Library

National Wetlands Research Center

U. S. Fish and Wildlife Service

700 Cajundow Boulevard

Lafayette, LB, 70506

Biological Report 82 (11.57)

July 1988

TR EL-82-4

Species Profiles: Life Histories and

Environmental Requirements of Coastal Fishes

and Invertebrates (South Atlantic)

AMERICAN OYSTER

QL

155

.S63

no. 82

11.57

Fish and Wildlife Service

U.S. Department of the Interior

Coastal Ecology Group

Waterways Experiment Station

U.S. Army Corps of Engineers

Blologlcal Report 82t11.57)

TR EL-82-4

July 1986

Species Prof I les: Life Hlstorles and Environmental Raqulrernents

of Coastal Fishes and Invertebrates (South Atlantic)

A)IIER I CAN OYSTER

bv

Victor G. Burrel I, Jr.

South Carolina Marine Resources

Research Institute

217 Ft. Johnson Road

Charleston, SC 29412

Pro Ject Manager

Carrel I Cordes

Project Off icer

David Moran

National Wetlands Research Center

U.S. Flsh and Wildllfe Service

1010 Gause Boulevard

SI ldel I, LA 70458

Performed for

Coastal Ecology Group

U.S. Army Corps of Engineers

Waterways Exper lment Stat Ion

Vicksburg, MS 39180

and

National Wetlands Research Center

Research and Development

Fish and Wildlife Service

U.S. Department of the Interior

Washington , DC 20240
This series can be referenced as fol lows:

U.S. Fish and Wlldlife Service. 1983-19_. Species prof lies: I Ife histories

and env I ronmental requl rements of coastal f lshes and Invertebrates. U.S.

Fish Wildl. Serv. Blol. Rep. 82(11). U.S. Corps of Engineers TR n-82-4.

This proflle can be cl-ted as follows:

Burrel I, V.G., Jr. 1986. Species prof I les: I Ife hlstories and enviromnental

requirements of coastal f lshes and invertebrates (South AtlantIc+AmerIcan

oyster. U.S. Flsh Wlldl. Serv. Biol. Rep. 82f11.57). U.S. Army Corps of

Englneers TR EL-82-4. 17 PP.
PREFACE

This species profile is one of a series on coastal aquatic organisms,

principally fish, of sport, commercial, or ecological importance. The profiles

are designed to provide coastal managers, engineers, and biologists with a brief

comprehensive sketch of the biological characteristics and environmental

requirements of the species and to describe how populations of the species may be

expected to react to environmental changes caused by coastal development. Each

profile has sections on taxonomy, life history, ecological role, environmental

requirements, and economic importance, if applicable. A three-ring binder is

used for this series so that new profiles can be added as they are prepared.

This project is jointly planned and financed by the U.S. Army Corps of Engineers

and the U.S. Fish and Wildlife Service.

Suggestions or questions regarding this report should be directed to one of

the following addresses.

Information Transfer Specialist

National Wetlands Research Center

U.S. Fish and Wildlife Service

NASA-Slide11 Computer Complex

1010 Gause Boulevard

Slidell, LA 70458

or

U.S. Army Engineer Waterways Experiment Station

Attention: WESER-C

Post Office Box 631

Vicksburg, MS 39180

iii

,

CONTENTS

FREFACE ................................

III

ONVERS ION TABLE ........................... I V

FIGURES ................................

v i

ACKNWLEDGMENTS ............................ vii

NOMENaAIJRE/TAXONoMY/RANGE ......................

MORPHOLOGY/IDENTIFICATION AIDS ....................

REASON FOR INCLUSION IN SERIES ....................

LIFE HISTORY .............................

Spawning .............................

Eggs and Ferti I ltatlon ......................

Spat ...............................

Adult ...............................

GROWTH l .

CCMMERCI;V’H;\R;EST* : : : : : : : : : : : : : : : : : : : : : : : : . .

Population Dynamics ........................

ECOLOGICAL ROLE. ...........................

ENV IRONMENTAL REQU IREMENTS ......................

Temperature ............................

Salinity .............................

Dlssol ved Oxygen .........................

Habltat. .............................

Other Environmental Factors ....................

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1

1

3

33

4

5

5

5

!

