Do Not Remove frqm the Library U. S. Fish and Wildlife Servi~e - - -

n

FWSIOBS-82111.23 Narlona~ 1 \ b 3 b w ~ ;

JUIY 1984 700 Cajun Dome Boulevard TR EL-82-4

Lafayette, Louisiana 70506

Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic)

Fish and Wildlife Service Coastal Ecology Group

Waterwavs Ex~eriment Station U.S. Department of the Interior U.S. Army Corps of Engineers

FWS/OBS-82/11.23 TR EL-82-4 J u l y 1934

Species P r o f i l e s : L i f e H i s t o r i e s and Envi ronmenta l Requirements o f Coas ta l F i shes and I n v e r t e b r a t e s

(No r t h A t l a n t i c )

AMERICAN OYSTER

Mark A. S e l l e r s Program i n Oceanography

U n i v e r s i t y o f Maine a t Orono I r a C. D a r l i n g Cen te r

Walpole, ME 04573

and

Jon G. S tan l ey Maine Coopera t i ve F i s h e r y Research U n i t

313 Murray H a l l U n i v e r s i t y o f Maine

Orono, ME 04469

P r o j e c t Manager L a r r y Shanks

P r o j e c t O f f i c e r Norman Benson

Na t i ona l Coasta l Ecosystems Team U.S. F i s h and W i l d l i f e S e r v i c e

1010 Gause Bou levard S l i d e l l , LA 70458

Performed f o r Coas ta l Ecology Group

Waterways Exper iment S t a t i o n U.S. Army Corps o f Engineers

Vicksburg, MS 39180

and

Na t i ona l Coasta l Ecosystems Team D i v i s i o n o f B i o l o g i c a l Se rv i ces

Research and Development F i s h and Wi ld1 i f e S e r v i c e

U.S. Department o f t h e I n t e r i o r Was h i ng ton, DC 20240

Th is s e r i e s should be referenced as f o l l o w s :

U.S. F ish and W i l d l i f e Serv ice. 1983-19-. Species p r o f i l e s : 1 i fe h i s t o r i e s and environmental requ i rernents o f coas ta l f i shes and i nve r teb ra tes . U.S. F i sh W i l d l . Serv. FWS/OBS-82/11. U.S. Army Corps o f Engineers, TR EL-82-4.

Th is p r o f i l e should be c i t e d as f o l l o w s :

Se l l e r s , M.A., and J. G. Stanley. 1984. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requ i rements of coas ta l fi shes and i n v e r t e b r a t e s (No r th At1 an- t i c ) -- h e r i c a n oys te r . U.S. F ish Wi ld l . Serv. FWS/OBS-82/11.23. U.S. Army Corps of Engineers, TR EL-82-4. 15 pp.

PREFACE

Th is species p r o f i l e i s one of a se r i es on coas ta l aqua t i c organisms, p r i n c i p a l l y f i sh , of spor t , cornmerci a1 , o r ecol og i c a l importance. The p r o f i l es a re designed t o p rov ide coas ta l managers, engineers, and b i o l o g i s t s w i t h a b r i e f zo~nprehensive sketch o f the b i 01 og i c d l c h a r a c t e r i s t i c s and envi ronrnental requ i re - ~nents o f t he species and t o descr ibe how popu la t ions of the species may be expected t o r e a c t t o environmental changes caused by coas ta l development. Each p r o f il e has sec t ions on taxonomy, 1 i f e h i s t o r y , ecol og i c a l r o l e , env i ronrnental requirements, and economic importance, if appl i c a b l e. A t h r e e - r i n g b inde r i s used f o r t h i s se r i es so t h a t new p r o f i l e s can be added as they are prepared. This p r o j e c t i s j o i n t l y planned and f inanced by t he U.S. Amy Corps o f Engineers and the U.S. F ish and W i l d l i f e Service.

Suggestions o r quest ions regard ing t h i s r e p o r t should be d i r e c t e d to :

I n fo rma t i on Trans fer Special i s t Nat iona l Coastal Ecosys terns Teatn U.S. F ish and W i l d l i f e Serv ice NASA-Sl i d e l 1 Computer Compl ex 1010 Gause Boul evard Sl i d e l 1, LA 70458

U. S. Army Engineer Waterways Experiment S t a t i o n A t ten t i on : WESER Post O f f i c e Box 631 Vicksburg, MS 39180

iii

CONTENTS

Page

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONVEKSIONTABLE v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AC KNOW LEUGMENTS v i

. . . . . . . . . . . . . . . . . . . . . . . . NOMEIJC LATUREITAXONOMY /RANGE 1 flORPHOLOGY /IDENTIF ICATION A1 DS . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . REASON FOR IIKL(JS1OW I ? 4 SERIES 2 LIFE HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Spaming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Larvae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Juven i l es 3 Adu l t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

GROWTH CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . 4 COMMERCIAL HARVEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Popul a t i o n Dynd.nics . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ECOLOGICAL ROLE 8 . . . . . . . . . . . . . . . . . . . . . . . . EI4VIRONlrlENTAL RE()UIREMENTS 8 Tellper-d t u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 S a l i n i t i e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 :iL1bi t a t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Other Env i ronrnental Fac to r s . . . . . . . . . . . . . . . . . . . . . . . 10

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

CONVERSION FACTORS

M e t r i c t o U.S. Customary

Mu1 t i p l y & To Ob ta i n

mi 11 i n e t e r s (mm) c e n t i r i e t e r s (cm) mete rs (m) k i 1 one te r s ( kn)

square mete rs (m 2, 10.76 square k i 1 o~ne te rs ( km2) 0.3861 hec ta res (ha) 2.47 1

l i t e r s ( 1 ) c u b i c mete rs (m3) c u b i c n e t e r s

i n ches inches f e e t m i l es

square f e e t square m i l e s acres

ga l 1 ons c u b i c f e e t a c r e - f e e t

m i l 1 i gratns (ng) 0.00003527 ounces grams ( g) 0.03527 ounces k i l og rams (kg ) 2.205 pounds m e t r i c tons ( t ) 2205.0 pounds m e t r i c t o n s 1.102 s h o r t t ons k i l o c a l o r i e s ( k c a l ) 3.968 B r i t i s h thermal u n i t s

Cel s i u s degrees 1.8(C0) + 32 Fahrenhe i t degrees

U.S. Customary t o M e t r i c

inches 25.40 inches 2.54 f e e t ( f t ) 0.3048 f a t homs 1.829 m i l e s ( m i ) 1.609 n a u t i c a l n i l e s (nmi) 1.852

square f e e t ( f t 2 ) acres square m i l e s (m i2 )

g a l l o n s ( g a l ) c u b i c f e e t ( f t 3 ) a c r e - f e e t

ounces (02) 28.35 pounds ( I b ) 0.4536 s h o r t t o n s ( t o n ) 0.9072 B r i t i s h the rma l u n i t (BTU) 0.2520

m i l 1 ime te r s cen t ime te r s meters meters k i l o n e t e r s k i l ometers

square meters hec ta res square k i l o n e t e r s

1 i t e r s c u b i c mete rs c u b i c meters

grams k i 1 ograms m e t r i c t ons k i l o c a l o r i e s

Fahrenhe i t degrees 0.5556(F0 - 32) Ce l s i us degrees

ACKNOWLEDGY ENTS

We thank Dr. Herbert Hidu, Professor of Zoology, University of Maine, f o r reviewing the manuscript and offering many helpful suggestions.

Figure 1. American oys te r f rom We1 l f l e e t Harbor, Massachusetts (Gal t s o f f 1964).

AMERICAN OYSTER

S c i e n t i f i c name . . . . . Crassostrea v i r a i n i ca (Gmel i n - .

~ r e f e r r g d common name . . . American oys ter (F igure 1 )

Other common name . . . Eastern oys te r Class . . . . . B i v a l v i a (Pelecypoda) Order . . . . . . . . . . . Pteroidea Family. . . . . . . . . . . Ostreidae

Geographic range : I n es tuar ies , drowned r i v e r mouths, and behind b a r r i e r beaches along t h e east coast o f North America, f rom t h e Gulf of St. Lawrence, Canada, t o Key Biscayne, F lo r i da . I n t h e G u l f o f Mex ico t o t h e Yucatan Peninsula o f Mexico, and i n t h e West Ind ies t o Venezuela. I n t r o - duced t o Japan, Aus t ra l i a , Great B r i t a i n , Hawaii, and t h e west coast o f North America (Ahmed 1975). The 1 argest American oys te r popu la t ions a re i n t h e Gul f o f Mexico, Chesapeake Bay, and Long I s l a n d Sound.

MORPHOLOGY/IDENTIFICATION AIDS

The l e f t valve i s almost always t h i c k e r and heav ier than the r i g h t , and more deeply cupped (Yonge 1960; G a l t s o f f 1964). The oys te r i s cemented t o t h e subs t ra te on i t s l e f t valve. Hinge t e e t h are absent, bu t a bu t t ress on t h e r i g h t valve f i t s i n t o a depres- s ion on t h e l e f t . There i s no gap be- tween t h e valves when f u l l y closed.

She1 1 shape i s var iab le . On hard bottoms, beaks (umbones) usual l y a re curved and p o i n t toward t h e pos te r io r , whereas i n s i l t y environments o r on reefs, umbones a re u s u a l l y s t r a i g h t . Sing1 e oys ters from hard subst ra tes are rounded and ornamented w i t h r a d i a l r idges and f o l i a t e d processes, whereas those from s o f t substrates o r ree fs are more s lender and are sparsely o r - namented. She1 1 th ickness a l so depends on envi ronment. Oysters on hard sub- s t r a t e s have t h i c k e r and l e s s f r a g i l e s h e l l s than those on s o f t substrate. The index o f shape (he ight + w id th1

l e n g t h ) v a r i e s f r o m 0.5 t o 1.3 i n sou thern p o p u l a t i o n s and f r o m 0.6 t o 1.2 i n n o r t h e r n popu la t i ons .

