Figure S15B).

Settlement was first recorded at both FishermanIsland sites during the week of July 22. Spatfallwas consistent (at least one spat shell-1 everyweek) from the end of July through mid Sep-tember (Figure S13). As has been observed overthe previous five years, more spat settled at thenorthern site when compared to the southern site(Table S1: Figure S14). Settlement at both siteswas considerably lower than that recorded overthe past three years. The cumulative spat shell-1

/ week was 7.2 for Fisherman Island south and9.9 for Fisherman Island north. Water tempera-ture and salinity were similar for both Fisher-man Island sites throughout most of the season.The break in temperature and salinity data in

early July (Figures S15A and S15B) for Fisher-man Island south, is due to the shellstring at thatsite being lost for three weeks in a row. Tem-perature ranged between 19 and 27 degreesCelcius and salinity ranged between 26 and 34ppt throughout most of the sampling season.

Settlement was first observed at theWachapreague site during the week of July 22.Spatfall was intermittent from the end of Julythrough the end of the sampling season (TableS1). Prior to 1999, settlement at Wachapreaguehad been steadily increasing each year since hit-ting an all time low in 1994. Settlement atWachapreague was once again low during 2000,lower than any recorded in the previous ten years(Table S2: Figure S14). Water temperature andsalinity at the Wachapreague site was similar tothe values recorded at the Fisherman Island sites(Figures S15A and S15B).

DISCUSSION

Oyster spatfall during 2000 was low to moder-ate in all Virginia tributaries of the western shoreof the Chesapeake Bay. Low spatfall has beenprevalent in Virginia since 1991, with the excep-tion of parts of the James River in 1993, and tosome extent the Great Wicomico River in 1997and the Piankatank River in 1999. Spatfall at allsites during 2000 was lower than the previousten year mean (1990-1999). It was also lowerthan the previous five year. mean (1995-1999),with the exception of Horsehead and Day’s Pointin the James River and Ginney Point and PalaceBar in the Piankatank River.

Overall oyster settlement during 2000 in theJames River was similar to that observed overthe past five years. Spatfall during 2000 for bothHorsehead and Day’s Point was slightly higherthan the previous five year mean. Nonetheless,


it was still low throughout the system when com-pared with observed settlement over the past tenyears. Historically, spatfall in the James tendsto be highest at the more downriver stations (i.e.,those with a higher salinity) and along the south-ern shore of the river: Day’s Point, Rock Wharf,and Dry Shoal. Settlement at those three sitesconstituted between 55 and 75% of the total an-nual spatfall at all stations monitored in eight outof the past thirteen years. When the other threedownriver stations that used to be monitored priorto 1998 are included in the analysis, these sixsites accounted for 60 to 90% of the total settle-ment in the river for the years 1988 to 1997. Inthree of the past thirteen years, the other five sitesconstituted between 61 and 65% of the total forthe year and the other two years were approxi-mately a 50/50 split. While this historical pat-tern of settlement was not completely mirroredin 2000, with the exception of low spatfall atRock Wharf and Point of Shoals, settlement didincrease in a seaward direction along the south-ern shore. Rock Wharf has had moderate settle-ment over the past few years, but for some rea-son did not see as much success in 2000.

The first peak in settlement in the James Riveroccurred earlier in the year than is normal, midJuly vs. mid to late August. This may have beendue to the large salinity fluctuations observed inthe system early on in the season. From the weekof June 10 through July 15, the salinity changedas much as 8 ppt between weeks. While watertemperature is thought to play a larger role intiming of the spawn, salinity, specifically rapidchanges in salinity, can also effect both spawn-ing and survival in the plankton (Thompson etal., 1996).

While not quite as high as observed during 1999,settlement in the Piankatank River during 2000was among the highest seen since 1992. The

increase in spatfall throughout the Piankatanksystem starting in 1998, can probably be attrib-uted to the placement of broodstock oysters onthe artificial oyster reefs located in the river (Fig-ure S2). The highest settlement of oysters oc-curred around and upriver of these reefs. Thelocation of settlement of spat during the past fewyears supports the suggestion that the PiankatankRiver is a trap-type estuary (Andrews, 1983).

Oyster settlement in the Great Wicomico Riverwas light to moderate. However, all stationsexcept Whaley’s East showed an improvementcompared with 1999 spatfall. One major factorin the difference between 1999 and 2000 couldbe the location of broodstock placement.Broodstock were planted on Cranes Creek Reefin 1999 and on Shell Bar Reef in 2000 (FigureS2). Shell Bar Reef is located upriver of the sandspit at Sandy Point whereas Cranes Creek is lo-cated closer to the mouth of the river, downriverof the sand spit. The sand spit at Sandy Point isan important feature in the river in that it con-tributes to the upriver retention of larvae in thesystem and the trap-type nature of the estuary(Southworth and Mann, 1998).