;

10

10

10

11

11

V
FIGURES

1 American oysters, Crassostrea y&@&a, fran subtldal and

intertidal habitats In the South Atlantic region. . . . . . . . 1

2 Dlstrlbotlon of predominantly subtidal and intertidal oysters

In the South Atlantic reglon. . . . . . . . . . . . . . . . . . 2

3 A typlcal intertldal oyster bar showing the dense growth

canmontothese areas. . . . . . . . . . . . . . . . . . . . . 3

4 Intertidal oysters being picked by hand . . . . . . . . . . . . 4

5 Oyster landlngs 1880-1984 for the Individual States and for

the reglon as a whole . . . . . . . . . . . . . . . . . . . . . 6

6 A mechanical intertidal oyster harvester being used to

rehabilitate public oyster grounds in South Carolina . . . . . 8

vi
ACKNOWLEDGMENTS

I thank Ronald Dugas and John Manzi for their reviews and many helpful

suggestions. I am grateful to Louise Hammes for typing the manuscript, Karen

Swanson for drafting the figures, and George Steele and William Anderson for

photographic assistance.

assistance.

Thanks also go to Nancy Peacock for computer

vii

SUBTIDAL I

INTERTIDAL

Figure 1. Amer lcan oysters, Crassostrea lnertldal m,from subtldal and

habitats in the South- Atlantic region.

AMER I CAN OYSTER

NOMENCLATURE/TAXONOMY/RANGE MORP!iOLOGY/IDENTIFICATION AIDS

Scientific name............-

- (Figure 1)

Preferred ccmmon name.........American

oyster

Other common names . . . . ..Eastern oyster

and when referrlng to long, thln

shel led C. vlralnfca grow 1 ng

Shel I welght and shape can be

hlghly varlable, ranging from heavy

shell and fairly regular In subtldal

single oysters to thin, elongated, and

highly irregular In intertldal oysters

(Figure 1). The left valve, which Is

attached to the substrate, Is usual ly

thicker and more deeply cupped than

the right. The adductor muscle scar

is located posteriorly and is generally pigmented; no hinge teeth are

present.

oyster,

%ely or her;

resemb I es

vIralnIx& but the muscle scar IS mot-i

central ly located and not general ly

colored, and smal I dentlcles are

present on elther sl de of the r lght

valve hinge. These dentlcles f It Into

correspond I ng depresslons In the

margin of the left valve. Qstrea

r

averages only about 5 cm In

and therefore

ccnuner~f al Interest.

is not of

It Is most often

found in higher sal lnlty (35 ppt) than

1 ntert I

Class...

Order...

Family..

dal I y, coon oyster

. . . . . . . . . . . . . . . . . . . ..Bivalvla

. . . . . . . . . . . . . . . . . . ..Pteroldea

. . . . . . . . . . . . . . . . . . ..Ostreldae

Geogr ap h I C range: Found in sounds,

bays , and estuar I es from New

Brunsw Ick, Canada, to the Gul f of

Mex I co. Throughout most of its

range, It grows subtldally;

however, In the South Atlantic

States from about the Newport

River, North Carol Ina, south along

the east coast of Florlda, It

occurs principal ly In dense,

IntertIdal beds (Figures 2 and 3;

Galtsoff 1964; Abbott 1974).

1
NORTH CAROLINA

_-- ‘.

.

SOUTH CAROLINA

2:. JACKSONVILLE

N SUBTIDAL

p?J INTERTIDAL

.ESTON

ATLANTIC OCEAN

MILES

0 5 0 100

KILOMETERS

8

43N

I

.

Figure 2. Distribution of predominantly subtidal and intertidal oysters in the

South Atlantic region.

2
Figure 3. A typical intertidal oyster bar showing the dense growth common to

these areas.

I;. w, but both species may

co-occur In salinities as low as 20-25

ppt (Menzel 1956; Yonge 1960; Galtsoff

and Merrill 1962; Galtsoff 1964;

Porter and Tyler 1974).

REASON FOR INCLUSION IN SERIES

The American oyster has been

explolted commercially since the

mid-19th century In the South Atlantfc

reglon and continues to support a

praninent flshery In North Carolina

and South Carolina (Burrell 1985a;

Figure 4). It is also an important

recreational species (Moore et al.

1984).

Vast intertidal reefs constructed

by oysters are slgniflcant

biologically and physical ly In at 16.4 OC in

estuaries of the South Atlantic 20.0 OC in more

reglon. F ishes, crabs and shrlmp are 25 OC in the Gul

among the anlmals that util lze the 1969). McNulty

intertldal reefs while they are South Carolina

3

Water temperature stimulates

gametogenesls and spawnlng In the

American oyster and crltlcal

temperatures vary over the

geographical range. Spawnlng begins

Long Island Sound,

southerly areas, and

f of Mexico (Loosanoff

(1953) reported that

intertidal oysters

submerged for refuge and also as a

source of food, foraglng on the many

reef dwelling species. Reefs, as they

become establlshed, modify tidal

currents and thls in turn affects

sedlmentary patterns. Further, the

reefs contribute to the stabillty of

stream bottoms and banks and to the

bordering marsh as well (Wells 1961;

Bahr and Lanler 1981; Cake 1983).