Growth r i n g s a r e ova l w i t h g r e a t - e s t growth a l ong t h e do r sa l - v e n t r a l ax i s . The p r i n c i p a l growth a x i s i s n o t permanent and may change s e v e r a l t imes over t h e l i f e s p a n of an i n d i v i d u a l , r e s u l t i n g i n a z i g z a g p a t t e r n . The growth a x i s may change as much as 90". Oys te rs 3 t o 5 y e a r s o l d a r e u s u a l l y 10 t o 15 cm i n h e i g h t . A l though t i s s u e mass reaches an upper l i m i t , t h e s h e l l con t i nues t o grow ove r t h e l i f e s p a n o f an o y s t e r (S tenze l 1971). The l a r g e s t h e i g h t r e p o r t e d i n t h e No r t h A t1 a n t i c r e g i o n i s 35.5 cm, f r om t h e Damaris- c o t t a R i ve r , Maine ( G a l t s o f f 1964).

The American o y s t e r i s i somya r i an (adduc to r muscles a r e equal i n s i z e ) . The i n t e r i o r o f t h e s h e l l has a p u r p l e -p i gmented adduc to r muscle s c a r s i t u a t e d s l i g h t l y p o s t e r i o r and ven- t r a l . A s e c o n d m u s c l e s c a r , o f t h e quens ted t muscle, i s s i t u a t e d under t h e hinge. Chalky d e p o s i t s may occur on t h e i n s i d e o f t h e s h e l l . The ad- d u c t o r muscle s c a r p i gmen ta t i on d i s - t i n g u i s h e s t h e American o y s t e r f r om s i m i l a r spec ies. I n C. r h i zopho rae and C. g igas t h e musclQ s c a r i s l i g h t l y - pigmented, and i n C. - colnrnercial i s and C. r i v u l a r i s i t 7s unpigmented. A l - - though C. i as has been i n t r o d u c e d t o S a l t P G d eP8 i n l u c H i l l , Maine, We l l - f l e e t Harbor, Massachusetts, and M o b i l e Bay, Alabama, t h e o n l y s i g n i f - i c a n t l y numerous sympat r i c ~ r a s s o s t r e a spec ies i s C. r h i z o horae, which + occurs a l ong t F e sou t eas te rn and g u l f coasts . The s h e l l o f C. r h i z o horae i s l e s s p l i c a t e d t han t h t k i n - i ca . Crassos t rea spec ies at% d i s t i n - - guishab le f r o m Ost rea spec ies by t h e Dresence o f a ~ r o m v a l chamber. which ; s we1 1 d e v e l opedv i n C. v i r g i n i ca. Crassos t rea a r e ov iparous , re1 eas i ng gametes i n t o t h e water , whereas Os t rea i ncuba te f e r t i l i z e d eaas i n t h e man t l e c a v i t y . Advanced ~ G s s o s t r e a 1 a rvae a r e d i s t i n a u i s h e d f r om l a r v a e o f o t h e r b i v a l ves b i l eng th -w i d t h measurements, and an asymmetr ic umbo. The d e n t i t i o n

on t h e h i n g e d i s t i n g u i s h e s l a r v a l C. - v i r g i n i c a f r o m o t h e r Crassost rea.

REASON FOR INCLUSION I N SERIES

American o y s t e r s suppo r t an im- p o r t a n t commercial f i s h e r y f rom t h e G u l f o f Mexico t o t h e G u l f o f St. Law- rence, and a r e an impo r t an t m a r i c u l - t u r e spec ies. More U.S. p l a n t s produce o y s t e r p r o d u c t s t h a n any o t h e r s i n g l e f i s h e r y p roduc t , and over 10,000 peo- p l e a r e employed i n t h e o y s t e r i ndus - t ry. Oys te rs a r e va lued as a l u x u r y f ood i tem. They a r e t h e keys tone spe- c i e s o f a r e e f b i ocoenos i s t h a t i n - c l udes seve ra l hundred spec ies (We1 1 s 1961). Because o y s t e r s occu r i n es tua - r i n e a r e a s , t h e y a r e v u l n e r a b l e t o d i s t u r b a n c e by development p r o j e c t s .

L IFE HISTORY

Spawning

Gametogenesis and spawning a r e s t i m u l a t e d by tempera tu re (Hopkins e t a1 . 1954; Kaufman 1978; Andrews 1979). The tempera tu res a t wh ich spawning occurs d i f f e r among popu la t i ons . Stau- be r (1950) recogn ized t h r e e phys i 01 og- i c a l races, two f r om t h e eas t coas t and one f r o m t h e g u l f c o a s t , w h i c h spawn a t 16.4"C, 20.0°C, and 25.0°C, r e s p e c t i v e l y . Evidence f o r p h y s i o l o g - i c a l races was g i ven by Loosano f f (1969), who found t h a t gametes of 60% of t h e o y s t e r s f r om Long I s l a n d Sound p o p u l a t i o n s r i pened a t 15°C a f t e r 45 days, whereas o n l y 20% o f t h e o y s t e r s f r om a New Jersey p o p u l a t i o n had r i p e gametes a f t e r 72 days a t t h e same tem- pe ra tu re . A t 18°C none o f t h e o y s t e r s f r o m sou th o f New Jersey matured, even a f t e r 3 years . The t i m e r e q u i r e d f o r gonad m a t u r a t i o n (D) i n Long I s l a n d Sound o y s t e r s i s i n v e r s e l y p r o p o r t i on- a1 t o tempera tu re (T ) :

Spawni ng may depend secondar i l y on t i d a l c y c l e ; sun1 i gh t warmed wate r d u r i n g low t i d e and s t i m u l a t e d spawn- i ng ( D r i nnan and S t a l l w o r t h y 1979).

Spawning i s i n i t i a t e d by one o r more males, which re l ease t h e i r sperm and a pheromone i n t o t h e water . The fema les spawn when sperm e n t e r t h e wate r t r a n s p o r t system (Andrews 1979), o r when pheromone s t i m u l a t e s females t o r e l e a s e t h e i r eggs i n a mass spawn- i n g (Bahr and L a n i e r 1981). Females produce 23.2 t o 85.8 m i l l i o n eggs p e r spawning, w i t h t h e number o f eggs p r o p o r t i o n a l t o t h e s i z e o f t h e i n d i - v i d u a l (Davis and Chanley 1955). Fe- c u n d i t i e s o f 15 m i l l i o n t o 115 m i l l i o n were c i t e d by Yonge (1960). Females may spawn seve ra l t i m e s i n one season, and t h e number o f eggs produced i s n o t p r o p o r t i o n a l t o t h e spawning i n t e r v a l . As spawning i n t e r v a l inc reases , ob- v i o u s l y t h e number o f eggs p e r season decreases (Davis and Chanl ey 1955). The spawning season i s l o n g e r i n warm- e r c l i m a t e s : f rom A p r i l t o October i n t h e G u l f o f Mexico (Hayes and Menzel 1981 ) ; b u t f r o m J u l y t o Augus t i n Ma1 peque Bay, P r i n c e Edward I s 1 and (Kennedy and B a t t l e 1963); and o n l y i n Ju l y a t B ide fo rd R i v e r Estuary, P r i n c e Edward I s 1 and, Canada ( D r i nnan and S t a l l w o r t h y 1979). The egg s tage ends a t 6 h r a f t e r f e r t i l i z a t i o n a t 24OC (Loosanof f 1964).

Larvae

Oys te r 1 arvae a r e merop lank ton ic , remain ing i n t h e wate r column f o r 2 t o 3 weeks f o l l o w i n g f e r t i l i z a t i o n (Bahr and L a n i e r 1981). Du r i ng t h i s p e r i o d t h e l a r v a e pass th rough seve ra l s tages o f development ( C a r r i k e r and Palmer 1979). A f t e r t h e b l a s t u l a (3.2 h r ) , g a s t r u l a (4.5 h r ) , and t rochophore (10 h r ) s tages ( P a r r i s h 1969), t h e l a r v a e sec re te a s t r a i g h t - h i n g e s h e l l and d e v e l o p a r i n g o f l o c o m o t o r y c i 1 i a c a l l e d t h e velum. The swimming t rochophore s tage i s reached i n 6-8 h r (Andrews 1979). Th i s p r o d i ssoconch I o r s t r a i g h t - h i n g e l a r v a i s about 75 pm i n d iameter . T h i s s tage i s f o l l o w e d by

prodissoconch 11, which i s cha rac te r - i z e d by p ronounced umbones. These l a r v a e a r e v igorous swimmers w i t h a p a i r o f pigmented eyes and an e l onga te f o o t w i t h a l a r g e byssa l g land (An- drews 1979). These l a r v a e a r e 0.30 mm i n d iameter (Gal t s o f f 1964).

