species profiles: life histories and environmental ... · and invertebrates (mid-atlantic) american...

REFERENCECOPY Do Not Remove from the Library

U. S. Fish and Wildlife Service

Biological Report 82 (I 1.65) 700 Cajun Dome Boulevard TR EL.s~-4 July 1986 La foyette, Louisiana 70506

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

AMERICAN OYSTER

Coastal Ecology Group Fish and Wildlife Service Waterways ~xperiment station U.S. Department of the Interior U.S. Army Corps of Engineers

B i o l o g i c a l Report 82 (11.65) TR EL-82-4 J u l y 1986

Species Pro f i les : L i f e H i s t o r i e s and Envi ronmental Requi rements o f Coastal Fishes and Inver tebra tes (M id -A t l an t i c )

AMERICAN OYSTER

Jon G. Stanley Maine Cooperat i ve F ishery 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

and

Mark A. S e l l ers 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 Center

Walpole, ME 04573

P ro jec t Manager Lar ry Shanks

P ro jec t O f f i cer John Parsons

Nat ional Wetlands Research Center U.S. F i sh and W i l d l i f e Serv ice

1010 Gause Boulevard S l i d e l l , LA 70458

Performed f o r U.S. Army Corps o f Engineers

Coastal Ecology Group Waterways Experiment S t a t i o n

Vicksburg, MS 39180

and

Nat iona l Wetlands Research Center Research and Development F i s h and W i l d l i f e Serv ice

U.S. Department of t h e I n t e r i o r Washington , DC 20240

This se r i es should be referenced as fo l lows:

U.S. F i sh and W i l d l i f e Service. 1983-19-. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requirements o f coas ta l f i s h e s and inver tebra tes . U.S. F i sh Wi ld l . Serv. B i o l . Rep. 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 fo l lows:

Stanley, J.G., and M.A. Se l l e rs . 1986. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requirements o f coas ta l f i s h e s and i nve r teb ra tes (Mid- At lant ic) - -Amer ican oyster . U. S. F i sh Wi ld l . Serv. B i o l . Rep. 82(11.65 ). U.S. Army Corps o f Engineers, TR EL-82-4. 25 pp.

PREFACE

Th is species p r o f i l e i s one o f a se r i es on coasta l aquat ic organisms, p r i n c i p a l l y f i s h , o f spor t , commercial, o r eco log i ca l importance. The p r o f i l e s are designed t o p rov ide coasta l managers, engineers, and b i o l o g i s t s w i t h a b r i e f comprehensive sketch o f t he b i o l o g i c a l c h a r a c t e r i s t i c s and environmental requirements o f t h e species and t o descr ibe how popu la t ions o f t he species may be expected t o r e a c t t o environmental changes caused by coasta l development. Each p r o f i 1 e has sec t ions on taxonomy, 1 i f e h i s to ry , eco log i ca l r o l e , environmental requirements, and economic importance, i f app l icab le . A t h r e e - r i n g b inder i s used f o r t h i s s e r i e s so t h a t new p r o f i l e s can be added as they are prepared. Th is p r o j e c t i s j o i n t l y planned and f inanced by t h e U. S. Army Corps o f Engineers and t h e U.S. F i s h and W i l d l i f e Serv ice.

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 t o one of t h e f o l l owing addresses.

I n fo rma t ion Trans fer Specia l i s t Nat ional Wet1 ands Research Center U.S. F i s h and W i l d l i f e Serv ice NASA-Sl i d e l l Computer Compl ex 1010 Gause Boulevard S l i d e l l , LA 70458

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

CONVERSION TABLE

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

m i l 1 i i n e t e r s (mm) c e n t i m e t e r s ( n) m e t e r s (m) k i 1 ometers ( km)

2 square m e t e r s (m ) 10.76 square k i 1 ometers ( km2) 0.3861 h e c t a r e s ( h a ) 2.471

l i t e r s ( 1 ) c u b i c n e t e r s ( m 3 ) c u b i c me te rs

To O b t a i n

i nches i nches f e e t mi 1 es

square f e e t square ' n i l es 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 g rams (mg) 0.00003527 ounces gralils ( g ) 0.03527 ounces k i l ograms ( k g ) 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 o n s k i 1 oca l o r i e s ( k c a l ) 3.965 B r i t i s h thenna l u n i t s