LIFE HISTORY
Figure 4. Intertidal oysters being

picked by hand. Ttsis is the chief

mean 5 of harvesting intertidal

oysters.

spawned wnen surface temperatures

ranged from 18.6 OC to 25 OC. Burrell

et al. (1984) found that both subtidal

and intertidal oysters were ripe

throughout the year. Spawning was

intermittent at salinities averaging

25 ppt or higher from May to November.

In a lower salinity area (less than 20

PPt), spawning of subtidal oysters

appeared to be restricted to one major

period in midsummer (temperature above

30 "C), while intertidal oysters

spawned during two major periods: one

in early summer (>30 "C) and one in

fall (>23 "C). Durant (1969) reported

that the spawning season in Georgia

lasted from May, when temperatures

reached 23 OC, to November. In

Apalachicola Bay, Florida, spawning,

indicated by the appearance of

;iung oysters on planted shell began

the second week of April when

temperatures reached 22.5-24.0 OC and

continued through the second week of

November. Mass spawning did not occur

until temperatures reached 26.0 OC

(Ingle 1951).

Spawnlng in females is triggered

by release of sperm into the water

column (Andrews 1979; Bahr and Lanier

1981). Oysters may spawn several

times during a season; intermittent

protracted spawning is typical in

intertidal oysters. A rapid increase

in temperature also often triggers

spawning in oysters (Hidu and Haskins

1971; Dupuy et al. 1977).

Intermittent spawning in intertidal

oysters may result frctn greatly

fluctuating temperatures on intertidal

reefs. Lunz (1960) reported

variations of 16 "C wlthln a few

minutes. Galtsoff (1964) estimated

one female discharged 114.8 million

eggs at a single spawning. Number of

eggs released varies with size and

condition of the female and number of

spawns (Galtsoff 1964).

and Fertillzat~

Eggs of Crassostrea v-kgln_b are

canpressed and pear-shaped measuring

from 55 to 75 pm in the long axis and

35 to 55 pmwlde (Gaitsoff 1964). Trochophore larvae develop within 6 to

9 h after egg fertilization, and

metamorphose into straight hinge or

veliger larvae at 12 to 16 h after

fertilization (Galtsoff 1964; Dupuy et

al. 1977). The straight hinge larvae

and subsequent stages are planktonic

and remain in the water column for up

to 3 weeks, with planktonlc time

varying with available food, water

temperature and salinity (Bahr and

Lanier 1981; Cake 1983). Oyster

larvae are transported throughout

estuarlne systems by tidal action.

Larvae concentrate near the surface on

rising tides and near the bottan on

falling tides, thus increasing their

chances of being more widely

distributed in an estuary and not

being swept out to sea (Carriker 1951;

Haskins 1964; Wood and Hargis 1971).

The final larval stage, called

the pediveliger or eyed larva, is

4
approxlmately 300 pm In diameter and

is characterized by a well-developed

foot and two eye spots. The foot

enables the larvae to crawl on the

bottan to seek substrate suitable for

attachment. The early sessile stage

of the oyster Is called spat and the

process of attachment Is called

setting or spatfall. The pedlvellger

may explore several sites before

permanently attaching the left valve

to the flnal substrate wlth cement

produced by a larval organ, the byssus

gland.

Pedivel lgers rapidly lose many

larval features after attachment. The

foot and eye spots are lost and the

velum Is Incorporated into parts of

the alimentary system (Galtsoff

1964). Attachment substrate may be

any hard substance such as glass,

concrete, bits of rock or other

shell. Oyster shell Is most often

chosen by the pedivellger. Oyster

planters distribute molluscan shell

called cultch for this purpose

(Burrell 1985b). Larval set Is

stimulated by increase In

temperature (Lut? et al. 1970;

Hldu and Hasklns 1971). Bahr and

Lanler (1981) reported that while

oysters tend to be photoposltlve

durlng larval stages, they may become

photonegatlve as water temperature

increases.

Heavlest spatfall may occur below

mean low water in the South Atlantic

States; however, survival IS much

greater at just above mean low water

(Chestnut and Fahy 1953; McNuIty

1953). Lower survival below mean low

water may be a result of predatlon or

of fouling by competitors and currentborne silt (Dean 1892; Chestnut and

Fahy 1953; McNulty 1953; Linton 1969).