C a r r i k e r (1951) found t h a t young- e r l a r v a e s t a y i n t h e w a t e r co lumn about 1.0 m below t h e sur face. O lder l a r v a e remain near t h e bo t tom i n t h e h a l o c l i n e o f e s t u a r i e s d u r i n g f l o o d t i d e and r i s e nearer t h e sur face du r - i n g t h e ebb t i d e , a l t h o u g h Andrews (1979) ques t ioned t h i s f i n d i n g . Haskin (1964) demonstrated t h a t g r a d u a l l y r i s i n g s a l i n i t i e s s t i m u l a t e o l d e r l a r - vae t o swim and f a l l i n g s a l i n i t i e s cause them t o s i nk . Hidu and Haskin (1978) observed s p i r a l swimming d u r i n g cons tan t s a l i n i t y , and 1 i near swimming d u r i n g g r a d u a l l y i n c r e a s i n g s a l i n i t y ; swimming v e l o c i t y inc reased by a f a c - t o r o f t h r e e a t s a l i n i t y near 100% seawater. Upward swimming i s a t n e a r l y 1 cmlsec (Andrews 1979). These behav io ra l t r a i t s perhaps r e s u l t i n s e l e c t i v e t i d a l t r a n s p o r t and a1 low l a r v a e t o avo id be ing f l u s h e d f r o m t h e es tuary . Larvae may even be t r a n s p o r t - ed up an es tua ry ( S e l i g e r e t a1 . 1982).

Juveni l e s

The l a r v a e a t 2 t o 3 weeks a f t e r spawning seek a s o l i d su r f ace and com- mence a p e r i o d o f c raw l i n g i n a c i r c u - l a r area, presumably seek ing a p l ace f o r a t tachment (Andrews 1979). A f t e r a t tachment w i t h a d r o p l e t of l i q u i d cement exuded f r om a po re i n t h e foo t , t hey l o s e t h e velum and f o o t and a re now c a l l e d spat . S h e l l s a r e p r e f e r r e d as attachment o r s e t t i n g s i t e s , b u t s tones and o t h e r sur faces may be used. Spat t h a t s e t d u r i n g t h e f i r s t 3 days a f t e r metamorphosis may grow f a s t e r t h a n t hose s e t t i n g l a t e r (Losee 1979). Metamorphosis may be delayed i f s u i t - a b l e s u b s t r a t e i s n o t p resen t (Newkirk e t a l . 1977).

Several f a c t o r s i n f 1 uence t h e s e t t i n g behavior o f la rvae. Hidu and Haskin (1971) suggested t h a t r i s i n g temperature over t i d a l f l a t s d u r i n g t h e f l o o d t i d e s s t imu la tes s e t t i n g . I n t h e l abo ra to ry , r i s i n g temperature t r i g g e r e d s e t t i n g (Lu tz e t a l . 1970). Swimming 1 arvae have p o s i t i v e photo- t a x i s , which becomes nega t i ve w i t h increased temperature (Bahr and Lan ie r 1981) . More o y s t e r s s e t t l e d i n t h e s u b t i d a l zone than elsewhere i n Delaware Bay (Hidu 1978). S e t t i n g was grea ter on s h e l l s a t 2 m depth t han on s h e l l s a t 1.2 m o r 0.3 m (Dr innan and S t a l l sworthy 1979). However, Andrews (1979) observed more s e t t i n g o f f t h e bottom, and a t t r i b u t e d t h e oppos i t e r e s u l t s t o s i l t a t i o n i n sha l lower water.

Oys ter l a r v a e s e t i n es tab l i shed o y s t e r beds. C r i sp (1967) p o s t u l a t e d t h a t l a r v a e a re a t t r a c t e d t o t h e pro- te inaceous su r face o f t h e per ios t racum o f a d u l t s h e l l s and observed t h a t l a r - vae do no t s e t t l e on s h e l l s t h a t had been t r e a t e d w i t h bleach. Hidu (1969) demonstrated, however, t h a t a water - borne f a c t o r , perhaps a pheromone, i s invo lved; l a r v a e s e t t l e on o y s t e r s h e l l s assoc ia ted w i t h e x i s t i n g oys- t e r s . Currents a l s o i n f l u e n c e s e t t i n g p a t t e r n s . Keck e t a l . ( 1973 ) f o u n d t h a t s e t t i n g i n e s t u a r i e s i s heav ies t on t h e e rod ing banks o f t i d a l creeks.

Adu l t

Because a d u l t s a r e comple te ly s e s s i l e , t h e i r d i s t r i b u t i o n depends on where t h e l a r vae s e t and on subsequent m o r t a l i t y . Oysters t y p i c a l l y occur i n clumps c a l l e d ree fs o r beds, i n which they a re t h e dominant organism. The mass o f s h e l l s o f t e n r e s u l t s i n a l - t e r a t i o n o f c u r r e n t s and increased depos i t i on so t h a t t h e l o c a l env i ron- ment i s modi f ied.

Adu l t s a re d ioecious, b u t o f t e n change gender (Bahr and Lan ie r 1981). The gender and t h e p r o c e s s o f sex i n v e r s i o n a re g e n e t i c a l l y determi ned by perhaps t h r e e l o c i (Haley 1977).

T y p i c a l l y t h e young a d u l t s a re predominate ly ma1 es; subsequent sex i n v e r s i o n w i t h age increases t h e number o f females. Sex r a t i o s i n t h e James R ive r Estuary, V i r g i n i a , change f rom 90% males a t 1 yea r o f age t o 80% females i n o l d e r oys te rs (Andrews 1979).

GROWTH CHARACTERISTICS

Growth i s g rea tes t d u r i n g t h e f i r s t 3 months, and spat reach 15 mm i n 9 months (Bahr 1976). I n t h e i r sec- ond year , j u v e n i l e s t h a t were 11 t o 14 mm on A p r i l 3 were 18 t o 22 mm on May 7, 23 t o 27 mm on June 5, and 26 t o 32 mm on J u l y 2 ( C a r r i k e r e t a l . 1982). Body weight increased f rom 0.23 g t o 4.0 g d u r i n g t h i s 3-month per iod. Monthly s h e l l increment ranged f rom 1 t o 3 mm per month i n South Ca ro l i na (Manzi e t a l . 1977; Manzi and B u r r e l l 1977 ) ; o r 20 mm p e r y e a r i n Ma ine ( P r i c e e t a1 . 1975). Instantaneous monthly growth c o e f f i c i e n t s ranged f rom 0.42 t o 0.84 ( G i l l m o r 1982). The marketable s i z e o f 90 mm i s a t t a i n e d i n 3 t o 5 years.

Growth i s i n f l uenced by tempera- t u r e , s a l i n i t y , i n t e r t i d a l exposure, t u r b i d i t y , and food. Growth i s g rea t - e s t i n August and September a f t e r spawning, when glycogen reserves a re res to red (Loosanof f and Nomejko 1949; P r i c e e t a l . 1975). Growth ceases dur- i ng wi n t e r , except i n F l o r i d a , where growth was cont inuous throughout t h e yea r ( B u t l e r 1952). Growth i s slowed by spawning because energy i s used f o r gamete p roduc t i on i n s t e a d o f p ro- duc t i on o f body biomass. B u t l e r (1953) noted a weight inc rease a f t e r spawning w i t h o u t an inc rease i n length .

F l u c t u a t i n g environments may pro- mote b e t t e r growth. Oysters i n f l u c - t u a t i n g s a l i n i t y grow b e t t e r t han those under constant c o n d i t i o n s (P ie rce and Conover 1954). Oysters exposed d u r i n g t h e t i d a l c y c l e grow about t h e same as those cont inuous ly submerged (Gi l l m o r 1982). Long expos-

ure, however, reduced growth ; those exposed 20% o f t he t ime grow t w i c e as f a s t as those exposed 60% o f t h e t ime. Growth r a t e i s d i r e c t l y r e l a t e d t o phytoplankton dens i ty , and some o f t h e observed e f f e c t s may be due t o changes i n phytoplankton. Manzi e t a1 . (1977) observed t h a t oys ters grow f a s t e r i n s a l t ponds than i n t i d a l creeks, where pr imary p r o d u c t i v i t y i s lower. Crowd- i n g may prevent spawning and thus i n - d i r e c t l y may lead t o increased growth ( B u t l e r 1953).

Oysters over 200 mm long are no t uncommon. A Wal ford p l o t o f i n t e r t i d a l oys te rs p r e d i c t s t h a t oys te rs would cease growing a t 140-mm leng th (Dame 1971).

COMMERCIAL HARVEST

The Amer ican o y s t e r had t r a d i - t i o n a l l y supported a s i g n i f i c a n t i n - dus t ry a long t h e e n t i r e eastern sea- board. Today, t h e r e are on l y s i x com- merc ia l areas i n t h e North A t l a n t i c r e g i o n (F igure 2). Domestic 1 andi ngs have decreased from about 100 mi 11 i o n l b d u r i n g t h e 1920's t o 50 m i l l i o n 1b du r ing t h e 19601s, and have not recov- ered t o t h e o r i g i n a l l e v e l s (Table 1 ) (Matthiessen 1969). A1 though harvests i n t h e Gul f o f Mexico and South At lan- t i c have remained s t a b l e f o r t h e past 30 years, harves ts i n t h e m i d - A t l a n t i c and Chesapeake Bay have decl ined. I n Long I s l a n d Sound, p e r s i s t e n t se t f a i l u r e has been respons ib le f o r de- c l i n i ng stocks. A1 though oys te rs spawn a t t h e summer temperatures o f t h e sound (20" t o 21°C), s e t t i n g must occur i n warmer es tuar ies . Because o f shore1 i n e development, t h e amount of s e t t i n g area has decl i ned (Matthiessen 1969). Heavy m o r t a l i t i e s due t o t h e predatory ; tar f ish As te r i as f o r b e s i and t h e gastropod Urosal p i nx c i nerea i n sa l twater , and t h e predatory f l a t - worm St lochus e l l i p t i c u s i n b rack i sh water&l so con t r i bu ted t o de- c l i n i n g stocks (Matthiessen 1979).