The shellstrings on the reef at Pungoteague con-tinue to receive low spatfall (two spat through-out the entire season) as has been prevalent sincethe reef was constructed in 1997. Similar to whatwas seen during 1999, Pungoteague Reef hadhigher settlement than that seen on theshellstrings, although settlement on the reef dur-ing 2000 was not as high as 1999 (J. Wesson,VMRC, Shellfish Replenishment Program, New-port News, Virginia; personal communication).The difference in settlement on the reef is mostlikely due to the absence of “new” broodstockon the reef during 2000 (none were planted),whereas there were broodstock planted during1999. However, there is still disagreement in


settlement numbers on the reef and settlementnumbers on the shellstrings, regardless ofwhether or not broodstock are planted on the reef.One possible explanation for the lack of settle-ment on the shellstrings could be the circulationpatterns in the area. Often times there are largediscrepancies between settlement on the bottom(or just off the bottom in the case of shellstrings)and settlement on the reefs. This difference maybe due to small changes in circulation patternsaround the shellstring site, flushing the larvaeaway from the area. The potential for small-scalecirculation to affect settlement is supported bydiscrepancies in settlement location observed onthe reef itself. Settlement on the reef during both1999 and 2000 was highest in the subtidal andmid reef area and very low at depth on the reef,near the bottom where the shellstrings are lo-cated.

Compared to the past few years, the remainingEastern Shore sites had relatively low settlementduring 2000. Settlement at Wachapreague wasseveral orders of magnitude lower during 2000than both the five and ten year means for thatsite. At the Fisherman Island sites, the spatfallnumbers were the lowest recorded since the reefswere built in 1995 and 1996 (Morales-Alamo andMann, 1998).

Settlement in the James and Piankatank Riversand on the Eastern Shore was lower during 2000than during 1999. One possible explanation forlow settlement in the Piankatank River is thebloom of the dinoflagellate Prorocentrum mini-mum that occurred in late spring, early summer(Old Dominion University, unpublished data).This dinoflagellate has been shown to have det-rimental effect on oyster reproduction as well aslarval development and survival (Luckenbach,et al., 1993). The Great Wicomico River wasthe only system that appeared to show an im-

provement in settlement from the previous year.The Great Wicomico had relatively low settle-ment during 1999, most likely due to high dis-ease prevalence and a large die-off of small andmarket size oysters early in the spawning season(Calvo and Burreson, 2000). Added to that fac-tor was the lack of broodstock on Shell Bar Reef(Figure S2), which has been shown to be an im-portant area in terms of circulation and larvalretention in the system (Southworth and Mann,1998). Given these two factors, what appears tobe an increase in spatfall during 2000, may justbe a recovery from the mortality observed in theprevious year combined with the added effect ofbroodstock on Shell Bar Reef.


Figure S1: Map showing the location of the 2000 shellstring sites including those sites in the 3western tributaries and on the Eastern Shore. Numbers in the blown up maps of the Piankatank andGreat Wicomico Rivers are represented by the closed black circles on the big map. An “N” follow-ing the site name indicates a new site as specified in the text; all other sites are historical.

James River: 1) Deep Water Shoal, 2) Horsehead, 3) Point of Shoal, 4) Swash, 5) Dry Shoal, 6)Rock Wharf, 7) Wreck Shoal, 8) Day's Point.

Piankatank River: 9) Wilton Creek (N), 10) Ginney Point, 11) Palace Bar, 12) Bland Point (N),13) Heron Rock (N), 14) Cape Toon (N), 15) Stove Point (N), 16) Burton Point.

Great Wicomico River: 17) Glebe Point, 18) Rogue Point, 19) Hilly Wash (N), 20) HarcumFlats (N), 21) Hudnall, 22) Shell Bar (N), 23) Haynie Point, 24) Whaley's East, 25) Fleet Point.

Eastern Shore: 26) Pungoteague, 27) Wachapreague, 28) Fishermans Island.


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Figure S2: Map showing the location of the artificial oyster reefs in the Virginia portion of theChesapeake Bay.

Lynnhaven River: 1) Lynnhaven River Reef.

Lafayette River: 2) Hampton Boulevard Bridge Reef, 3) Tanner's Point Reef.

Elizabeth River: 4) Western Branch Reef, 5) Craney Island Reef.

York River: 6) Felgate's Creek Reef, 7) Amoco Reef.

Mobjack Bay: 8) Ware River Reef, 9) North River Reef, 10) East River Reef.

Piankatank River: 11) Palace Bar Reef, 12) Bland Point Reef, 13) Iron Point Reef, 14) Bur-ton Point Reef.

Rappahannock River: 15) Ferry Bar Reef, 16) Drumming Ground Reef, 17) Temple BayReef, 18) Parrot's Rock Reef, 19) Mill Creek Reef, 20) Sturgeon Bar Reef, 21) Broad CreekReef, 22) Butler's Hole Reef.

Great Wicomico River: 23) Shell Bar Reef, 24) Cranes Creek Reef.

Potomac River: 25) Yeocomico River Reef, 26) Coan River Reef.

Eastern Shore: 27) Pungoteague Creek Reef, 28) Fishermen’s Island Reefs.


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30

Part II.

DREDGE SURVEY OF SELECTED

OYSTER BARS IN VIRGINIA

DURING 2000

INTRODUCTION

The Eastern oyster, Crassostrea virginica(Gmelin 1791), has been harvested from Virginiawaters as long as humans have inhabited the area.Depletion of natural stocks during the late 1880sled to the establishment of oyster harvestingregulations by public fisheries agencies. A surveyof bottom areas in which oysters grew naturallywas completed in 1896 under the direction ofLt. J. B. Baylor, U.S. Coast and Geodetic Survey.These areas (over 243,000 acres) were set asideby legislative action for public use and have cometo be known as the Baylor Survey Grounds orPublic Oyster Grounds of Virginia; they arepresently under management by the VirginiaMarine Resources Commission (VMRC).