Cel s i u s dey rees 1.8(OC) + 32 F a h r e n h e i t degrees

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

i nches 25.40 i nches 2.54 f e e t ( f t ) 0.3048 f a thoms 1.829 m i l e s ( m i ) 1.609 n a u t i c a l m i l e s ( m i ) 1.852

square f e e t ( f t 2 ) ac res 2 squa re m i l e s (mi

ga l 1 ons ( ga 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 ( l b ) 0.4536 s h o r t t o n s ( t o n ) 0.9072 B r i t i s h thermal u n i t s ( B t u ) 0.2520

m i l 1 i m e t e r s c e n t i m e t e r s ineters me te rs k i l o m e t e r s k i 1 o ~ e t e r s

squa re me te rs hec ta res square k i l o m e t e r s

1 i t e r s c u b i c m e t e r s c u b i c me te rs

grains k i l o g r a m s m e t r i c t o n s k i 1 oca l o r i e s

F a h r e n h e i t degrees 0.5556(OF - 32) C e l s i u s degrees

CONTENTS

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . C O N V E R S I O N T A B L E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ACKNOWLEDGMENTS

. . . . . . . . . . . . . . . . . . . . . . NONMENCLATllRE /TAXONOMY /RANGE . . . . . . . . . . . . . . . . . . . . . MORPHOLOGY/IDENTIFICATION A I D S . . . . . . . . . . . . . . . . . . . . . REASON FOR I N C L U S I O N ON S E R I E S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L I F E H I S T O R Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L a r v a e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J u v e n i l e s A d u l t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GROWTH C H A R A C T E R I S T I C S . . . . . . . . . . . . . . . . . . . . . . . . COMMERCIAL S H E L L F I S H E R I E S . . . . . . . . . . . . . . . . . . . . . . . . . . P o p u 1 a t i o n D y n a m i c s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E C O L O G I C A L R O L E . . . . . . . . . . . . . . . . . . . . . . . ENVIRONMENTAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T e m p e r a t u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S a l i n i t y . . . . . . . . . . . . . . . . . . . . . . . . S u b s t r a t e a n d C u r r e n t O x y g e n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T u r b i d i t y a n d S e d i m e n t a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A c i d i t y

L I T E R A T U R E C I T E D . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ACKNOWLEDGMENTS

We thank Herber t Hidu, Professor o f Zoology, U n i v e r s i t y o f Maine; Edwin W. Cake, J r . , Head, Oyster B io logy Sect ion, Gu l f Coast Research Laboratory; Mark Chatry, Marine B i o l o g i c a l Laboratory, Louis iana Department o f W i 1 d l i f e and F i she r ies ; and Dexter S. Haven, V i r g i n i a I n s t i t u t e o f Marine Science, f o r rev iewing t h e manuscript and o f f e r i n g many h e l p f u l suggestions.

F i g u r e 1. American o y s t e r ( G a l t s o f f 1964).

AMER ICAN OYSTER

S c i e n t i f i c name . . . . . Crassos t rea v i r g i n i ca (Gmel i n )

P r e f e r r e d common name . . . American o y s t e r ( F i g u r e 1 )

Other common name . . . Easte rn o y s t e r Class . . . . . B i v a l v i a (Pelecypoda) Order . . . . . . M y t i l o i d a (P te ro i dea ) Fami l y . . . . . . . . . . . 0s t r e i dae

Geographic range: The American o y s t e r l i v e s i n e s t u a r i e s and behind b a r r i e r i s l a n d s a l o n g t h e e a s t coast o f N o r t h America, f r om t h e Gu l f o f S t . Lawrence, Canada, t o Key Biscayne, F l o r i d a . I t s range extends t o t h e Yucatan Peninsula o f Mexico and t h e West I n d i e s t o Venezuela. Th is species was s u c c e s s f u l l y i n t r oduced i n Japan, A u s t r a l i a , Great B r i t a i n , Hawai i , and t h e west coast o f Nor th A m e r i c a (Ahmed 1975 ) . I n t h e m i d - A t l a n t i c r eg ion , t h e American o y s t e r i s most abundant i n Long I s l a n d Sound, Delaware Bay, and Chesapeake Bay.

MORPHOLOGY/IDENTIFICATION AIDS

The l e f t va lve i s almost always t h i c k e r and heav ie r t h a n t h e r i g h t , and more deeply cupped (Yonge 1960; G a l t s o f f 1964). The o y s t e r i s cemented t o t h e s u b s t r a t e on i t s l e f t va lve. Hinge t e e t h a r e absent, bu t a b u t t r e s s on t h e r i g h t va lve f i t s i n t o a depress ion on t h e l e f t . There i s no gap between t h e valves when f u 1 l y c losed.