Oysters are harvested i n a v a r i e t y o f ways, i n c l u d i n g handpick ing o f clumps from ree fs (Bahr and Lan ier 1981), hand and patent tonging, and dragging f rom s a i 1 powered c r a f t i n t h e Chesapeake Bay, and dredging f rom powercraft i n Long I s l a n d Sound and ( K o r r i nga 1976).

The American o y s t e r i s a l s o one o f t h e p redominan t s p e c i e s used i n mar i cu l t u re , i n c l u d i n g i n t h e North A t l a n t i c region. I n 1980 t h e y i e l d o f c u l t u r e d oys ters was 23,705,000 1b valued a t $37,085,000. Th is repre- s e n t s 55% o f t h e t o t a l h a r v e s t o f 42,439,000 l b . The equivalences be- tween d i f f e r e n t values repor ted f o r harves t are: 1 bu = 34 1 = 32 kg t o t a l weight = 7.8 p i n t s = 3.4-kg meat weight (Pruder 1975).

The marke t q u a l i t y v a r i e s w i t h t h e season. The y i e l d o f meats i s low- e s t i n t h e summer months and peaks i n March (Rockwood and Mazek 1977). Th is corresponds t o a reduced-condi t i on index f o l l owing spawning (Hopki ns e t a1 . 1954; Lawrence and Sco t t 1982).

Popu la t ion Dynamics

The enormous numbers o f eggs and l a r v a e produced by American oys te rs l a r g e l y p e r i s h before s e t t i n g . Fol low- i n g spawning, oys te r l a r v a e are common i n t h e p lankton, w i t h numbers reaching 5,000 t o 10,00O/kl i n Canadian waters ( D r i nnan and S ta l lwo r thy 1979) and 2,000 t o 5,50O/kl i n V i r g i n i a (Andrews 1979; S e l i g e r e t a l . 1982) , w i t h a peak i n abundance a f t e r h i g h t i d e (Andrews 1979). The d a i l y m o r t a l i t y o f l a r vae i s 10% (Drinnan and S ta l lwo r thy 1979). Newly se t spat had 79% t o 99% m o r t a l i t y i n 1 month i n Massachusetts (Krantz and Chamber1 i n 1978). Spat m o r t a l i t y o f 50% t o 70% i n Delaware Bay was reduced t o 30% t o 40% i f spat were p ro tec ted from predators (Tweed 1973). Spat s u r v i v a l was l e s s i n dense se ts than i n sparse se ts i n Chesapeake Bay (Webster and Shaw 1968). Annual changes i n popu la t i on dens i t y i n Long

I

I I

MILES 0 50 100

0 50 100

KILOMETERS

Commercial oyster areas

A TL A N TIC OCEAN

Figure 2 . Recent commercial American o y s t e r a r e a s i n t h e North A t l a n t i c Region. Commercial ha rves t i s now p roh ib i t ed i n Great Bay and i s low i n P l ea san t Bay (Ralph Andrews, U.S. Fish and W i l d l i f e S e r v i c e , Newton Corner , Massachuset ts) .

T a b l e 1. O y s t e r h a r v e s t s ( t h o u s a n d s o f pounds meat w e i g h t ) by geograph ica l r e g i o n f o r t h e yea rs 1950-1980 ( f r o m va r i ous i s sues o f Cu r ren t F i s h e r i e s S t a t i s t i c s , N a t i o n a l Oceanic and Atmospheric A d m i n i s t r a t i o n ) .

South G u l f o f Year New ~ n g l a n d ~ id-Atlantic Chesapeake A t l a n t i c Mexico

a I n c l u d e s Connec t i cu t and Rhode I s 1 and f rom t h e Mid-At1 a n t i c Region. b N/A = Data n o t a v a i l a b l e .

I s l a n d Sound (MacKenzie 1981) suggest 94% i n an e s t u a r y (Manzi and B u r r e l l s u r v i v a l r a t e s : spa t occur a t dens i - 1977). S u r v i v a l was 100% i n areas t i e s o f 200 t o 10,000/m2; 1- t o 2-year p r o t e c t e d from wave a c t i o n i n Nor th o l d s a t 300/m2; and 3- t o 4-year-o lds Ca ro l i na , and 50% p e r month i f exposed a t 75/m2. A d u l t s u r v i v a l i n South t o waves (Or tega 1981). C a r o l i n a was 85% i n a s a l t pond and

ECOLOGICAL ROLE

Larvae feed on p lank ton . G u i l l a r d (1957) observed t h a t sma l l , naked f 1 age1 1 a t e s (ch rysophy tes ) a r e t h e p r e f e r r e d food f o r l a r vae . Dav is and C a l a b r e s e ( 1 9 6 4 ) f ound t h a t a t l o w tempera tu res l a r v a l growth i s b e s t w i t h a d i e t o f naked f l a g e l l a t e s : whereas a t tempera tu res above 27°C naked a l gae do n o t s u r v i v e and c h l o r o - phy tes a r e a b e t t e r food source. La r - vae i n t u r n se r ve as food f o r a w ide v a r i e t y of f i 1 t e r feeders (Andrews 1979).

The a d u l t s a r e impo r t an t f i 1 t e r feeders i n e s t u a r i ne ecosystems and f eed on naked f l a g e l l a t e s i n t h e 3- t o 4-pm s i z e range (Haven and Mora les - A lamo 1 9 7 0 ) . F o r each gram o f d r y we igh t o f t i s s u e , an o y s t e r f i l t e r s 1.5 l / h r , w i t h a maximum o f 1.9 l / h r (Palmer 1980). The f i l t e r a t i o n r a t e i s independent of t h e a l g a l f ood concen- t r a t i o n i n t h e seawater.

Oys te r s a r e t h e keys tone spec i es o f a d i v e r s e community i n t h e e s t u - a r i n e ecosystem. Bahr and L a n i e r (1981) r e p o r t e d t h e occur rence o f 42 macrofaunal spec ies o r groups, and Wel l s (1961) l i s t e d 303 spec i es assoc i a t ed w i t h t h e o y s t e r community. Because o f t h e i r abundance, o y s t e r s a r e r e s p o n s i b l e f o r 87.5% o f t h e r e s - p i r a t i o n o f an o y s t e r r e e f (Bahr and L a n i e r 1981).

Oys te rs a r e sub jec ted t o a v a r i - e t y o f d i seases and p a r a s i t e s and sup- p o r t seve ra l p r e d a t o r p o p u l a t i o n s (Gal t s o f f 1964). B a c t e r i a1 d i seases i n c l u d e V i b r i o and Pseudomonas spe- c i e s . The fungus Dermocyst id ium marinum i n f e c t s o y s t e r s i n t h e sou th - e r n range f r o m Delaware t o Mexico. The ha01 o s o o r i d i an o ro tozoan M i n c h i n i a nelson; i s r e s p o n s i b l e f o r t h e d i sease M S X u l t i n u c l e a t e sphe ro i d unknown), and M i n c h i n i a c o s t a l i s f o r SSO (sea- s i d e organism-hinia n e l s o n i , found f rom N o r t h C a r o l i n a t o Massachu- s e t t s ( K r a n t z e t a l . 1 9 7 2 ) , c a u s e d e x t e n s i v e o y s t e r m o r t a l i t i e s i n t h e

8

Delaware Bay i n 1957 and i n Chesapeake Bay i n 1960 (Andrews 1968). M i n c h i n i a c o s t a l i s caused e x t e n s i v e m o r t a l i t i e s i n t h e seas i de bays o f t h e Delmarva Pen insu la i n 1960 ( R o s e n f i e l d 1971).

Oys te r p r e d a t o r s i n c l u d e t h e gas t ropod o y s t e r d r i 11 s (Urosa l p i nx c i nerea and Eupl eu ra cauda ta ) , t h e whel (Busycon c a n a l i cul), t h e starf ish-r ias f o r b e s i ) , and t h e c rabs (Cancer i r r o r a t u s , C a l l i nec tes sa idus , and Carc inus maenus) (Gal t s o f f * A1 1 o y s t e r s a r e s u s c e p t i b l e t o p r e d a t i o n by o y s t e r d r i l l s , wh ich bo re t h rough t h e s h e l l s w i t h a comb ina t ion o f chemica l d i s s o l u t i o n o f t h e s h e l l and d r i 11 i ng; b u t o n l y sma l l e r o y s t e r s a r e s u s c e p t i b l e t o p r e d a t i o n by c rabs and s t a r f i s h . Widespread i n f e s t a t i o n a l s o o c c u r s f r o m t h e b o r i n g sponge C l iona, wh ich l owe rs qua1 i t y . Oys te r =may be smothered by e x c r e t a o f worms o f t h e genus Polydora. Juven i 1 es a r e p reyed upon by t h e f l a t w o r m S t y l o - chus e l 1 i p t i c u s (MacKenzie 1970).

M a j o r compe t i t o r s o f t h e o y s t e r i n c l u d e t h e s l i p p e r l i m p e t s sp. ) and t h e j i n g l e sp.) as w e l l as ba rnac l es and o t h e r o v s t e r s t h a t s e t on a d u l t s h e l l s (Mac- ~ i n z i e 1970). The mussel ( ~ r a c h i o d o n - t e s e x u s t u s ) may a l s o compete w i t h m e m e g a 1981).