Every year the Virginia Institute of MarineScience (VIMS) conducts a dredge survey ofselected public oyster bars in Virginia tributariesof the western Chesapeake Bay to assess thestatus of the existing oyster resource. Thesesurveys provide information about spatfall andrecruitment, mortality, and changes in abundanceof seed and market-size oysters from one year tothe next. This section summarizes data collectedduring bar surveys conducted during October2000.

Spatial variability in distribution of oysters overthe bottom can result in wide differences amongdredge samples. Large differences amongsamples collected on the same day from one barare an indication that distribution of oysters overthe bottom is highly variable. An extremeexample of that variability can be found inSouthworth et al. (1999) by the width of theconfidence interval around the average count ofspat at Horsehead (James River, Virginia) during1998. Therefore, in the context of the present

sampling protocol, differences in average countsfound at one bar between seasons in the sameyear or between counts for the same season indifferent years may be the result of samplingvariation rather than actual short-term changesin abundance. If the observed changes persistfor several years or can be attributed to well-documented physiological or environmentalfactors, then they may be considered a reflectionof actual changes in abundance with time.

METHODS

Location of the oyster bars sampled by VIMSduring October 2000 are shown in Figure D1.Geographic coordinates of the bars are given inTable D1.

Four samples of bottom material were collectedat a single station on each bar using an oysterscrape dredge. In all surveys preceding 1995,sampling was effected using a 2-ft wide dredgewith 4-in teeth towed from a 21-ft boat; volumecollected in the dredge bag was 1.5 bushels.Beginning in 1995, samples were collected usinga 4-ft dredge with 4-in teeth towed from the 43-ft long VMRC vessel J. B. Baylor; volumecollected in the bag of that dredge is threebushels. In all surveys a half-bushel (25 quarts)subsample was taken from each tow forexamination. Data presented give the averageof the four samples collected at each station forlive oyster and box counts after conversion to afull bushel.

From each half bushel sample, the number ofmarket oysters (76 mm (3-in), in length or larger),small oysters (< 76 mm (3-in), excluding spat),spat (recently settled (2000 recruits)), new boxes(inside of shells perfectly clean; presumed deadfor approximately < 1 week), old boxes, and spatboxes were counted. The presumed time periodsince death of an oyster associated with the twocategories of boxes is a qualitative descriptionbased on visual observations.

During spring and early summer 2000, thefollowing changes that may have had some effecton settlement and oyster abundance were made


(Figure D1 and D2 for locations). Seed wasremoved from Palace Bar, Burton Point, BlandPoint, Cape Toon, and Heron Rock in thePiankatank River and moved to several differentbars throughout the Chesapeake Bay includingMorattico Bar in the Rappahannock River. Cleanshells (cultch) were then planted on the five bars(listed above) in the Piankatank River and onShell Bar, Harcum Flats, Rogue Point, and HillyWash in the Great Wicomico River to providesubstrate for oyster larvae to settle on. Six newartificial oyster reefs were built in theRappahannock River at Sturgeon Bar, MillCreek, Parrot Rock, Temple Bay, DrummingGround, and Ferry Bar. The reefs at Broad Creekand Butler’s Hole (Figure D2) are slated to bebuilt in spring, 2001. Cultch was planted aroundthe Parrot Rock and Drumming Ground Reefs.Prior to this, Drumming Ground was completelycleaned of oysters (all sizes) and for that reasonis treated as a “new” site in the 2000 data. Theoysters from Drumming Ground were thentransplanted to Parrot Rock and Middle Ground.In addition, broodstock oysters were planted onthe artificial reefs at Iron Point, Palace Bar,Burton Point, and Bland Point in the PiankatankRiver and on Shell Bar Reef in the GreatWicomico River. In mid 1999 an artificial oysterreef was built in the York River in Felgates Creekand 2 reefs were built in Mobjack Bay: one inthe North River (Cradle Point) and one in theEast River (Mobjack Point). A third reef wasbuilt in the Ware River during 2000. Temperature(in degrees Celcius) and salinity (in ppt, partsper thousand) were recorded at each of the dredgestations at the time of sampling using an alcoholthermometer and a hand-held refractometer.

RESULTS

Thirty oyster bars were sampled between October10 and 26, 2000, in six of the major Virginiatributaries on the western shore of theChesapeake Bay. Bar locations are shown inFigure D1 and Table D1. It should be noted thatBell Rock in the York River is a private bar andis included in this report for historical reasons.Results of this survey are summarized in TableD2 and unless otherwise indicated, the numberspresented below refer to that table.

James River

Ten bars were sampled in the James River,between Nansemond Ridge at the lower end ofthe river and Deep Water Shoal near theuppermost limit of oyster distribution in thesystem. The highest average number of oystersbushel-1 of all sizes was found at Horsehead(681), as has been the case for the past severalyears excluding 1998. The number of oysters atSwash, Point of Shoal, and Long Shoal wasmoderate ranging from 413 to 487 oysters bushel-1. Total number of oysters at all other bars wasrelatively low averaging less than 250 bushel-1,with a range of 33 (Dry Shoal) to 218 (MulberryPoint) total oysters bushel-1.