Once attached, oysters remain In

the same locatlon throughout life

unless they are moved by man. In the

South Atlantic States, oysters (with

only a few exceptlons) occur In

Intertidal beds that become

established when conditions permit;

that Is, when sallnlty, current, food,

supporting substrate, and turbidity

are suitable (Burrell et al. 1981;

Cake 1983). These beds provlde

habitat for numerous estuarlne animals

(Wells 1961; Dame 1972, 1979; Bahr and

Lanler 1981; Cake 1983; Manzl et al.

1985). Stream channels are Influenced

by oyster reefs, which serve as elther

a stabilizing Influence or modifying

force as these reefs grow. Subtldal

oyster beds do occur naturally but

rarely In Southeastern States and

provide habitat for other shellfish

such as hard clams, Mercenar

mercenarfa (Burrell 1977).

Adult oysters are usually

dioecious, but sex changes are

frequent. Generally, yearling oysters

are predcmlnantly males, but older

oyster populations become

preponderantly females. Even In

oysters several years old, however,

sex reversals are common and females

may become males again or vice versa

(Galtsoff 1964).

GRCWTH

Ingle (1950) found that growth

of American oysters in Florida

exceeded 100 mm in 31 weeks; growth in

length was greates.t in the first 6

weeks after setting. Palmer (1976)

recorded increases in average length

of Georgia oysters over a 7-month

period (November to June): in

subtidal and intertidal animals,

increases were 31.1 mm and 19.6 mm,

respectively, when beginning sizes

were lo-19 mm and 10.2 mm; subtidal

oysters grew 3.0 mm when beginning

size was 100 mm. Manzi et al. (1977)

and Burrell et al. (1981) reported

monthly growth of 1 to 4 mm in South

Carolina oysters. Growth is continuous throughout the year, as far north

as South Carolina, although it slows

appreciably in midwinter in South

5
Carolina (Burrell et al. 1981).

Growth appears to be most rapid in

summer (Ingle 1950).

Growth appears to be greater In

subtldal oysters than In IntertIdal

oysters; however, this may be a result

of crowding on lntertldal beds

(Burrel I 1982). Gil lmor (1982) found

that oyster growth was better per unit

immersion time at sane depths below

mean hlgh water In the Intertidal zone

than In subtldal beds. Protracted

spawnlng seasons may also retard

growth In Intertidal oysters because

of energy demands for this actlvlty

(McNulty 1953). Lunz (19551, Anderson

(19761, and Manzi et al. (1977) found

that growth In salt ponds exceeded

that In adJacent waterways.

COMMERC I AL HARVEST

The oyster Industry has provided

employment for many watermen In the

South Atl antlc States (Magglonl and

Burrel I 1982). In the early 1900’s,

annual I and1 ngs general ly exceeded 10

ml I I Ion pounds and peaked at nearly 20

mll I Ion pounds In 1908. Productlon

then declined steadily until 1970.

From the mid-1970’s to 1984, landings

remained fairly steady at about 2

mill Ion pounds (Burrell 1982, 1985a;

Figure 5). Several pr I ncl pal causes

of this decl lne have been suggested:

1. Loss of I abor to ccnnpetl ng

Industries.

2. Grow I ng area lost to

product ion because of pol I utlon,

changes In sal I nl ty patterns caused by

coastal development and changes In

farming and forestry practices.

3. Management practices that do

not encourage good husbandry.

4. Lack of modern technology ln

cu I ture, harvest and processing

sectors.

- SOUTH ATLANTIC REGION

**...*** SOUTH CAROLINA

- -NORTH CAROLINA

- - --GEORGIA

-*.-EAST COAST OF FLORIDA

I890 1900 1910 1920 1930 1940 1950 1960 1970 1980

Figure 5. Oyster landings 1880-1984 for the individual States and

for the region as a whole (Fishery Statistics of the United States,

1880-1979 : fishery statistics offices for --- Statesinvolved,

1980-1984).

6
/

k 5. Laws that do not encourage

Increased Investment in the Industry,

6. Final ly, and probably most

importantly, the I ack of markets for

the lntertldal oyster. This shel I fish

does not lend Itself to raw shucking

and must therefore be opened chiefly

by steam. The meats are then canned

as a cooked product that has a very

I Im lted demand and must compete with

cheap Imports. The number of

canner Ies has dropped 1 n South

Carol Ina al one from 16 in 1905 to one

today (Keith and Gracy 1972). The

other vlable market for intertidal

oysters Is sales to lndivlduals or

groups for oyster roasts. These

roasts are traditional coastal social

events and offer I lttle potential for

expand Ing the market.