S h e l l shape i s va r i ab le . On h a r d bottoms, beaks (umbones) usua l l y a r e curved and p o i n t toward t h e p o s t e r i o r , whereas i n s i l t y environments o r on ree fs , umbones a r e u s u a l l y s t r a i g h t . S i n g l e oys te r s f r om ha rd subs t ra tes a re rounded and ornamented w i t h r a d i a l r i dges and f o l i a t e d processes ( F i g u r e I ) , whereas those f rom s o f t subs t ra tes o r r e e f s a r e more s l e n d e r and a r e spa rse l y ornamented. She1 1 t h i ckness a1 so depends on e n v i ronment . Oysters on ha rd subs t ra tes 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 t han those on s o f t subs t ra te . The index o f shape ( h e i g h t + w i d t h / l e n g t h ) va r i es f r om 0.5 t o 1.3

i n sou the rn p o p u l a t i o n s and f r om 0.6 t o 1.2 i n n o r t h e r n popu la t i ons .

The s h e l l grows a long a d o r s a l - v e n t r a l ax i s , b u t t h e ang le o f t h e a x i s i s n o t pe rmanen t and may change seve ra l t imes d u r i n g t h e l i f e s p a n o f 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 degrees. The s h e l l i s u s u a l l y 10 t o 15 cm l o n g when t h e o y s t e r i s 3 t o 5 yea rs o l d . 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 inues t o grow, p r i m a r i l y i n th i ckness , ove r t h e l i f e s p a n o f t h e o y s t e r (S tenze l 1971).

The American o y s t e r i s monomya- r i a n ( a n t e r i o r adduc to r muscle has been l o s t ) . 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 v e n t r a l . A second muscle scar , o f t h e Quens ted t ' s muscle, i s s i t u a t e d v e n t r a l t o and a s h o r t d i s t a n c e f r o m t h e h inge. The p u r p l e p i gmen ta t i on on t h e adduc to r muscle s c a r 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 o m s i m i l a r spec ies. I n t h e mangrove o y s t e r (5. r h i z o horae) and P a c i f i c o y s t e r (C.

t e muscle sca r i s 1 i g h t i y & pigmented and i n C. r i v u l a r i s i t i s unpigmented. T r e s h e l l o f t h e mangrove o y s t e r i s l e s s p l i c a t e d t h a n t h a t of t h e American oys te r . There a r e no o t h e r spec ies o f Crassos t rea sympa t r i c w i t h t h e American o y s t e r i n t h e Mid-At l a n t i c r eg i on . Species of Crassos t rea a r e d i y t i ngu i shab ' l e f rom spec ies o f Os t rea spec ies by t h e p r o - myal chamber, which i s w e l l developed i n C r a s s o s t r e a s p e c i e s , b u t n o t i n Ostrea. By t r a p p i n g s a l t water , t h i s chamber may a l l o w t h e American o y s t e r t o t o l e r a t e w i d e r f l u c t u a t i o n s i n s a l i n i t y i n es tua r i es .

Crassos t rea spec ies a r e ov iparous (gametes a r e r e l eased i n t o t h e wate r ) , whereas Ost r ea spec ies i ncuba te f e r t i l i z e d eggs i n t h e mant le c a v i t y . Advanced l a r v a e of American oys te r s a re d i s t i n g u i s h e d f r o m t h e l a r v a e o f o t h e r b i v a l v e s by l eng th -w id th 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 o f t h e l a r v a e o f t h e American o y s t e r i s d i s t i n c t l y d i f f e r e n t f rom t h a t i n o t h e r b i v a l ves ( Lu t z e t a1 . 1982).

REASON FOR INCLUSION I N SERIES

The American o y s t e r suppor ts an impo r t an t commercial f i s h e r y f r o m t h e G u l f o f S t . Lawrence t o t h e Gu l f o f Mexico, and i s an impo r t an t m a r i c u l - t u r e spec ies. More oys te r s a r e processed t han any o t h e r s i n g l e f i s h e r y p roduc t i n t h e U n i t e d S ta tes , and o v e r 10,000 p e o p l e work i n t h e o y s t e r i n d u s t r y . Oysters a r e va lued as a l u x u r y f o o d i tem. The American o y s t e r i s t h e keys tone spec ies of a r e e f b iocoenos is t h a t i n c l udes seve ra l hundred spec ies (We1 1s 1961). Because t h e o y s t e r i n h a b i t s e s t u a r i e s , i t i s p a r t i c u l a r l y vu l he rab le t o u rban and i n d u s t r i a l d i s tu rbances .