As has been the case during the past few years,the number of market oysters in the James Rivercontinues to be low, with the majority of thembeing found at the most upriver sites (Figure D1).The number of market oysters at the five mostupriver sites (Figure D1) ranged between 11(Swash) and 36 bushel-1 (Deep Water Shoal)whereas the five down river stations hadconsiderably fewer market oysters rangingbetween zero (Dry Shoal) and 7 (Wreck Shoal)bushel-1. Comparing the data for the numbersof market oysters over the past four years (1997-2000) there appears to be little change at most ofthe sites monitored (Figure D3, D4A, and D4B).There was a noticeable increase in market oystersat Horsehead from 1997 to 1998 and this trenddoes appear to be real. There has been a steadydecrease in the number of market oysters foundat Long Shoal during the past four years (FigureD3). The number of market oysters at Dry Shoalwas low but stable for three years in a row until2000, when it dropped to zero market oystersbushel-1.

The number of small oysters bushel-1 rangedfrom a low of 14 (Thomas Rock) to a highof 615 (Horsehead). The composition of theoyster populations at all of the sites exceptThomas Rock and Nansemond Ridge was madeup of greater than 50% small oysters. Horseheadand Long Shoal had the greatest percentage ofsmall oysters at a little over 90% of the total.While the number of small oysters found at


Nansemond Ridge continues to be low, there hasbeen a noticeable increase at the site during thepast few years (Figures D3 and D4A). Similarto the change in the number of market oysters atDry Shoal, there was also a noticeable decreasein small oysters at that site between 1999 and2000 (Figure D3 and D4B). There has been verylittle change in numbers of small oysters at anyof the other sites during the past few years.

The number of spat bushel-1 ranged from a lowof 11 (Dry Shoal) to a high of 88 (NansemondRidge). The number of spat found throughoutthe system in 2000 was relatively low. Therewas a noticeable decrease between 1999 and2000 in the number of spat bushel -1 seen at allof the sites except Deep Water Shoal andHorsehead (Figure D3: Figure D4A and B). Ashas been observed in the James River in the past,there is a relationship between location in theriver and the composition of live oysters in termsof percentage of oysters found in each size class.As one moves from the most upriver station(Deep Water Shoal) to the most downriver station(Nansemond Ridge: Figure D1), the percentageof small oysters tends to decrease while thepercentage of spat tends to increase.

The average number of boxes bushel-1 rangedfrom a low of eight (Thomas Rock) to a high of96 (Dry Shoal). At Dry Shoal and Wreck Shoal,boxes accounted for over 23% of the total oystersfound (live and dead). At the remaining eightstations between 10 and 18% of the total numberof oysters were boxes. On Dry Shoal, 32% ofthe total number of oysters (live and dead) wereboxes. The high percentage of boxes mayaccount for the overall low number of oystersrecorded at that site during 2000.

Water temperature during the sampling periodremained fairly constant ranging from 17.4 to18.6 degrees Celcius (Table D2). Salinity wasmore variable depending on location in the river,increasing in a downriver direction, from 11 pptat Deep Water Shoal to 17 ppt at Thomas Rockand Nansemond Ridge.

York River

The average total number of live oystersbushel-1 in the York River were similar for bothbars sampled (61 at Aberdeen Rock, 88 at BellRock). The oysters found at Aberdeen werepredominately small oysters (86% of total), whilethe oysters at Bell Rock were about a 50/50 splitof small and spat, with a slightly higherpercentage of spat. There has been a steadyincrease in the number of small oysters atAberdeen Rock during the past few years (FigureD5 & D6). There was also a noticeable decreasein the number of spat between 1999 and 2000 atthat site. Market oysters were scarce at bothbars, accounting for 1 and 18% of the total liveoysters at Aberdeen Rock and Bell Rockrespectively. The total number of boxes (newand old) bushel-1 was low at both bars sampledin the river. Water temperature at both stationswas 18.9 degrees Celcius on the day of sampling.There was a 5 ppt difference in salinity, 14 ppt atBell Rock and 19 ppt at Aberdeen Rock.

Mobjack Bay

The average total number of live oystersbushel-1 in Mobjack Bay was 32 at Pultz Bar and185 at Tow Stake. Pultz Bar oysters consistedof approximately 50% spat, with the other 50%being an equal mix of small and market sizeoysters. There was a noticeable decrease in thenumber of small and market oysters and a slightincrease in the number of spat at Pultz Barcompared with 1999 (Figure D5 and D6).Overall the total number of oysters found at PultzBar continues to be low. The composition of liveoysters at Tow Stake consisted of a 50/50 mixtureof small oysters and spat, with very few marketsize oysters. There was little difference in anysize category at Tow Stake between 1999 and2000. However, the number of market oysterhas been consistently increasing for the past fewyears and the increase in spat observed during1998 appears to be sustained. The total numberof boxes was relatively high, making up 18 and32% of the total number of oysters found (liveand dead) at Tow Stake and Pultz Barrespectively. In contrast to the 1999 dredgesurvey (Southworth et al., 2000), there were


fewer boxes attributed to oyster drills in the fall2000 sampling. Water temperature at bothstations was 21.1 degrees Celcius on the day ofsampling. There was a 1 ppt difference in salinity,17ppt at Pultz Bar and 18 ppt at Tow Stake.