ENVIRONMENTAL REQUIREMENTS

The American o y s t e r t y p i c a l l y 1 i ves i n s h a l l ow, we1 1 -mi xed es tu - a r i e s , lagoons, and ocean ic bays t h a t f l u c t u a t e w i d e l y f rom h o t t o c o l d tem- pe ra tu res , low t o h i g h s a l i n i t i e s , and c l e a r t o muddy wa te r s (Andrews 1979). Because t h e y l i v e i n such an ex t r eme l y v a r i e d h a b i t a t , exac t env i ronmental r e q u i rements a1 one o r i n comb ina t ion a r e d i f f i c u l t t o de f i ne .

Temperature

L a r v a e do n o t t o l e r a t e as w ide a range o f tempera tu res as a d u l t s . Water t e m p e r a t u r e s o f 30" t o 34°C i m p a i r

growth, and even a b r i e f exposure f o r 10 min a t 40°C r e t a r d s growth i n Cheasepeake Bay (Hidu e t a1 . 1974). The temperatures c i t e d f o r f a s t e s t growth and h i g h e s t s u r v i v a l , 27.5O t o 32.5OCY i n Long I s l a n d Sound (Davis and Calabrese 1964), seem a b i t h igh .

A d u l t s t o l e r a t e a water tempera- t u r e range f rom -1.7OC i n New England t o 36OC i n t h e G u l f o f Mexico. Oysters may be exposed a t low t i d e t o temper- a tu res below f r e e z i n g o r above 4g°C ( G a l t s o f f 1964). High temperatures i nc rease t h e mor ta l i t y r a t e ; tempera- t u r e s above 35OC f o r t h e whole t i d a l c y c l e caused d e a t h o f some o y s t e r s (Tinsman and Maurer 1974). The c r i t i - c a l thermal maxima f o r t h e American o y s t e r i s 48.5OC (Henderson 1929). Oysters t o 1 e r a t e f r e e z i n g o f t h e i r t i s s u e s , and r e v i v e a f t e r thawing (Loosanof f 1965a).

Optimum temperatures f o r a d u l t American o y s t e r s a r e 20' t o 30°C. Op- timum temperatures f o r pumping were 20' t o 25OC ( C o l l i e r 1951) . Growth ceased below about 8OC ( P r i c e e t a l . 1975). Oysters a t 2' t o 7OC remained i n a c t i v e . Exposure t o warm tempera- t u r e s ou t o f season s t imu l a ted growth i f food was a v a i l a b l e (Ruddy e t a l . 1975). Growth i s p o s s i b l e between 6' and 32OC w i t h t h e optimum a t 25' t o 26OC ( G a l t s o f f 1964). Exposure t o 35OC water acce le ra ted gametogenesis and spawning, b u t subsequent spawning was prevented (Qu ick 1971).

D i f f e r e n c e s i n thermal r equ i r e - ments o f o y s t e r s f rom d i f f e r e n t areas have l e d t o t h e p o s t u l a t i o n o f d i f f e r - en t races, each w i t h d i f f e r e n t temper- a t u r e requ i rements (Ahmed 1975). Spawning temperatures f o r t h r e e d i s - t i n c t races were repo r ted by Stauber (1950) t o be 16.4OC f o r t h e n o r t h e r n r a c e (New E n g l a n d ) , 20.0°C f o r t h e m i d - A t l a n t i c race, and 25.0°C f o r t h e Gu l f o f Mexico race. A d d i t i o n a l e v i - dence f o r t h e ex i s tence o f phys io l og - i c a l races was repo r ted by Menzel (1955), who found t h a t c i 1 i a r y a c t i v- i t y con t inued a t O°C i n n o r t h e r n

oys te rs bu t ceased a t 6OC i n southern oys te rs . Andrews (1979) be1 i eves t h e r e a r e o t h e r races as w e l l . Genet ic s tud- i e s d i d n o t c l o s e l y suppor t t h e e x i s t - ence o f p h y s i o l o g i c a l races. Buroker e t a l . (1979) found t h a t a l l oys te r s s t u d i e d were i d e n t i c a l , except oys te rs f rom Nova S c o t i a and F l o r i d a . These popu la t i ons were 82% s i m i l a r , about t h e l e v e l o f s i m i l a r i t y be tween C. v i r g i n i c a and C. can success fu l 1 7 - - L a n i e r 1981). Oysters i n ~ a ~ u n a Madre, Texas, however, a r e g e n e t i c a l l y d i s - t i n c t f rom f o u r o t h e r g u l f popu la t i ons (Groue and L e s t e r 1982). Measurement o f isozymes i n t h e gene t i c s tud ies , however, may n o t i n d i c a t e these races.

S a l i n i t i e s

S a l i n i t i e s above 7.5 p p t a re re - q u i r e d f o r spawning (Loosanof f 1948). Larvae t o l e r a t e s a l i n i t i e s o f 3.1 t o 30.6 p p t ( C a r r i k e r 1951 ) , b u t grow f a s t e s t and s u r v i v e bes t a t s a l i n i t i e s above 12.5 pp t (Davis and Calabrese 1964 ) . Most l a r v a e i n a New J e r s e y es tua ry were i n t h e h a l o c l i n e a t s a l i n i t i e s above 5 pp t ( C a r r i k e r 1951). Optimum s a l i n i t i e s f o r t h e g r o w t h o f s p a t we re 15 t o 22 p p t (Chanley 1957).

A d u l t oys te r s t o l e r a t e a s a l i n i t y range o f 5 t o 30 pp t , o u t s i d e o f which t hey d i s c o n t i n u e f eed ing and reproduc- i ng . The optimum s a l i n i t y range i s 10 t o 28 p p t (Loosanof f 1965a). Loosanof f (1965b) found t h a t many oys te rs su r - v i v e 3 p p t f o r 30 days. Large mor ta l - i t i e s , however, have been assoc ia ted w i t h pro longed s p r i n g f l o o d s i n t h e James R i ve r , V i r g i n i a (Andrews e t a l . 1 9 5 9 ) ; i n M o b i l e Bay, Alabama (May 1972); and i n t h e Santee R iver , South C a r o l i n a ( B u r r e l l 1977). S a l i n i t i e s d u r i n g t h e s e f r e s h e t s we re be low 2 pp t . Oysters i n Lou i s i ana d ied a f t e r 14 days a t 6 pp t (Anderson and Anderson 1975).

Low s a l i n i t y i n h i b i t s gonadal m a t u r a t i o n i n o y s t e r s i n Chesapeake Bay ( B u t l e r 1949) and Long I s l a n d

Sound (Loosanof f 1953). Reproduct ive f a i l u r e may be a d i r e c t e f f e c t of sa- l i n i t y o r m igh t be caused by inade- quate f eed ing a t low s a l i n i t y . Lowered s a l i n i t y may b e n e f i t o y s t e r popula- t i o n s by k i l l i n g p redators . Oyster d r i l l s and s t a r f i s h cannot t o l e r a t e b r a c k i s h water (Loosanof f 1965a).

Hab i t a t

Oysters can grow e q u a l l y w e l l on r o c k y b o t t o m s o r on mud c a p a b l e o f suppo r t i ng t h e i r weight . S o f t muddy subs t ra tes may be improved by adding clam o r o y s t e r s h e l l s . Oysters f rom muddy subs t ra tes a r e more s l ende r t han those f rom ha rd subs t ra tes (Ga l t so f f 1964). Hidu (1978) found t h a t o y s t e r s p r e f e r t o s e t on t h e b o t t o m r a t h e r than on panels suspended i n t h e water column, and a r e g e n e r a l l y found sub- t i d a l l y i n Delaware Bay. The p r e f e r r e d h a b i t a t s i n sha l low e s t u a r i n e waters i n c l u d e f l a t s and o f f s h o r e bars (Hidu 1968) and o y s t e r r e e f s (Bahr and Lan- i e r 1981). Maximum s e t t i n g occurs on h o r i z o n t a l sur faces (Cl ime 1976).

Cu r ren t s a re impor tan t t o Ameri- can oys te rs . The volume o f water i m - med ia te l y above an o y s t e r bed must be renewed 72 t imes every 24 h r f o r maxi- mum feeding; t h e r e f o r e , oys te rs r e - qu i r e a moderate c u r r e n t (Gal t s o f f 1964). T i d a l f l ows o f 156 t o 260 cm/sec o r h i g h e r a r e needed f o r o p t i - mum growth (Veal e t a l . 1972). Turbu- l e n t cu r ren t s , however, can damage s h e l l s f rom t r a n s p o r t e d sand and peb- b l e s ( G a l t s o f f 1964). A l though a v e l o c i t y o f 150 cm/sec caused un- a t tached o y s t e r s t o tumble a long t h e b o t t o m (MacKenz ie 1981 ) . They a r e found i n g rea tes t abundance i n areas of scour where c u r r e n t keeps t h e beds f r e e o f sediment (Keck e t a l . 1973). Cur ren ts a r e a l s o necessary f o r removal o f s i l t and feces.

D i s t r i b u t i o n i s s t r o n g l y c o r r e - l a t e d w i t h mean low t i d e (MLT) e l e v a t i o n i n Great Bay, New Hampshire ,(Hardwi ck-Wi tman and Mat th iesson 1983). There were 5.6/m2 a t 0 m MLT

2 e l e v a t i o n , 2.0/m2 a t 0.5 m, 0.4/m a t 1 m, and none a t 1.5 m.