LIFE HISTORY

Gametogenesis and spawning a r e s t i m u l a t e d by changes i n wa te r tem- p e r a t u r e (Kaufman 1978; Andrews 1979a, 1979b; Kennedy and K ran t z 1982b). Spawning temperatures d i f f e r among popu la t i ons . Based on spawning temperature, Stauber (1950) recogn ized t h r e e phys i 01 og i c a l races, one from t h e G u l f o f Mexico t h a t spawns when wate r temperatures a re near 25 O C , and two f r o m t h e eas t coas t t h a t spawn a t 16 O C and 20 O C . Evidence f o r p h y s i o l o g i c a l races a l s o was r e p o r t e d by Loosanof f (1969), who found t h a t gametes o f 60% o f t h e o y s t e r s f r o m Long I s l a n d Sound p o p u l a t i o n s r ipened a t a wa te r tempera tu re of 15 O C a f t e r 45 days, whereas o n l y 20% o f t h e oys te 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 temperature. A t 18 O C none of t h e oys te r s sou th o f New Jersey matured i n a h o l d i n g pond i n Connec t i cu t , even a f t e r 3 years. I n Barnegat Bay, New Jersey, oys te r s f i r s t spawn when wate r tempera tu re reaches 20 OC, b u t subsequent spawning

r e q u i r e s wate r temperatures o f a t l e a s t 22 "C (Nelson 1928). I n Dela- ware, n a t i v e o y s t e r s matured i n 150 days a t 15 "C ( P r i c e and Maurer 1971), which i s a much l onge r t i m e t han t h a t r e p o r t e d by L o o s a n o f f ( 1 9 6 9 ) . The days r e q u i r e d f o r gonad ma tu ra t i on (D) i n Long I s l a n d Sound o y s t e r s a r e i n v e r s e l y p r o p o r t i o n a l t o temperature (T i n "C):

Delaware oys te r s r e q u i r e s i x t imes as l o n g t o r i p e n a t wa te r temperatures f r o m 12 t o 20 O C as do Long I s l a n d Sound o y s t e r s ( P r i c e and Maurer 1971). I n Chesapeake Bay, spawning occurs when water temperatures a r e 21 t o 24 "C, w i t h l i m i t e d spawning a t 15 t o 20 "C (Kennedy and Kran tz 1982).

The v a r i a t i o n i n spawning t e m p e r a t u r e may be caused by o t h e r f a c t o r s . Kennedy and Kran tz (1982) p o s t u l a t e d t h a t phy top lank ton blooms and n u t r i t i o n may be respons ib l e f o r s t i m u l a t i n g spawning i n Chesapeake Bay oys te r s .

The t i m e and i n t e n s i t y o f spawning do n o t depend d i r e c t l y on t i d a l c yc l es (Loosanoff and Nomejko 1951). Du r i ng low t i d e , however, t h e s u n l i g h t may warm t h e wate r and s t i m u l a t e spawning (Dr innan 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 t h a t r e l ease t h e i r sperm and a pheromone i n t o t h e water. The f e m a l e s spawn when sperm e n t e r t h e wate r t r a n s p o r t system (Andrews 1979a), o r when pheromone s t i m u l a t e s f e m a l e s t o r e l e a s e t h e i r eggs i n a mass spawning (Bahr and Lanie.r 1981). Each female produces 23 m i l l i o n t o 86 m i l l i o n eggs p e r spawning; t h e number i s 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). I n d i v i d u a l f e 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 we re c i t e d by Yonge ( 1 9 6 0 ) . Females may spawn s e v e r a l t imes i n one season; as t h e i n t e r v a l between spawnings increases, t h e

number o f eggs p r o d u c e d p e r season decreases (Davis and Chanley 1955). The q u a n t i t y o f sperm produced depends on t h e q u a n t i t y of s t o r e d glycogen of t h e male o y s t e r a t t h e beg inn ing o f t h e spawning season (Loosanoff and Davis 1952).