L,

Biological prob I ems such as

disease, recruitment fal I ure, and

predators 1 nf I uence product ion of

southern intertldal oysters less than

northern subtldal stocks. An

overabundance of set and high survival

Is a greater problem for the southern

oyster grower. The intertidal reefs

tend to become overgrown w 1 th smal I

and densely crowded oysters. Llm lted

markets compound the problem because

many more oysters are ava I I abl e on

reefs than can be sold and, therefore,

the reefs are not harvested regular1 y.

Oyster meat yield per volume of

she1 1 stock is lower in the South

Atlantic States than in other oystergrowing areas because of the poor

condition of the oysters due to a

protracted spawning season, and

because the crowded oysters in the

intertidal zone are small, elongate,

and thin shelled. Yield in Virginia

oysters averaged 6.0 to 6.5 pints/

bushel raw shucked, while in South

Carolina canneries the yield was only

about 1 pint per bushel (Lunz 1950).

Each State of the South Atlantic

region has a program of some sort

deslgned to revltal Ize their oyster

Industry (Cowman 1982; Magglonl and

Burrel I 1982; Munden 1982).

Mechanlcal harvesters are belng used

in North and South Carol Ina to move

oysters fran areas closed to

harvestlng and from very dense beds to

publ Ic grounds In order to improve

stocks In these areas. (Figure 6;

Munden 1982; Manzl et al. 1985).

latlon L&nam&

Sel lers and Stan I ey (1984)

rev I ewed mortal Ity of larvae In

subtldal growing areas. They noted

that mortal Ity varies great I y

accord1 ng to area, vul nerabl I I ty to

predators and intensity of set.

Ne I son (1925) noted that I obate

ctenophores fed on oyster larvae and

that abundance of ctenophores was

Inversely correlated wlth abundance of

oyster set In New Jersey waters. Spat

mortallly Is not a problem In the

southern IntertIdal oyster; invariably

more spat survive than are needed to

repopul ate reefs and, as mentioned,

overcrowdlng and poor growth result.

Mortal lty of spat In North Carol Ina

and South Carol Ina 1 ncreased w I th

depth belcu mean low water (Chestnut

and Fahy 1953; McNu I ty 1953).

McKenz le (1981) calculated surv lval

rates based on year1 y changes In

popul atlon; initial approxlm?te spat

density was 200 to 10,000/m , at 1

to 2 years numbers fel I to 300/m2,

and at 3 to 4 years only 75/m2

remalned. Burrel I et al. (1981)

observed in trays at several I ocat ions

In South Carol lna that year I y

mortal ltles exceeded 50% In seed

oysters 2 years old at transplanting

and less than 22% tn seed 1 year 01 d

at transplanting. In another study

of South Carolina oysters (Manzi et

al. 1977)) adult oysters planted

subtidally had survival rates of 85%

to 91% in salt ponds and 92.5% to

94.5% in adjacent streams. Reisinger

(1978) reported monthly mortalities

ranging from less than 5% to 40% in a

Georgia intertidal bed.

ECCLOG I CAL ROLE

Larvae are pl ankt ivores feed1 ng
Figure 6. A mechanical intertidal oyster harvester belng used to rehabil itate

public oyster grounds in South Carolina.

principal ly on smal I naked flagel lates

and diatoms. Detrltal particles and

bacteria associated wlth particles,

and possibly, dlssolved organic

canpounds, may also be of nutritional

importance to oyster larvae (Gal tsoff

1964; Bahr and Lanler 1981; Cake

1983). Larvae are in turn consumed by

a I arge number of predators that

lncl ude copepods, ctenophores,

jel lyf I sh and the young of f 1 sh and

crustaceans (Nelson 1925; Andrews

1979).

Adult oysters also feed prlmarlly

on phytopl ankton. Preferred slze of

naked f I agel I ates sel ected by oysters

was reported by Haven and

Morales-Alamo (1970) to be 3 to 4 urn.

Under optimal condltlons o f

temperature and sal 1 nl ty, an oyster

pumps water at the rate of 15 I/h.