Piankatank River

The average total number of live oysters bushel-1 in the Piankatank River was moderate at PalaceBar (457) and low to moderate at Burton Point(181) and Ginney Point (371). The number ofmarket size oysters at all three stations wasrelatively low. There was approximately a 50/50 mixture of spat and small oysters on all 3 bars,with a slightly higher percentage of small beingfound atGinney Point and Burton Point and slightlyhigher percentage of spat being found at PalaceBar. As such, there was a noticeable increase insmall oysters and a noticeable decrease in thenumber of spat at all three sites (Figure D7 andD8) between 1999 and 2000. There was also aslight decrease between 1999 and 2000 of marketoysters at all of the sites. There were a relativelyhigh number of boxes at Ginney Point (147)accounting for 28% of the total oysters (live anddead) sampled. The number of boxes at PalaceBar and Burton Point were moderate, accountingfor 11 and 18% of the total respectively. On theday of sampling, water temperature at all threesites was 17.5 degrees Celcius and salinity rangedfrom 13 to 15 ppt (Table D2).

Rappahannock River

The average total number of live oysters in theRappahannock River was low at all ninestations sampled (disregarding DrummingGround since it was cleaned of oysters in spring2000 and is now considered a “new” site) rangingfrom 3 (Hog House) to 239 (Middle Ground)bushel-1. As mentioned in the Methods section,Middle Ground was seeded with oysters in spring2000, which probably accounts for the relativelyhigh (when compared with the other sites in theriver) number of oysters found there. Thereappears to be no relation between the totalnumber of live oysters and location in the river

(i.e. upriver vs. downriver: Figure D1),temperature, or salinity (Table D2). Small oystersmade up the highest percentage of oysters at allof the sites ranging from 60 to 94% of the total.

As has been found for the past few years, BroadCreek had the most market oysters with 27bushel-1. Broad Creek also had the most smalloysters (115 bushel-1) of any of the bars notseeded with oysters in spring 2000 (seeMethods). There were little or no spat found atmost of the sites sampled. The two sites withthe most spat are located near the mouth of andin the Corrotoman River (Drumming Ground andMiddle Ground: Figure D1) which had 14 and16 spat bushel-1 respectively.

There was a noticeable decrease in spat seen atall nine sites (Drumming Ground was notincluded in the analysis) when compared with1999 (Figures D9, D10A, and D10B). LongRock, Smokey Point, and Broad Creek showeda noticeable increase in the number of smalloysters compared to 1999, while Ross Rock andHog House showed a decrease (Figure D9). Thedecrease in market oysters at Broad Creek seenin 1999, the first in six years at this site, heldsteady between 1999 and 2000 (Figure D10A).There has been a steady decrease in marketoysters at Bowlers Rock over the past few yearsand a decrease between 1999 and 2000 at HogHouse, Long Rock,and Ross Rock.

The number of boxes bushel-1 (new and old)ranged from 1 (Ross Rock and Hog House) to55 (Smokey Point). A moderate percentage ofoysters (live and dead) at all of the stationssampled except Ross Rock were boxes (16 to33%). There were no spat boxes found at any ofthe sites.

Water temperature on the day of sampling rangedfrom 17.2 to 18.3 degrees Celcius. Salinityincreased moving from the most upriver station(Ross Rock: 8 ppt) toward the mouth (BroadCreek: 20 ppt).


Great Wicomico River

The average total number of live oysters at allthree stations sampled in the Great WicomicoRiver was low ranging from 68 bushel-1

(Whaley’s East) to 92 bushel-1 (Fleet Point). Thelive oysters found were predominately small,accounting for 75% (Haynie Point), 81% (FleetPoint), and 84% (Whaley’s East) of the total.This predominance was coupled with anoticeable increase in small oysters and anoticeable decrease in spat at all three stationswhen compared with 1999 (Figures D11 andD12). There was no difference in the number ofmarket oysters at any of the sites between 1999and 2000. There appears to be no pattern in anysize class at any of the sites observed over thepast few years (Figure D11). Boxes made up 29(Haynie Point) to 39% (Whaley’s East) of thetotal (live and dead) oysters counted. The totalnumber of boxes was about half the number oflive oysters at all three sites. As observed inpast years, greater than 88% of the boxes wereold. Water temperature was between 17.5 and18.3 degrees Celcius and salinity was between19 and 20 ppt on the day of sampling.

DISCUSSION

As is well known, the abundance of marketoysters throughout the Chesapeake Bay regionhas been in serious decline since the turn of thecentury. In recent years the greatestconcentration of market oysters on Virginiapublic grounds has been found at the upper limitsof oyster distribution (lower salinity areas) in theJames River and Rappahannock River, with theexclusion of Broad Creek in the RappahannockRiver. Presently, the abundance of market oystersin the Virginia tributaries of the Chesapeakeremains low. Of the Virginia bars sampled duringthe 2000 survey, the highest number observedwas 36 market oysters bushel-1 (Deep WaterShoal). At the bars where the total number oflive oysters was greater than 100 bushel-1, marketoysters constituted between 1 and 18% of thattotal.