The spawning season i s l onge r i n warmer c l ima tes : f r om A p r i 1 t o October i n t h e G u l f o f Mexico (Hayes and Men- z e l 1981); but o n l y i n J u l y near P r i n c e Edward I s l a n d , Canada ( D r i nnan and S t a l l w o r t h y 1979). I n Long I s l a n d Sound, spawning begins around J u l y 1 and l a s t s i n t o August (Loosanof f and Nomejko 1 9 5 1 ) . I n Chesapeake Bay, Maryland, spawning i s f rom May t o September; oys te r s i n sha l lower wate r spawn f i r s t (Beaven 1955). Oysters a t an unusual depth o f 40 m i n c o o l e r waters o f Patuxent R i v e r es tuary do no t r e l ease a1 1 t h e i r gametes d u r i n g t h e spawning season (Me r r i 11 and Boss 1966). Kennedy and K ran t z (1982) documented t h e spawning season f o r 18 beds i n Chesapeake Bay. Spawning begins i n May i n some beds, and June i n others. Spawning con t inues i n t o August i n most beds and i n t o September i n a f e w ( t o December i n one bed ) . The spawning season i n eas te rn shore b a r s e x t e n d e d o v e r a l o n g e r p e r i o d d u r i n g t h e e a r l y 1960s t han i n 1977 t o 1978. I n t h e James R i v e r e s t u a r y , V i r g i n i a , spawning commences i n l a t e May and con t inues u n t i 1 October (Loosanof f 1932). The eggs ha tch about 6 hours a f t e r f e r t i l i z a t i o n a t wa te r temperatures near 24 "C (Loosanof f 1965a).

Larvae

Oys te r l a r v a e a r e meroplanktoni c and remain i n t h e wate r column f o r 2 t o 3 weeks a f t e r h a t c h i n g (Bahr and L a n i e r 1981). I n M i l f o r d Harbor, Connec t i cu t , t h e l a r v a l p e r i o d i s 13 t o 16 days a t 22 "C (Pry therch 1929). Du r i ng t h e p l a n k t o n i c phase, t h e l a r v a e pass th rough seve ra l stages 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 sec re tes a s t r a i g h t - h i nge s h e l 1 and develops a r i n g o f locomotory c i l i a c a l l e d t h e velum. T h i s prod issoconch I l a r v a ( a l s o termed s t r a i g h t - h i n g e l a r v a o r v e l i g e r ) i s about 75 urn i n d iameter . It develops i n t o t h e p ro - d issoconch I 1 l a r v a ( a l s o termed eyed l a r v a o r p e d i v e l i g e r ) , which i s char- a c t e r i z e d by pronounced umbones. Th i s l a r v a i s a v igo rous swimmer, and has a p a i r o f p igmented eyes and an e l on - gated f o o t w i t h a l a r g e byssa l g land (Andrews 1979a). The p r o d i ssoconch l a r v a i s a b o u t 0.3 mm i n d i a m e t e r ( G a l t s o f f 1964).

Young l a r v a e (prod issoconch I ) i n L i t t l e Egg Harbor, New Jersey, s t a y i n t h e wa te r column about 1.0 m below t h e s u r f a c e ( C a r r i k e r 1951). O lde r 1 a rvae (prod issoconch 11) a r e near t h e bo t tom i n t h e h a l o c l i ne 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 neare r t h e s u r f a c e d u r i n g t h e ebb t i d e . The l a t e s t age l a r v a e congregate near t h e bo t tom o f Delaware Bay d u r i n g s l ack t i d e and a r e d i s t r i b u t e d th roughou t t h e wa te r column d u r i n g f l o o d t i d e (Kunkle 1957). Andrews (1979a) doubted t h e v a l i d i t y o f t hese f i n d i n g s . I n t h e l a b o r a t o r y , o l d e r l a r v a e a re s t i m - u l a t e d t o swim by inc reased s a l i n i t i e s and i n h i b i t e d by decreased s a l i n i t i e s (Hask in 1964). La rvae a r e on t h e b o t - tom o f M i l f o r d Harbor, Connec t i cu t , when t h e c u r r e n t i s g r e a t e r t han 0.6 m/sec and drop t o t h e bo t tom i n h o l d i n g t anks a t v e l o c i t i e s o f 0.3 t o 0.5 m/sec (P r y t he r ch 1929). Swimming v e l o c i t y inc reases by t h r e e f o l d a t a s a l i n i t y near 100% seawater (Hidu and Hask in 1978). Upward swimming i s a t about 1 cm/sec (Wood and Harg is 1971; Andrews 1979a). These behav io ra l t r a i t s may 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 so t h a t l a r v a e a v o i d be i ng f l u shed f r o m t h e es tua r y . Genera l l y , l a r v a e a r e t r a n s p o r t e d toward t h e head of an es tua r y a g a i n s t a n e t downstream f l o w ( S e l i g e r e t a l . 1982) by u s i n g t hese behav io ra l responses.