Other Envi ronmental Fac to rs

Hour ly oxygen consumption i s 39 ml /kg f o r a whole an ima l o r 303 ml /kg o f wet t i s s u e (Hammen 1969). Oxygen consumption i ncreases w i t h i n c r e a s i n g temperature; Q10 va lues ( t h e f a c t o r by which a r e a c t i o n v e l o c i t y i s inc reased by a r i s e i n temperature o f 10°C) r e - p o r t e d by Bass (1977) range f rom 1.2 t o 2.3 f o r g i l l and 2.7 t o 4.2 f o r mant le t i s s u e . There i s a s t r o n g i n - t e r a c t i o n between temperature and s a l i n i t y ; oxygen consumption inc reases much more a t h i g h temperatures i f t h e s a l i n i t y i s ;ewer' (F igu re 3). Oysters a r e f a c u l t a t i v e anaerobes and a r e ab le t o s u r v i v e d a i l y exposure. They can a l s o s u r v i v e a n a e r o b i c a l l y f o r 3 days f o l l o w i n g spawning (Gal t s o f f 1964). Oxygen consumption i s ze ro w i t h t h e va l ves c l osed (Hammen 1969).

Oys te rs a re a b l e t o t o l e r a t e t u r b i d w a t e r , b u t pumping r a t e de- creases w i t h i n c r e a s i n g t u r b i d i t y . Pumping r a t e can be reduced 70%-85% over t h e range 0 t o 1 g / l , depending on t h e na tu re o f t h e suspended sed i - ment (Loosanof f and Tommers 1948). I n n a t u r a l environments, however, oys te rs grow b e t t e r i n t h e more t u r b i d zones i n o y s t e r beds t h a n i n l e s s t u r b i d areas (Rhoades 1973).

F i g u r e 3. Oxygen consumption i n Ameri- can o y s t e r as a f u n c t i o n o f s a l i n i t y and temperature (Shumway 1982).

LITERATURE CITED

Ahmed, M. 1975. S p e c i a t i o n i n l i v i n g o y s t e r s . Adv. Mar. B i o l . 13: 357-397.

Anderson, R.D., and J.W. Anderson. 1975. E f f e c t s o f s a l i n i t y and s e l e c t e d pe t r o l eum hydrocarbons on osmo t i c and c h l o r i d e r e g u l a - t i o n o f t h e American o y s t e r Cras- s o s t r e a v i r g i n i c a . P h y s i o l . Zool. --20-430.

Andrews, J .D. 1968. Oys te r m o r t a l i ty s t u d i e s i n V i r g i n i a : V I I . Review o f e p i z o o t i 01 ogy and o r i g i n o f M i n c h i n i a n e l s o n i . Proc. N a t l . Shel l f i s h . Assoc. 58:23-36.

Andrews, J.D. 1979. Pel ecypoda: Os t r e i dae . Pages 291-341 i n A.C. Giese and J.S. P e a r s e y eds. Rep roduc t i on o f mar ine i n v e r t e - b ra tes . Vol . V. Mol l u s c s : Pe lecy - pods and l e s s e r c lasses . Academic Press, New York.

Andrews, J.D., D. Haven, and D.B. Quayle. 1959. Freshwater k i l l o f o y s t e r s (Crassos t rea v i r g i n i c a ) i n James R i ve r , V i r q i n i a , 1958. Proc. N a t l . s h e l l f i s h ' : ASS-oc. 49: 29-49.

Bahr, L.M., Jr. 1976. E n e r g e t i c aspec t s o f t h e i n t e r t i d a l o y s t e r r e e f community a t Sapelo I s l a n d , Georgia. Ecology 57(1):121-131.

Bahr, L.M., and W.P. Lan ie r . 1981. The eco logy o f i n t e r t i d a l o y s t e r r e e f s o f t h e South A t l a n t i c c o a s t : a community p r o f i l e . U.S. F i s h and W i l d l f i e Se rv i ce , O f f i c e

o f B i 01 o g i c a l Serv ices , Washing- t on , D.C. FWS/OBS-81/15.

Bass, E.L. 1977. I n f l u e n c e s o f temper- a t u r e and s a l i n i t y on oxygen con- s u m ~ t i o n o f t i s s u e s i n t h e Amer- ica;) o y s t e r (Crassos t rea v i r g i n - i c a l . Com~. Biochem. Phvsi 01.

Buroker , N.E., W.K. Hershberger, and K.K. Chew. 1979. Popu la t i on ge- e t i c s o f t h e f a m i l y Os t r e i dae 2. I n t r a s p e c i f i c s t u d i e s o f t h e gen- e r a ~ r a s s o s t r e a and Saccostrea. Mar. B i o l . ( B e r l i n ) 54:1/1-184.

B u r r e l l , V.G., J r . 1977. M o r t a l i t i e s o f o y s t e r s and ha rd clams assoc i - a t e d w i t h heavy r u n o f f i n t h e Santee R i v e r system, South Caro- l i n a , i n t h e s p r i n g o f 1975. Proc. N a t l . S h e l l f i s h . Assoc. 67 : 35-43.

B u t l e r , P.A. 1949. Gametogenesis i n t h e o y s t e r u n d e r c o n d i t i o n s o f depressed s a l i n i t y . B i o l . B u l l . (Woods Ho le ) 96(3 ) : 263-269.

B u t l e r , P.A. 1952. Seasonal growth o f o y s t e r s (C. v i r g i n i c a ) i n F l o r i - da. P roc .Na t1 . Shel 1 f i s h . Assoc. 43:188-191.

B u t l e r , P.A. 1953. S h e l l growth versus meat y i e l d i n t h e o y s t e r C. v i r - . Proc. N a t l . Shel l f i s h .

44: 157-162.

Cake, E.W. 1983. H a b i t a t s u i t a b i l i t y i n d e x models: G u l f o f Mexico American oys te r . U.S. Dept. I n t .

F ish Wi ld l . Serv. FWS/OBS-82/10. 57. 37 pp.

Ca r r i ker , M.R. 1951. Eco log i ca l obser- v a t i o n s on t h e d i s t r i b u t i o n o f oys te r l a r vae i n New Jersey es tu- a r i es. Ecol . Monogr. 21 ( 1 ) : 19-38.

Ca r r i ke r , M.R., and R.E. Palmer. 1979. U l t r a s t r u c t u r a l morphogenesi s of ~ r o d i ssoconch and e a r l Y d i sso- conch valves o f t h e oyster (Cras- sos t rea v i r i n i c a ) . Proc. Na t l . Shel lfish*69: 103-128.

Car r i ke r , M.R., C.P. Swann, and J.W. Ewart. 1982. An exp lo ra to ry study w i t h t h e pro ton microprobe of t h e ontogenet ic d i s t r i b u t i o n of 16 elements i n t h e s h e l l o f l i v i n a oys ters (Crassostrea v i rgi nica) : Mar. B i o l . (Ber l .) 69: 235-246.

and s a l i n i t y on development o f eggs and growth o f l a r v a e of M. mercenaria and C. v i r i n i c a . U.T. F i s h Wi ld l . S~rv* B u l l . 63(3):643-655.

Davis, H.C., and P.E. Chanley. 1955. Spawning and egg p r o d u c t i o n o f o y s t e r s and c lams. B i o l . B u l l . (Woods Hole) 110:117-128.

Drinnan, R.E., and W.B. S t a l lworthy. 1979. Oyster l a r v a l populat ions and assessment o f spat fa1 1, B i d e f o r d R i v e r , P. E. I., 1963 and 1964. Can. F ish. Mar. Serv. Tech. Rep. (797): l-13.

G a l t s o f f . P.S. 1964. The American oys ier Crassost rea v i r g i n i ca (Gmelinl . U.S. F i s h Wi ld l . Serv.

Chanley, P.E. 1957. Su rv i va l of some Gi l lmor , R.B. 1982. Assessment of j u v e n i l e b i v a l v e s i n water of low i n t e r t i d a l growth and capac i ty s a l i n i t y . Proc. Na f l . S h e l l f i s h . adapta t ions i n suspensi on-feedi n Assoc. 48: 52-65. b i va l ves . Mar. B i o l . (Ber l .

68(3) : 277-286. 7

Clime, R.D. 1976. S e t t i n g o r i e n t a t i o n i n t h e oys ters Ostrea e d u l i s L. and Crassostrea ~ c C i 7 5 S i n. +- Groue, K.J., and L.J. Lester . 1982. Master 's Thesis n l v e r s i t y o f A morphological and genet ic Maine a t Orono. 94 pp. ana l ys i s o f geographic v a r i a t i o n

amona oys ters i n t h e Gulf of C o l l i e r , A. 1951. A study o f t h e re - ~ e x i i o . i e l i ger 24(4) : 331-335.

sponse of oys te rs t o temperature and some 1 ong-range eco log i ca l i n t e p r e t a t i o n s . Proc. Na t l . Shel l f i s h . Assoc. 42: 13-38.

Crisp, D.J. 1967. Chemical f ac to rs i nducina se t t lement i n Crassos- t r e a v i r i n i c a ( ~ m e l i n ) . J. ~ n i m . m.&29-335.

Dame, R.F., Jr . 1971. The e c o l o g i c a l energ ies o f growth, r e s p i r a t i o n and a s s i m i l a t i o n i n t h e i n t e r - t i d a l American o y s t e r Crassostrea v i r i n i c a (Gmelin). Ph.D. Thesis. I+-- n i v e r s i t y o f South Carol ina, Columbia. 81 pp.

Davis, H.C., and A. Calabrese. 1964. Combined e f fec t s o f temperature

G u i l l a r d , R.R. 1957. Some f a c t o r s i n t h e use o f nannopl ankton c u l t u r e s as food f o r l a r v a l and j u v e n i l e b iva lves . Proc. Na t l . She l l f i sh . Assoc. 48:134-142.