As in recent years, the bulk of the oysterpopulation during 2000 consisted primarily of

small oysters. Thomas Rock and NansemondRidge in the lower James River, Bell Rock inthe York River, Pultz Bar in Mobjack Bay, andPalace Bar in the Piankatank River, were the onlybars with a higher percentage of spat than smalloysters. The oyster populations at the other 25sites all had a greater percentage of small oysters,with the exception of Ginney Point in thePiankatank, which had a 50/50 mixture of smalland spat. Similar to historical patterns of oysterabundance in the James River, as one movestoward the mouth, the number of spat increaseswhile the number of small oysters decreases.Circulation in the system is such that oysterlarvae from the upper limits of oyster abundance(lower salinity areas) are flushed further downriver to set at the higher salinity sites (Haven andFritz, 1985). One would expect that over timethis would translate into an increase in small andmarket oysters at the higher salinity sites. Themost likely explanation for why this does notappear to be the case is disease. Both Perkinsusmarinus and Haplosporidium nelsoni increase inintensity and prevalence as salinity increases(Calvo and Burreson, 2000).

The 1998 dredge survey in the James Rivershowed an increase in spat from the previousyear. In general this increase was not observedagain during 1999 or 2000 (there was an evenfurther decrease between 1999 and 2000), norwas it reflected in the number of small oystersobserved. As discussed in the 1998 dredge report(Southworth et al., 1999), one must look at thetiming of set when interpreting the data. In yearswhen spatfall occurs earlier (as in 1999 and2000), the natural mortality that occurs post-settlement occurs over a longer time frame (interms of time from set to sampling). Forexample, say overall 1000 spat bushel-1 setduring both years. However during 1999 theydidn’t all set until the end of September, whereasduring 2000, they were all set by the end ofAugust, creating a difference of one-month post-settlement mortality time. Assuming a mortalityrate of 50% each month, by sampling time during2000 there would be 500 spat bushel-1, whereasduring 1999 there would only be 250 spatbushel-1. During 1998, the majority of thespatfall occurred later in the season (September),


allowing for less time for post-settlementmortality to occur. Given the lack of an increasein small oysters and spat in both the 1999 and2000 samples, the apparent increase in spatfallrecorded in the 1998 samples was most likelynot a true increase in spat, but rather adiscrepancy due to a change in temporal scale.

Overall, oyster settlement on all of the barssampled during 2000 was low, much lower thanthat recorded during 1999. One possibleexplanation for the lack of spatfall, in comparisonto 1999 could be temporal changes in timing ofthe set, as previously mentioned. Settlement onthe shellstrings during 2000 occurred earlier inthe year than usual in the James, Piankatank, andGreat Wicomico Rivers. Another component thatmay have caused low settlement during 2000could have been the bloom of the dinoflagellateProrocentrum minimum. This dinoflagellatebloom occurred in late spring/early summer, inthe upper reaches of several of the tributaries ofthe Chesapeake Bay including the Piankatankand Great Wicomico Rivers (Old DominionUniversity, unpublished data). Thisdinoflagellate has been shown to limit spawningin adult oysters and can impair larvaldevelopment causing high mortalities in larvalcultures (Luckenbach et al., 1993). Other factorscould also have been involved such that 1999was simply an unusually good year for spatfall.Salinity during 1999 was 4 to 6 ppt higher thannormal throughout most of the spawning season(Southworth et al., 2000) and while temperatureis thought to have a greater role in spawningsuccess and timing, salinity can also have aneffect (Thompson et al., 1996). The combinationof average temperatures and high salinitythroughout most of the season during 1999 mayhave acted together to produce exceptionallyfavorable spawning conditions.

There was a noticeable increase in the numberof small oysters observed at all of the barssampled in both the Piankatank and GreatWicomico Rivers. This is promising for thoserivers in that it means survival of the 1999 spatwas relatively high. Given that seed/oysters wereremoved from several bars (see above for details),survival of the 1999 spat was probably even

higher than the numbers suggest. The numberof market oysters in the Piankatank Riverdecreased for the first time in five years. Thisdecrease was also probably a result of seed/oysterremoval during spring 2000. Over the pastseveral years, there has been a steady increase inoyster populations in both the Piankatank andGreat Wicomico Rivers (Mann, 2000). This maybe due to the building of three- dimensional reefs(beginning in 1993 in the Piankatank and 1996in the Great Wicomico). Studies of Palace BarReef in the Piankatank, showed that three-dimensional reefs enhance oyster survival (Mannet al., 1996). In another study of artificial oysterreefs in the Great Wicomico River it was foundthat broodstock enhancement on a reef, gives thereef a “jump start” in terms of producing a viable,active spawning oyster population (Southworthand Mann, 1998). The data collected in both thePiankatank and Great Wicomico Rivers over thepast few years tend to suggest that the first yearafter broodstock addition is the most productiveyear in terms of the amount of spatfall. However,with continued broodstock addition and oystershell plants in surrounding areas in subsequentyears, the reefs can produce favorable numbersof larvae and hence spat (in comparison to pre-reef/pre-broodstock conditions). The decreasein spatfall during 2000 is hopefully a reflectionof poor setting conditions (i.e. harmfulphytoplankton populations, low oxygen content,etc.) and not an indication that the artificial reefsare only capable of sustaining viable oysterpopulations for a few years. The historicalimplications of the success of oyster reefsthroughout the Chesapeake Bay region suggestthat spawning/setting conditions during 2000were simply poor.