Juveni l e s --

Two t o t h r e e weeks a f t e r spawning, o y s t e r l a r v a e seek a s o l i d s u r f a c e f o r a t tachment ( c a l l e d a s e t , o r t h e process o f s e t t i n g ) and com- mence c raw l i ng i n c i r c l es (Andrews 1979a ) . I n Long I s l a n d Sound, t h e f i r s t s e t i s 18 days a f t e r t h e f i r s t spawning (Loosanof f and Nomejko 1951). A f t e r a t t a c h m e n t w i t h a d r o p l e t o f 1 i q u i d cement exuded f r o m a po re i n t h e f o o t , t h e y l o s e t h e velum and f o o t and a r e now c a l l e d spa t (newly a t t ached o y s t e r s ) . S h e l l s a r e p r e f e r r e d as at tachment , bu t s tones and o t h e r f i r m su r f aces 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 han t hose s e t t i n g l a t e r (Losee 1979). Metamorphosis may be de layed i f s u i t - a b l e s u b s t r a t e i s n o t l o c a t e d (Newki r k e t a l . 1977). Burke (1983) d e f i n e d s e t t l e m e n t as t h e behav io r of d ropp ing t o t h e bottom, i n c o n t r a s t t o metamorphosis, which i s t h e i r r e v e r s i b l e developmental process.

Severa l f a c t o r s i n f l u e n c e t h e s e t t i n g behav io r o f l a rvae . Hidu and Hask in (1971) suggested t h a t r i s i n g t enpe ra tu res over t i d a l f l a t s d u r i ng f l o o d t i d e s s t i m u l a t e s e t t i n g . I n t h e 1 abo ra to r y , r i s i n g tempera tu re t r i g g e r e d s e t t i n g ( L u t z e t a1 . 1970). Swimming l a r v a e have p o s i t i v e photo- t a x i s , which becomes n e g a t i v e w i t h an i nc rease i n tempera tu re (Bahr and L a n i e r 1981). L i g h t i n h i b i t s s e t t i n g i n h o l d i n g tanks (Shaw e t a l . 1970) and o y s t e r s p r e f e r t o s e t on t h e unders ides o f s h e l l s ( R i t c h i e and Menzel 1969). More o y s t e r s s e t t l e i n t h e s u b t i d a l zone t han e lsewhere i n Delaware Bay (Hidu 1978).

Oys te r l a r v a e u s u a l l y s e t i n e s t a b l i s h e d o y s t e r beds o r where s h e l l s u b s t r a t e i s p resen t . C r i s p (1967) p o s t u l a t e d t h a t 1 a rvae a r e a t t r a c t e d t o t h e p ro te inaceous s u r f a c e o f t h e pe r i os t r acum o f a d u l t she l 1s and observed t h a t l a r v a e d i d n o 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 waterborne f a c t o r , perhaps a pheromone, s t i m u l a t e s l a r v a e t o s e t t l e on o y s t e r s h e l l s . Cur ren ts 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 : se t t l emen t i n Delaware Bay i s heav ies t where t i d a l c u r r e n t s c u t through s a l t marshes (Keck e t a l . 1973). A l though h i g h s a l i n i t i e s s t i m u l a t e se t t l emen t , m o r t a l i t y inc reases because o y s t e r p reda to rs a re more numerous a t h i g h s a l i n i t i e s (Ulanowicz e t a1 . 1980). Howeverythe number o f a d u l t spawners i s n o t c o r r e l a t e d w i t h t h e d e n s i t y o f spa t produced (MacKenzie 1983). R e d u c t i o n i n t h e q u a n t i t y of f r e s h s h e l l s and widespread s i l t a t i o n l i m i t s t h e h a b i t a t s u i t a b l e f o r s e t t i n g i n most o y s t e r beds i n t h e m i d - A t l a n t i c r eg ion (MacKenzie 1983).

The t i m e o f s e t t l e m e n t v a r i e s among l o c a t i o n s and i s g e n e r a l l y s h o r t e r t han t h a t o f spawning. I n t h e N i a n t i c R i v e r es tuary , Connec t i cu t , most l a r v a e s e t t l e d i n J u l y and a few i n August (Ma rsha l l 1959). I n Long I s l a n d Sound, se t t l emen t i s f rom m i d - J u l y t o e a r l y Augus t and a g a i n from l a t e August th rough September (Loosanof f 1966). Large numbers o f l a r v a e sometimes d i e i n mid-summer, perhaps because o f blooms of d i n o f l a g e l l a t e s . I n Delaware Bay, l a r v a e s e t t l e f rom around J u l y 4 t o e a r l y September (Maurer e t a l . 1971). Peaks i n s e t t i n g i n t h e f i v e t r i b u t a r i e s s t u d i e d occur red mos t l y i n J u l y . I n Chesapeake Bay, Maryland, s e t t i n g i s f rom May t o October w i t h a two-week peak, u s u a l l y i n J u l y (Beaven 1955). D i f f e r e n t t r i b u t a r i e s i n Chesapeake Bay have peaks a t d i f f e r e n t t imes : J u l y i n t h e S t . Mary 's R i ve r , I s l a n d Bar and Ho l l and S t r a i t s ; Ju ly , August and September i n bars i n t h e open bay; August and September a t Wreck Shoal; and J u l y and September a t York town F i s h P i e r and Page's Rock (Andrews 1951). I n t h e James R i v e r es tuary , V i r g i n i a , se t t l emen t was f rom mid-June t o mid-October w i t h peaks i n mi d-August and mid-September (Loosa- n o f f 1932).