(Galtsoff 1964). The da1 I y vol ume of

water f i I tered by intertidal oysters

1s not known, but presumably it Is

less than that of subtldal oysters for

no other reason than lntertldal

oysters may spend half their I lves out

of water. The extensive sal t marshes

border 1 ng tidal creeks serve as

nutrient and organic detritus sinks

and thelr flushlng provides a rich

food source for oysters (de la Cruz

1973; Manzl et al. 1977).

lntertldal oyster reefs provide

habitat for countless 1 nfaunal and

eplfaunal species. Wel Is (1961)

I lsted 303 species fran both

intertldal and sub-tidal reefs ln North

Carol lna; Bahr (1974) reported some

42 species or groups associated wlth

intertidal reefs In Georgia; and Dame

(1979) found 37 species and Manz I et

al. (1985) listed 89 species for South

Carol i na intertidal reefs. Dame

(1979) reported the average number of

8
L Indlvlduals/m2 to be 2 949, and Bahr

(1974) 24, 747/m2 o; assoc 1 ated

animals I ivlng on intertidal oyster

reefs In South Carol Ina and Georgia,

respectively. Reefs al so Intercept

tidal currents and may profound I y

affect the sultabil lty of adJacent

areas for other species.

The density of oysters growlng in

intertidal reefs almost def les

canprehension. Lunz (1960) counted

5,895 oysters, 05 4.5 U.S. bushels, In

an area of 1 yd . In another study,

he reported an average of 135.9 2-Inch

oysters per square yard In 117 samples

(Lunz 1943). Bahr and Lanler (1981)

estimated that oysters al one accounted

for approximately 87.5% of the biomass

and 48.1% of the resplratlon on an

oyster reef. Lunzrs (1943, 1960)

est I mates suggest that this value

appears reasonab I e.

k

Many theories have been put forth

to explain the success of intertidal

oysters in the South Atlantic States

and the lack of success of subtidal

oysters. These include avoidance of

predators such as dr I I Is (&pleura

F& =TrZlii;:

crabs (Cd ;p. and family

Xanth I dae), starf I sh

E8

f’_(E

f I al-worms

(Sty locus &I lptlc~) (Battle 1892;

Carrlker 1955; Lunz 1960; Merriner and

Smlth 1979; Bahr and Lanier 1981;

Sel lers and Stanley 1984). Bor I ng

sponges (CI spp.) and annelid

worms ( Polydor;a;i;,), which cause

considerable t o subti da1

oysters, are not a problem in the

intertidal zone (Lunz 1947).

Other reasons that may account for

oyster reef concentrat I ons in the

IntertIdal zone are the presence of

more suitable substrates, more

available food, less turbldlty, more

suitable current velocftles,

spatfal I,

h lgher

exclusion of some

disease-causing organlsms, and genetlc

differences leadlng to physiologlcal

selection (Lunz 1941, 1943; Haven and

Burrel I 1982; Burrel I et al. 1984).

Recent studles have shed I ight on two

of these conjectures. No ev I dence of

genetlc differences between subtidal

and lnterfldal oysters from the same

South Carol Ina river system was

determlned In an electrophoretlc study

by Anderson and Wel r (W. W. Anderson,

Department of Molecular and Populatlon

Genetlcs, Unlverslty of Georg I a,

Athens; pers. canm.). Burrel I et al.

(1984)

Intensity

lntertlda

magnitude

Carolina;

appear -t

f

0

ound the lncldence and

of lnfectlon of subtldal and

oysters by the pathogen

a to be of the same

In two areas of South

thus this disease did not

be influenced by habitat

el evat Ion. Other oyster d I seases, such

as Delaware Bay disease caused by the

haplospor idean mti and

seas 1 de d I seas8 caused by the

hapl ospor idean M. al-al have not Is

been reported south of North Carol ina

along the Atlantic coast.

Subtldal oysters compete for

grow I ng space w lth barnacles (Balanus

spp. 1, scorched mussel (Brachfodontes

-1, ribbed mussel (Geukensla

Z$Z.

and Jingle shel I (Ananla

The distribution of

I ntertl dal oysters does not appear to

be affected by these organisms (Dame

1970).

ENV I RONMENTAL REQU I REMENTS

The eastern oyster Is a very

successful estuarlne animal and, as

such, It tolerates widely varying

sal Inities, temperatures, currents and

turblditles (Andrews 1979). The

Intertidal oyster thrlves In the most

r I gorous of habltats (Lunz 1960).

To I erance t o extremes of one

env I ronmental condltlon IS often

mod 1 f ied by lnteractlon of another

condltlon such as an oyster’s abll Ity

to survive low sal fnfty in cold

weather (Andrews et al. 1959). It is,

therefore, difficult to precisely

def Ine environmental requirements.

9
requires temperatures above 

As a general rule, C. w

19.5”C for

egg development. Larvae develop

properly above 20 ‘C and adults grow

at temperatures 10 to 30 OC or higher

(Gaitsoff 1964; Burrel I 1985b).

Southern I ntertl dal oysters are abl e

to w l-i-hstand summer temperatures above

43 OC when exposed to the sun and then

sudden drops to 26 OC when the tide

again covers the bed (Lunz 1960).