Haley, L.E. 1977. Sex determinat ion i n t h e Amer ican o y s t e r . J. Hered. 68(2):114-116.

Hammen, C.S. 1969. Metabolism of t h e o y s t e r Crassostrea v i r g i n ica. Am. Zool. 9 w .

Hardwick-Witman, M.N., and G.C. Mat- th iessen. 1983. I n t e r t i d a l macro- a1 gae and i nve r teb ra tes ; seasonal and s p a t i a l abundance pa t te rns a long an es tua r ine gradient .

E s t u a r i n e Coas ta l She1 f S c i . e n t s a l i n i t i e s and temperatures. 16(2):113-129. E s t u a r i e s l ( 4 ) : 252-255.

Haskin, H.H. 1964. The d i s t r i b u t i o n o f o y s t e r l a r vae . Proc. o f a sympo- s ium on exper imenta l mar ine e c o l - ogy. Occas. Pap. 2, Grad. School Oceanogr. Univ. R.I.:76-80.

Haven, D.S., and R. Morales-Alamo. 1970. F i l t r a t i o n o f p a r t i c l e s f r o m suspension by t h e American o y s t e r ' ~ r a s s o s t r e a v i r i n i ca

-I&Fm+ B i o l . ~ u l l . I W o o d s o l e

Hayes, P.F., and R.W. Menzel. 1981. The r e p r o d u c t i v e c y c l e o f e a r l y s e t t i n g Crassos t rea v i r g i n i c a (Gmel in) i n t h e n o r t h e r n G u l f o f Mexico, and i t s i m p l i c a t i o n s f o r p o p u l a t i o n r e c r u i t m e n t . B i o l . B u l l . (Woods Ho le ) 160:80-88.

Henderson, J.T. 1929. L e t h a l tempera- t u r e s o f Lame1 l i b r a n c h i a t a . Con- t r i b . Can. B i o l . 4(25) : 397-411.

Hidu, H. 1968. I nsho re s e t t l e m e n t o f C rassos t r ea v i r g i n i ca i n Delaware bay. Proc. N a t l . S h e l l f i s h . Assoc. 58:4. (Abs t r . )

Hidu, H. 1969. Gregar ious s e t t i n g i n t h e American o y s t e r Crassos t r ea v i r i n i c a Gmelin. Chesapeake Sci . +92.

Hidu, H. 1978. S e t t i n g o f e s t u a r i n e i n v e r t e b r a t e s i n Delaware Bay, New Jersey, r e l a t e d t o i n t e p - t i d a l - s u b t i d a l g rad i en t s . Ifit. Rev. Gesamten Hyd rob io l . 63:637- 662.

Hidu, H., and H.H. Haskin. 1971. S e t t i n g o f t h e A m e r i c a n o y s t e r r e l a t e d t o env i ronmenta l f a c t o r s and 1 a r v a l behav io r . Proc. N a t l . Shel l f i s h . Assoc. 61: 35-50.

Hidu, H., and H.H. Haskin. 1978. Swimming speeds of o y s t e r l a r v a e Crassos t rea v i r g i n i c a i n d i f f e r -

Hidu, H., W.H. Roosenburg, K.G. Dro- beck, A.J. McErlean, and J.A. M i - hu rsky . 1974. Thermal t o l e r a n c e of oys te r 1 a rvae Crassost r ea v i r- g i n i c a Gmel i n , as r e l a t e d t o pow- e r p l a n t ope ra t i on . Proc. Na t l . S h e i l f i s h . ~ s s o c . 64: 102-110.

Hopkins, S.H., J.G. Mackin, and R.W. Menzel . 1954. The annual c y c l e o f r ep roduc t i on , growth, and f a t t e n - i n g i n L o u i s i a n a oys te r s . Proc. N a t l . S h e l l f i s h . Assoc. 44:39-50.

Kaufman, Z.S. 1978. Dependence o f t h e t i m e of gamete m a t u r a t i o n and spawning on t h e env i ronmental tempera tu re i n V i r g i n i a o y s t e r

Keck, R., D. Maurer, and L. Wat l ing. 1973. T i d a l s t ream development and i t s e f f e c t on t h e d i s t r i b u - t i o n o f t h e American oys te r . Hydrobi 01 o g i a 42(4) : 369-379.

Kennedy, A.V., and H.I. B a t t l e . 1963. C y c l i c changes i n t h e gonad o f t h e Amer ican o y s t e r Crassos t rea v i r i n i c a . Can. J. Zool. 42(2) : *

Korr inga , P. 1976. Farming t h e cupped o y s t e r s of t h e genus Crassost rea: A m u l t i d i s c i p l i n a r y t r e a t i s e . E l s e v i e r , Amsterdam. 238 pp.

Krantz , G.E., and J.F. Chamberl in. 1978. B l u e c rab p r e d a t i o n o f c u l t c h l e s s o y s t e r spa t . Proc. N a t l . Shel 1 f i s h . Assoc. 68: 38-41.

Kran tz , G.E., L.R. Buchanan, C.A. F a r l e y , and H.A. Carr. 1972. M i n c h i n i a n e l s o n i i n o y s t e r s from hassachuse t t s waters . Proc. N a t l . Shel l f i s h . Assoc. 62:83-85.

Lawrence, D.R., and G.I. Sco t t . 1982. The d e t e r m i n a t i o n and use o f

c o n d i t i o n index o f oys te rs . Es tua r i es 5(1):23-27.

Loosanoff , V.L. 1948. Gonadal deve l - opment and spawning o f o y s t e r s (C v i r i n i c a ) i n low s a l i n i t i e s . AT; t & 1:705. (Abstr . )

Loosanof f , V.L. 1953. Behavior o f o y s t e r s i n w a t e r o f l o w s a l i n - i t i e s . Proc. Na t l . S h e l l f i s h . Assoc. 43:135-151.

MacKenzie, C.L., J r . 1970. Causes o f o y s t e r spat m o r t a l i t y , c o n d i t i o n s o f o y s t e r s e t t i n g beds, and recommendations f o r o y s t e r bed management. Proc. N a t l . She1 1 - f i s h . Assoc. 60:59-67.

MacKenzie, C.L., J r . 1981. B i o t i c po- t e n t i a l and envi ronmenta l r e s i s t - ance i n t h e American o y s t e r Cras- s o s t r e a v i r i n i c a i n Long Im Sound. Aquacu -%- t u r e 22 (3 ) : 229-268.

Loosanof f , V.L. 1965a. The American o r Manzi , J.J., and V.G. B u r r e l l , J r . e a s t e r n oys te r . U.S. F i s h W i l d l . 1977. A comparison o f growth and Serv. C i r c . 205. 36 pp. s u r v i v a l o f s u b t i d a l _Crassostrea

v i r i n i c a i n South Ca ro l i na s a l t Loosanof f, V.L. 1965b. Gonad develop- impoundments. Proc. Na t l .

ment and d i s c h a r q e o f spawn i n + S h e l l f i s h . Assoc. 67: 120-121.

oys te rs of Long I s l a n d Sound. B i o l . B u l l . (Woods Ho le ) 129(3) : 546-561.

Loosanof f , V.L. 1969. M a t u r a t i o n o f gonads o f oys te rs , Crassostrea v i r g i n i ca, o f d i f f e r e n t geographica l areas sub jec ted t o r e l a t i v e l y low temperatures. V e l i g e r 11(3):153-163.

Loosanof f , V.L., and C.A. Nomejko. 1949. Growth o f oys te rs , C.

d u r i n g d i f f e r e n t m i 0 1 . B u l l . (Woods Ho le ) 97(1):82-94.

Loosanof f , V.L., and F.D. Tommers. 1948. E f f e c t o f suspended s i l t

Manzi, J.J., V.G. B u r r e l l , and W.Z. C a r l s o n . 1977. A compar i son o f arowth and s u r v i v a l o f s u b t i d a l Crassostrea v i r g i n i c a (Gmeli n ) i n South Carol i na s a l t marsh i m - - .

poundments. Aquacu l tu re 12:293- 310.

Mat th iessen, G.C. 1969. A rev iew o f o y s t e r c u l t u r e and t h e o y s t e r i n d u s t r y i n Nor th America. Woods Hole Oceanogr. I n s t . Cont r ib . No. 2528. 52 pp.

May, E.B. 1972. The e f f e c t o f f l o o d - water on oys te rs i n Mob i le Bay. Proc. Na t l . S h e l l f i s h . Assoc. 62:67-71.

and substances On rate of Menzel, R.W. 1955. Some phases o f t h e f eed ing of oys te rs . Science 107: b i o l o g y o f Ostrea e q u e s t r i s and a 69-70. comparison w i t h Crassostrea v i r-

i n i c a (Gmelin). Publ. I n s t . Mar. Losee, E. 1979. R e l a t i o n s h i p between h n i v . Tex. 4:69-153.

l a r v a l and spat growth r a t e s i n t h e o y s t e r ~ r - a s s o s t r e a v i r i n i c a .