Adu 1 t s

Because a d u l t oys te rs a r e sess i l e y 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 v a e s e t and on subsequent s u r v i v a l o f t h e spat . Oysters t y p i - c a l l y l i v e i n clumps c a l l e d r e e f s o r beds, i n which t hey a r e t h e dominant organisms. The mass o f s h e l l s some- t imes a l t e r s t h e cu r ren t s , and increases d e p o s i t i o n o f p a r t i c u l a t e s s o t h a t t h e l o c a l environment i s modi- f i e d .

A d u l t s a r e o f t en d ioec ious , bu t a l s o o f t e n change gender as p ro tandrous hermaphrodi tes (Bahr and L a n i e r 1981 ) . The gender and t h e process o f sex i n v e r s i o n a r e genet i - c a l l y determined by perhaps t h r e e l o c i ( H a l e y 1977 ) . T y p i c a l l y t h e y o u n g a d u l t s a r e p redomina te ly males; subsequent sex i n v e r s i o n w i t h age i n - creases t h e number o f females. Sex r a t i o s i n t h e James R i v e r E s t u a r y , V i r g i n i a , change f r o m 90% males a t 1 yea r o f age t o 80% females i n o l d e r oys te r s (Andrews 1979a).

GROWTH CHARACTERISTICS

Oysters grow f a s t e s t d u r i n g t h e i r f i r s t 3 months o f l i f e (Bahr 1976). I n t h e i r second y e a r , j u v e n i l e s i n De lawa re Bay t h a t we re 11 t o 14 mm l o n g 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). Whole body we igh t inc reased f rom 0.23 g t o 4.0 g i n those months. I n a r e v i e w o f g r o w t h r a t e s i n t h e American oys te r , I n g l e and Dawson (1952) c i t e d t h e f o l l o w i n g s i z e s a t corresponding age: 35 t o 75 mm i n 6 mo and 100 t o 125 mm a t 4 y e a r s i n Long I s l a n d Sound; 95 t o 106 mm a t 1 y e a r i n New Jersey; 21 mm a t 44 days, 40 mn a t 12 mo, and 90 mm a t 23 mo i n Chesapeake Bay. Oysters i n t h e deep c o o l w a t e r s o f Chesapeake Bay grow s l owe r t han t hose i n sha l l ow warmer waters ( M e r r i l l and Boss 1966). I n t h e V i r g i n i a p a r t o f Chesapeake Bay oys te r s weigh 24 g a t t h e end o f t h e

f i r s t year , 90 g a t y e a r 2, 105 g a t 3 years , and 190 g a t y e a r 4 (Andrews and McHugh 1957). Instantaneous month ly growth c o e f f i c i e n t s range f r o m 0.42 t o 0.84 ( G i l l m o r 1982). I n t h e m i d - A t l a n t i c reg ion , t h e minimum marke tab le s i z e o f 90 mm i s a t t a i n e d i n 2 t o 5 years.

The growth r a t e of t h e o y s t e r i s 1 a r g e l y governed by tenpera tu re , 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 ceases d u r i n g w i n t e r , except i n F l o r i d a , where growth i s cont inuous th roughout t h e y e a r ( B u t l e r 1 9 5 2 ) . Growth o f V i r g i n i a oys te r s i s s low and t h e con- d i t i o n f a c t o r i s low d u r i n g spawning because energy i s used f o r gamete p r o d u c t i o n i n s t e a d o f p r o d u c t i o n of body biomass (Haven 1962). Oysters expend 48% o f t h e i r annual energy budget i n r ep roduc t i on (Dame 1976). A f t e r spawning, F l o r i d a oys te r s ga in we igh t be fo re t hey i nc rease i n l e n g t h ( B u t l e r 1952). Growth o f oys te r s i n Long I s l a n d i s g r e a t e s t i n August and September a f t e r spawning, when glycogen reserves a re r e s t o r e d (Loosanof f and Nomejko 1949; P r i c e e t a l . 1975).