On the positive side, there was a relatively lownumber of boxes bushel-1 at most of the barsduring 2000 when compared with 1999. During1999, as high as 58% of the total number ofoysters (live and dead) consisted of boxes,whereas 39% of the total was the highest recordedduring 2000. The relatively high numbers ofboxes observed in the Piankatank and GreatWicomico Rivers, especially in the upper reachesof the Piankatank, were most likely due to thedinoflagellate (P. minimum) bloom mentioned


earlier. In hatchery experiments bloom densitiesof P. minimum were shown to cause 100%mortality by day 14 of the bloom (Luckenbachet al., 1993). The overall number of spat boxesrecorded during 2000 decreased when comparedwith 1999, especially at Tow Stake in theMobjack Bay and Burton Point in the PiankatankRiver. In contrast to 1999, there were no spatboxes found with gastropod bore holes in themat Tow Stake. However at Burton Point, thepercentage of the total spat boxes found to havesmall holes in them remained relatively highsimilar to 1999. These holes were most likelycaused by the oyster drills Urosalpinx cinera andEupleura caudata which are common in thelower Chesapeake Bay. Both of these specieshave been shown to be voracious predators ofoyster spat causing mortality throughout most ofthe Chesapeake Bay up until the occurrence ofHurricane Agnes (1972) which wiped them outin all but the lower reaches of the James Riverand mainstem Bay (Carriker, 1955; Haven,1974). However, individuals of both of thesespecies and drill eggmasses have been found inrecent years in the mouths of the Piankatank andRappahannock Rivers, including some in boththe 1999 and 2000 dredge samples.


Figure D1: Map showing the location of the oyster bars sampled during the 2000 dredge survey.Numbers in the blown up maps of the Piankatank and Great Wicomico Rivers represent theclosed black circles on the big map.

James River: 1) Deep Water Shoal, 2) Mulberry Point, 3) Horsehead, 4) Point of Shoal, 5)Swash, 6) Long Shoal, 7) Dry Shoal, 8) Wreck Shoal, 9) Thomas Rock, 10) NansemondRidge.

York River: 11) Bell Rock, 12) Aberdeen Rock.

Mobjack Bay: 13) Tow Stake, 14) Pultz Bar.

Piankatank River: 15) Ginney Point, 16) Palace Bar, 17) Burton Point.

Rappahannock River: 18) Ross Rock, 19) Bowler’s Rock, 20) Long Rock, 21) Morattico Bar,22) Smokey Point, 23) Hog House, 24) Middle Ground, 25) Drumming Ground, 26) ParrotRock, 27) Broad Creek.

Great Wicomico River: 28) Haynie Point, 29) Whaley’s East, 30) Fleet Point.


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Figure D2: Map showing the location of the artificial oyster reefs in the Virginia portion of theChesapeake Bay.

Lynnhaven River: 1) Lynnhaven River Reef.

Lafayette River: 2) Hampton Boulevard Bridge Reef, 3) Tanner’s Point Reef.

Elizabeth River: 4) Western Branch Reef, 5) Craney Island Reef.

York River: 6) Felgate’s Creek Reef, 7) Amoco Reef.

Mobjack Bay: 8) Ware River Reef, 9) North River Reef, 10) East River Reef.

Piankatank River: 11) Palace Bar Reef, 12) Bland Point Reef, 13) Iron Point Reef, 14) Bur-ton Point Reef.

Rappahannock River: 15) Ferry Bar Reef, 16) Drumming Ground Reef, 17) Temple BayReef, 18) Parrot’s Rock Reef, 19) Mill Creek Reef, 20) Sturgeon Bar Reef, 21) Broad CreekReef, 22) Butler’s Hole Reef.

Great Wicomico River: 23) Shell Bar Reef, 24) Cranes Creek Reef.

Potomac River: 25) Yeocomico River Reef, 26) Coan River Reef.

Eastern Shore: 27) Pungoteague Creek Reef, 28) Fishermen Island Reefs.


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FIGURE D4A: JAMES RIVER OYSTER TRENDSOVER THE PAST 10 YEARS

(error bars represent standard error of the mean)

Wreck ShoalDry ShoalThomas RockNansemond Ridge

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FIGURE D4B: JAMES RIVER OYSTER TRENDSOVER THE PAST 10 YEARS


HorseheadPoint of ShoalLong Shoal

Deep Water ShoalMulberry Point

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FIGURE D5: COMPARISON OF OYSTER ABUNDANCE IN THE YORK RIVER AND MOBJACK BAY 1997-2000(error bars represent standard error of the mean)

1997 1998 1999 2000

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Bell Rock(York)

Aberdeen Rock(York)

Pultz Bar(Mobjack)

Tow Stake(Mobjack)


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FIGURE D6: YORK RIVER AND MOBJACK BAY OYSTER TRENDS OVER THE PAST 10 YEARS


Bell Rock (York)Aberdeen Rock (York)

Pultz Bar (Mobjack)Tow Stake (Mobjack)

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FIGURE D7: COMPARISON OF OYSTER ABUNDANCE IN THE PIANKATANK RIVER 1997-2000


1997 1998 1999 2000

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FIGURE D8: PIANKATANK RIVER OYSTER TRENDSOVER THE PAST 10 YEARS


Burton PointGinney PointPalace Bar

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FIGURE D10A: RAPPAHANNOCK RIVER OYSTER TRENDS OVER THE PAST 10 YEARS