1+ Newkirk, G.F., L.E. Haley, D.L. Waugh,

Aquacu l tu re 16(2) .123 - and R. Doyle. 1977. Genet ics o f l a r v a e and s p a t g r o w t h r a t e i n

Lu tz , R.A., H. Hidu, and K.G. Drobeck. t h e o y s t e r Crassostrea v i r i n i c a . 1970. Acute tempera tu re i nc rease Mar. B i o l . 7Be r l . ) 41( as a s t imu lus t o s e t t i n g i n t h e

l*

American o y s t e r Crassost rea *- Ortega, S. 1981. Envi ronmental s t r ess ,

F Proc. Na t l . S h e l l f i s h . competi t i on and domi nance o f ssoc 60: 68-71. Crassostrea v i r g i n i ca near Beau-

f o r t , N o r t h C a r o l i n a USA. Mar. B i o l . (Be r l . ) 62(1):47-56.

Palmer, R.E. 1980. Behav io ra l and r hy thm ic aspects o f f i l t r a t i o n i n t h e bay s c a l 1 op, Argopecten i r r a d i a n s concen t r i cus , and t h e o y s t e r , Crassos t rea v i r i n i c a . J. Exp. Mar. B i o l . Eco1&295.

P a r r i s h , F.K. 1369. E a r l y mo l luscan development. Proceedi ngs of t h e con fe rence on she1 1 f i s h c u l t u r e . Reg iona l Mar i ne Resources Coun- c i l , Hauppange, N.Y.

P i e r ce , M.E., and J.T. Conover. 1954. A s t u d y o f t h e growth o f o y s t e r s under d i f f e r e n t e c o l o g i c a l con- d i t i o n s i n Great Pond. B i o l . B u l l . (Woods Ho le ) 107: 318. (Abs t r . ) .

Rockwood, C.E., and W.F. Mazek. 1977. Seasonal v a r i a t i o n s i n o y s t e r meat y i e l d s i n A ~ a l a c h i c o l a Bav. ~ l o r i d a . B u l l . Mar. Sc i . 27 (2 ) - * 346-347.

Rosenf i e l d, A. 1971. Oys te r d iseases o f No r t h America and some methods f o r t h e i r c o n t r o l . Pages 67-78 i n K.S. P r i c e and D. Maurer, eds. - A r t i f i c i a l p ropaga t i on o f com- m e r c i a l l y v a l u a b l e s h e l l f i s h . Uni v e r s i t y o f Delaware, Newark.

Ruddy, G.M., S.Y. Feng, and G.S. Campbell. 1975. The e f f e c t o f p ro l onged exposure t o e l e v a t e d tempera tu res on t h e b iochemica l c o n s t i t u e n t s , gonadal develop- ment, and s h e l l d e p o s i t i o n o f t h e American oys te r , Crassos t rea v i r g i n i ca. Comp . Biochem. Phys i 01 . 518 ( 2 ) : 157-164.

P r i c e , A.H., C.T. Hess, and C.W. Smith. 1975. Observa t ions o f Sel i g e r , H.H., J.A. Boggs, R.B.

Crassos t rea v i r g i n i c a c u l t u r e d i n R i v k i n , W.H. B igg ley , and K.R.H.

t h e hea ted e f f l u e n t and d i s - Aspden. 1982. The t r a n s p o r t o f

charged r a d i o n u c l i d e s o f a o y s t e r l a r v a e i n an es tuary . Mar.

n u c l e a r Dower r e a c t o r . Proc. B i o l . ( B e r l . ) 71 ( 1 ) : 57-72.

N a t l . ~ h e l ' l f i s h . Assoc. 66: 54-68. Shumway, S.E. 1982. Oxygen consumption

Pruder, G.D. 1975. Eng inee r i ng aspec ts o f b i v a l v e m o l l uscan m a r i c u l t u r e : c u l t u r e system c o n f i g u r a t i o n s . Co l l ege o f . Mar ine S tud ies , U n i v e r s i t y o f Delaware, Newark.

Qu ick , J.A., J r . 1971. P a t h o l o g i c a l and p a r a s i t o l o g i c a l e f f e c t s of e l e v a t e d tempera tu res on t h e oys- t e r Crassos t rea v i r g i n i c a w i t h emphasis on t h e pathogen Lab r i n thomyxa marina. Pages 10 &;

n i c i c k , . , ed. A prelimi- na ry i n v e s t i g a t i o n : t h e e f f e c t o f e l e v a t e d t e m ~ e r a t u r e on t h e Amer- i c a n o y s t e r ~ r a s s o s t r e a v i r i n i c a (Gmel in) . F l a . Dep. F 4 a t F T k G F Pro f . Pap.

Rhoades, D.C. 1973. The i n f l u e n c e o f d e p o s i t - f e e d i n g benthos on wate r t u r b i d i t y and n u t r i e n t r e c y c l i n g . Am. J. Sc i . 273: l -22.

i n oys te r s : an overv iew. Mar. B i o l . Le t . 3: l -23.

S t a u b e r , L.A. 1950. The p r o b l e m o f p h y s i o l o g i c a l spec ies w i t h spe- c i a l re fe rence t o o y s t e r s and o y s t e r d r i 11 s. Ecology 31: 109- 118.

S tenze l , H.B. 1971. Oysters . Pages N953-N1224 i n R.C. Moore, ed. T r e a t i s e on-ver tebrate p a l eon- t o l o g y . P a r t N, Vol. 3. Mo l lusca 6. Geo log i ca l Soc i e t y o f America, Inc., and U n i v e r s i t y o f Kansas. Boul de r , Col o.

Tinsman, J.C., and D.L. Maurer. 1974. E f f e c t s o f a the rma l e f f l u e n t on t h e American oys te r . Pages 223- 236 i n J.W. Gibbons and R.R. S h a r i F , eds. Thermal ecology. Proc. Symp. h e l d a t Augusta, Ga. May 3-5, 1973. N a t l . Tech. I n f .

Serv. Sp r ing f i e ld , Va., ISBN 0-87079-014-X.

Tweed, S.M. 1973. Sett lement and sur- v i v a l o f Crassostrea v i r g i n i c a on Delaware Bay seed o y s t e r beds. Proc. Nat l . She1 l f i s h . Assoc. 64: 8-9.

Veal, C.D., W.H. Brown, and W.J. Demoran. 1972. Developments i n o f f -bo t tom oys te r c u l t u r e i n M iss i ss ipp i . Am. Soc. Agr ic . Eng. Pap. 72-575. 20 pp.

Webster, J.R., and W.N. Shaw. 1968. S e t t i n g and f i r s t season su rv i val o f t h e American oys te r Crassos- t r e a v i r in'l'ca near Oxfor-- . land, U.S. F i sh Wi ld l . Serv. Spec. Sci. Rep. Fish. No. 567. 6 pp.

Wells, H.W. 1961. The fauna o f oys ter beds, w i t h spec ia l reference t o t h e s a l i n i t y fac tor . Ecol. Monogr. 31 : 239-266.

Yonge, C.M. 1960. Oysters. W i l l m e r Bro thers and Haran, Ltd., B i rtenhead, London. 209 pp.

50272 -101

REPORT DOCUMENTATION , LREPoRT 2. , 3. Reclpdent's Accession No

PAGE I FWS/OBS-82/11.23* - , _____ I - -- . A 1 4. T ~ t l e and Subtltle 5. Report Date

Species Profiles: Life Histories and Environmental - - July - - 1984 -- -- .. - -. Requirements of Coastal Fishes and Invertebrates (North 6.

Atlantic) -- American Oyster - ---- - --A- - - -. 7. Author(s) 8 Perform~ng Organ~rat ion Rept No

-- Mark A. Sellers and Jon G. Stanley - -. - --A 9. P e r f o r m ~ n g Organlzatlon N a m e and Address 10 Prolect/Task/Work Unit No

Program in Oceanography Maine Cooperative Fishery Research -. University of Maine at Unit 11 Contract(t) or Grant(G) NO

Orono 313 Murray Hal 1 ( c ) Ira C. Darling Center University of Maine Walpole, ME 04573 Orono, ME 04469 (S1

-- - - - - - - - - .--A - - 12. Sponsor~ng 0rganlza:lon N a m e and Address 13. Type of Report L P e r ~ o d Covered

N8tional Coastal Ecosystems Team U.S. Army Corps of ~n~ineeds Fish and Wild1 ife Service Waterways Experiment Statian , - - -- - - - - - - U.S. Dept. of the Interior P.O. Box 631 I 14. Washington, DC 20240 Vicksburg, MS 39180 I -

15. Supplementary Notes

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

16. Abstract ( L i m ~ t . 200 words)

Species profiles are 1 iterature summaries of the taxonomy, morphol ogy, range, 1 ife history, and environmental requirements of coastal aquatic species. They are designed to assist in environmental impact assessment. The American oyster, Crassostrea vir inica, is an important commercial and mariculture species. Spawning occurs + repeated y during warmer months with millions of eggs released. Embryos and larvae are carried by currents throughout the estuaries and oceanic bays where they occur. The few surviving larvae cement themselves to a solid object, where they remain for the remainder of 1 ife. Unable to move, they must tolerate changes in the environment that range from -1.70 to 490C, 5 to 30 ppt salinity, and clear or muddy water.

t - -- - - - - . . . -- - - - 17. Document Analys~s a Descnptors

Estuaries Oysters Growth Feeding

b. Identifiers/Dpen.Ended Terms

American oyster Crassostrea virginica Salinity requirements Temperature requirements

c ~ I S g X a ~ F I i j & l @ r o u p -

18. Ava(lab8lt:y Statement

Unl imi ted Unclassified 16 20 5 c c - 7 t y Clarq i i h s + S R ? 22 Pr L C

Unclassified r S e ~ ANSI-233 18) OPTIONAL FORM 27? (L-771

; i o v ~ e . , y NTl>?F' '

Ce:-.r,.nant o f Ccmmcrce

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