Oysters are also exposed to wlnter alr

temperatures that may fal I below

f reez I ng ; even when these oysters are

exposed several hours to these

extremes, they apparent1 y tolerate

them wel I. However, mortal Ity In

several oyster beds In the

McClellanville, South Carolina, area

was almost 100% when air temperatures

sudden1 y dropped 19 “C in 24 h after

several weeks of above normal ralnfal I

(Purv is 1983). The 1982 cold wave was

the most severe for December In South

CarolInaIs hlstory, but lower than

norma I sal tnlty caused by heavy

ralnfal I may al so have been a

contributing factor to thls

mortality. Oyster growers In the area

reported deaths from freez Ing were

most unusual In these beds.

Inltv

Castagna and Chanley (1973) In a

review of salinity requirements for

I I fe stages of oysters reported that

egg cleavage occurred at 7.5 to 35 ppt

with optimal development at 10 to 22

ppt, larvae developed at 5 to 39 ppt,

and growth was best at 25 to 29 ppt.

Metamorphosls occurred between 5.6 and

35 ppt. Spat grew best at sal initles

of 15 to 26 ppt (Chanley 1957). Adult

oysters were produced commercial ly In

Florlda In areas where the sal lnlty

var led from 0 to 42.5 ppt (lngle and

Dawson 1950). Growth Is most

favorabl e at 14 to 30 ppt (Castagna

and Chanley 1973).

Heavy ral ns In the watersheds of

r I vers feed I ng estuar I es may on

occas I on cause catastrophic kl I Is.

This may be associated with troplcal

storms or h lgher than usual spr I ng

ralns (Andrews et al. 1959; May 1972;

Haven et al. 1976; Burrel I 1977).

lntertldal oysters In the South San-tee

Rlver, South Carol Ina, suffered higher

losses as a consequence of Icw

sal lnlty than dld subtldal oysters In

the same system. This would be

expected because surface water would

tend to be less sal Ine than bottcm

water and intertldal oysters would be

subject to fresher water for a longer

per fod. However, mortal lties among

subtldal and lntertldal oysters were

near identical In an adjacent estuary

at the same time (Burrel I 1977).

Oysters died from lack of oxygen in

the James River, Virglnla, In winter

and early spr I ng 1979-80 because

freshwater cover I ng the beds prevented

the animals from feeding and respiring

(Andrews 1982). Th Is appears to be a

fairly regu I ar phenomenon In the

Rappahannock River, Vlrglnla, in wet

years (Haven et al. 1976; Andrews

1982). Moderate sal lnitles (those

less than 15 ppt) for a sfgnlficant

per I od during the year may be

benef lcial in that most predators are

excluded or thelr numbers greatly

reduced and sane dlsease organisms are

kept out or their virulence Is

marked I y weakened In these areas

(Haven et al. 1978; Burrel I et al.

1981).

lved w

Oysters are tol erant of low

d lssol ved oxygen, surviving at

concentrations as low as 1 ppm

(Andrews 1982). In I aboratory

studies, I arvae ceased to SW lm and

died after 3 days when oxygen

concentration was 0.1 ppm and young

spat died wlthln a week; however,

adult oysters survived much longer at

the same concentration (Haven et al.

1978). Hourly oxygen uptake Is low in

oysters, 15.5 cc/kg dry wt., as would

be expected for a sedentary animal

(Nlcol 1960). Furthermore, oysters

probably use less than 10% of the

10
L oxygen aval lable In the feed 1 ng

currents passing over their gills

(Galtsoff 1964).

itat

L,

The preferred habitat for oysters

In the South Atlantic reglon Is fran

just below the mean low water level to

about 1 m above mean law water

(Sandlfer et al. 1980). If al I other

conditions are suitable, a flrm bottan

is not necessary for a reef to become

estab I I shed. A few oysters may attach

to a bit of she1 1 or wood in a mudflat, and other oysters attach to

them, push1 ng them into the mud and

smother I ng them but providing

substrate for subsequent spat. This

process continues until the flrst set,

long since dead, sf nks deep enough

Into the mud to reach a sufficiently

flrm stratum to prevent further

subs1 dence. Shel Is growlng on top of

the buried she1 I reach the surface of

the mud and provtde attachment area

for subsequent crops of oysters. The

reef then expands from this

beglnnlng. The under I y I ng matr Ix

supporting reefs Is fairly fragile In

pl aces and Its lntegr Ii-y can be

damaged by heavy harvest1 ng gear.