Broad CreekHog HouseDrumming Ground

Middle GroundParrot Rock

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FIGURE D10B: RAPPAHANNOCK RIVER OYSTERTRENDS OVER THE PAST 10 YEARS


Morattico BarRoss RockSmokey Point

Bowling RockLong Rock

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FIGURE D11: COMPARISON OF OYSTER ABUNDANCE IN THE GREAT WICOMICO RIVER 1997-2000


1997 1998 1999 2000

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FIGURE D12: GREAT WICOMICO RIVER OYSTER TRENDS OVER THE PAST 10 YEARS


Fleet PointHaynie PointWhaley's East

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ACKNOWLEDGEMENTS

These monitoring programs required the assistance of many people, without whose contributionsthey could not have been successfully completed. We are deeply grateful to the following: ReinaldoMorales-Alamo for information regarding historical data. Mark Luckenbach, P.G. Ross, Alan Birch,and Brent Parks (VIMS Eastern Shore Laboratory) for deployment and examination of the EasternShore shellstrings. Sam Wilson, George Thomas, Wayne Reisner, and Bob Gammish for help withvessel operations. David Wiker for help making the shellstrings. Stephanie Haywood for help inthe field, examination of shellstrings, and data entry. Carol Tomlinson, Cindy Forrester, and GailReardon (VIMS, Department of Fisheries, Science Budget Office). VIMS Vessel Operations De-partment provided assistance with boat scheduling and operation throughout the year, namely GeorgePongonis (superintendent), Raymond Forrest, and Susan Rollins. Cliff Fisher from VIMS VehicleOperations Department provided assistance with truck scheduling and operation. James A. Wesson,Division Head, Conservation and Replenishment Division of the Virginia Marine Resources Com-mission for use of the vessel J. B. Baylor , for his assistance during the fall survey, and for reviewof this report. Alan Godshall and Vernon Rowe of the VMRC for their assistance during the fall1999 dredge survey. Katie Farnsworth (VIMS, Department of Physical Sciences) helped create themaps of the sampling areas.

REFERENCES

Andrews, J.D. 1983. Transport of bivalve larvae in James River, Virginia. J. Shellfish Res. 3(1):29-40.

Calvo, L.M. and E.M. Burreson, 2000. Status of the major oyster diseases in Virginia 1999: Asummary of the annual monitoring program. Virginia Marine Resource Report No. 00-2. 23 pp.

Carriker, M.R. 1955. Critical review of biology and control of oyster drills Urosalpinx andEupleura. Special Scientific Report: Fisheries No. 148. 150 pp.

Haven, D.S. 1974. Effect of Tropical Storm Agnes on oysters, hard clams, and oyster drills. In:The effects of Tropical Storm Agnes on the Chesapeake Bay estuarine system. ChesapeakeResearch Consortium Publication No. 27. 28 pp.

Haven, D.S. and L.W. Fritz, 1985. Setting of the American oyster Crassostrea virginica in theJames River, Virginia, USA: temporal and spatial distribution. Mar. Biol. 86: 271-282.

Luckenbach, M.W., K.G. Sellner, S.E. Shumway, K. Greene, 1993. Effects of two bloom-forming dinoflagellates, Prorocentrum minimum and Gyrodinium uncatenum, on the growth andsurvival of the Eastern oyster, Crassostrea virginica (Gmelin, 1791). J. Shellfish Res. 12(2): 411-415


Mann, R., F.O. Perkins, J. Wesson, and I.K. Bartol. 1996. Intertidal oyster reefs as a tool forestuarine rehabilitation and rejuvenation of the Virginia oyster fishery. Unpublished final reportsubmitted to the Department of Environmental Quality/Virginia Coastal Resource ManagementProgram, Richmond, VA.

Mann, R., 2000. Restoring the oyster reef communities in the Chesapeake Bay: A commentary.J. Shellfish Res. 19(1): 335-339.

Morales-Alamo, R. and R. Mann. 1998. The status of Virginia’s public oyster resource 1997.Molluscan Ecology Program, Virginia Institute of Marine Science, Gloucester Point, Virginia.Virginia Marine Resource Report No. 98-2. 49 pp.

Southworth, M and R. Mann. 1998. Oyster reef broodstock enhancement in the Great WicomicoRiver, Virginia. J. Shellfish Res. 17(4): 1101-1114.

Southworth, M., J.M. Harding, and R. Mann. 1999. The status of Virginia’s public oyster re-source 1998. Molluscan Ecology Program, Virginia Institute of Marine Science, GloucesterPoint, Virginia. Virginia Marine Resources Report No. 99-6. 37 pp.

Southworth, M., J.M. Harding, and R. Mann. 2000. The status of Virginia’s public oyster re-source 1999. Molluscan Ecology Program, Virginia Institute of Marine Science, GloucesterPoint, Virginia. Virginia Marine Resource Report No. 00-03. 38 pp.

Thompson, R.J., R.I.E. Newell, V.S. Kennedy, and R. Mann. 1996. Reproductive processes andearly development. In: The Eastern Oyster: Crassostrea virginica. V.S. Kennedy, R.I.E. Newelland A.F. Eble, (eds.). Maryland Sea Grant Publications, Maryland 722 pp.

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