Water currents must be strong enough

to provlde food. (GaItsoff (1964)

estlmated that water pass1 ng over an

oyster reef should be renewed 72 times

In a 24-h period.) Al so, currents

must wash away sediments and

blodeposits of animals InhabIting the

reef (Haven and Morales-Alamo 1966).

Currents of too great a velocl ty can

Interfere w Ith feedIng and cause

structural damage (Gal tsof f 1964).

Planting she1 I to establ Ish an

lntertldal oyster reef can be a futile

exercise In many cases because the

she1 I may serve as a baf f I e In the

current and col lect sediment and that

results In rapld silting over (Smith

1949).

ather

A

Fnv

fairly

V

I arge tidal range

increases the lnterti dal area in the

South Atlantic States because of

I lttle relief In coastal areas. This

tide range is from about 1.5 to 2.1

m. These tides provide a mechanfsm

for f lushlng adjacent marsh areas and

enr 1 ch I ng the oys te;;yjowi ng water

(Man21 et al. Because

turbldlly Is hlgh if; southern

estuaries, phytopl ankton productlon Is

canparatlvely low; consequently marsh

contrlbutlon to oyster nutrltlon Is

probab I y much more important here

(Man21 et al. 1977).

Oysters, while tolerant of fairly

turbid water, decrease pump 1 ng rate

wlth Increase in slit concentrations

above 1 .O g/l and death may occur

after long-term exposure. Egg

survival was only 73% In water wlth a

sl It concentration of 0.25 g/l, and at

0.75 g/l growth of I arvae was

significantly affected (Loosanoff and

Tanmers 1948; Loosanof f 1962).

11

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13
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15
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PP.

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209 pp.

17
TRE6i3RT OOCUMENTATION 1. RE~R’ wo.

PAGE Biolooical Reoort 82t11.57)

4. fitI* .nd S,,btitl.

Species Profiles: Life Histories and Environmental Requirements

of Coastal Fishes and Invertebrates (South Atlantic) -- American

Oyster

7. *uihor(*)

Victor G. Burrell, Jr.

i. hr(ormins OrS*ni*ation Nwna and Addr**l

0. Pwform~nS OrS.niz*tion R.p,. II

10. Pmwctlla~klWork Unit No.

Nationai Wetlands Research Center U.S. Army Corps of Engineers

Fish and Wildlife Service Waterways Exneriment Station

U.S. Denartment of the Interior P. 0. Box 631

Washington, DC 20240 Vicksburg, ??S 39180

I* TYm of R*ooOR L Pwiod C0v.n

14.

II Supplemantmy Notes

*U.S. Army Corps of Engineers Report No. TR EL-82-4

1a *br*nti o&lit z?o rords)

Species profiles are literature summaries of the taxonomy, morphology, range, life history.

and environmental requirements of coastal soecies. They are designed to assist in

environmental impact assessment. The American oyster, Crassostrea virginica, is an

imnortant commercial and recreational species. Snawning occurs continuously in warmer

months. Larvae are planktonic and are distributed throughout estuaries by tidal currents.

After a Z- to 3-week olanktonic stage, larvae permanently attach to a solid substrate.

In the South Atlantic region, this solid substrate is usually the shell of other oysters

growing in the intertidal zone. This gregarious behavior results in formation of massive

intertidal reefs that are a prominent feature of high salinity bays, creeks and sounds in

the region. These reefs serve as habitat and foraging grounds for other species. Oysters

tolerate salinity from about 5 pot to above 40 pnt and temperatures from below freezing to

nearly 50°C.

17. Docum*nt Analysis l . b.sccriptc.rr

Estuaries Life cycles Oxygen

Oysters Feeding habits Suspended sediments

Growth Temperature

Feeding Salinity

b. IdwMiwsl~n.Endcd I.rms

American oyster Temnerature requirements

Crassostrea virginica Spawning

Salinity requirements

Unlimited Release

Unclassified I---- 17 - -

20. Securiw Class Vhir P-46 22. Price

Unclassified

Poe ANSI-239.10 OVTIONAL FORM 272 (C7

(Formerly NTtFL35)

Oepmtnwnt d Commrrc*
TAKE PRIDE

212 Amerzcd

DEPARTMENT OF THE INLERIOR

U.S. FISH AND WIlDLIFE SERVICE

As the Nation’s principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes

fostering the wisest use of our land and water resources, protecting our fish and wildlife,

preserving thaenvironmental and cultural values of our national parks and historical places,

and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in

the best interests of ail our peobie. The Department also has a major responsibility for

American Indian reservation communities and for people who live in island territories under

U.S. administration.