Envi ronmenta l c o n d i t i o n s a f f e c t g row th . O y s t e r s i n a s a l t pond on Long I s l a n d i n f l u c t u a t i n g s a l i n i t y grow f a s t e r t han those under r e l a t i v e l y u n i f o r m s a l i n i t y ( P i e r c e and Conover 1954). Oysters i n Maine exposed f o r a r e l a t i v e l y s h o r t t i m e d u r i n g t h e t i d a l c y c l e grow a t about t h e same r a t e as t hose con t i nuous l y submerged (Gi 1 lmor 1982). Long expos- u r e t o t h e atmosphere, however, reduces growth; those exposed 20% o f t h e t i m e 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 phy top lank ton dens i t y , and some o f t h e observed d i f f e r e n c e s i n r a t e s o f growth l i k e l y a re caused by changes i n phy top lank ton compos i t ion and abundance. I r, South Ca ro l i na , oys te r s grow f a s t e r i n n u t r i e n t - r i c h s a l t ponds t h a n i n t i d a l creeks where p r ima ry p r o d u c t i v i t y i s lower (Manzi e t a l . 1977). A Walford

p l o t p r e d i c t s t h a t oys te r s i n South C a r o l i n a would cease growing when 140 mm long (Dame 1971); however, oys te r s 200 mn long occur.

COMMERCIAL SHELLFISHERIES

The Amer i can o y s t e r has t r a d i - t i o n a l l y suppor ted a va luab le i n d u s t r y a1 on t h e eas te rn seaboard (MacKenzi e 19833 . Today, t h e comnercial areas i n t h e M i d - A t l a n t i c r e g i o n ( F i g u r e 2 ) a r e i n Long I s l a n d Sound, bays a long t h e New Jersey coast, Delaware Bay, bays a long t h e coast o f Maryland and V i r g i n i a , Chesapeake Bay, and A1 bemarle Sound o f Nor th Caro l i na. Landings have decreased f r o m about 100 m i l l i o n l b d u r i n g t h e 1920's (Mat th iessen 1969) t o about 25 mi 11 i o n 1b s i n c e t h e 1960's (Tab le 1 ) . Oyster land ings have remained r e l a t i v e l y s t a b l e i n Chesapeake Bay from 1950-1982, whereas 1 andi ngs i n t h e r e s t o f t h e mid-At1 a n t i c r e g i o n have f l u c t u a t e d more t han 10 f o l d (Tab le 1 ) ; o y s t e r p roduc t i on d e c l i n e d s t e e p l y i n Chesapeake Bay i n 1983-84. Maryland and V i r g i n i a a r e t h e l e a d i n g producers o f oys te r s f o l l o w e d by New York (Tab le 2 ) . Annual land ings i n New York and New Jersey have f l u c t u a t e d as much as 50%, b u t i n Connec t i cu t t h e annual 1 andings have f l u c t u a t e d f rom 136,000 1b t o 1 m i l l i o n I b , and i n Delaware f r o m 8,000 t o 501,000 I b . I n Long I s l a n d Sound, p e r s i s t e n t s e t f a i l u r e i s r espons ib l e f o r t h e d e c l i n e i n land ings s i n c e 1920 (Mat th iessen 1969). A r e d u c t i o n i n t h e s p r e a d i n g o f s h e l l s due t o an inc rease i n t h e s a l e o f oys te r s i n t h e s h e l l i s p a r t i a l l y r espons ib l e f o r t h e d e c l i n e i n abundance o f o y s t e r s i n Long I s 1 and Sound (MacKenzie 1983).

Oys te rs a re t aken by handp ick ing o f clumps f rom ree f s (Bahr and L a n i e r 1981), hand and pa ten t t o n g i n g f r om boats, and d ragg ing and d redg ing f r om boats ( K o r r i nga 1976). Dredging has made c a p t u r e more e f f i c i e n t b u t i t a l s o inc reases t h e p o t e n t i a l f o r overharves t and d e p l e t i o n of o y s t e r

ATLANTIC OCEAN

MILES

K ILOMETERS

F igu re 2. Commercial p roduc t ion areas fo r t h e American o y s t e r i n t h e mid-At lan t ic .

7

T a b l e 1. O y s t e r l a n d i n g s ( t h o u s a n d s o f pounds meat w e i g h t ) by geographica l r e g i o n f o r t h e years 1950-1982. U.S. Dep . Commerce, NOAA, Na t l . Mar. F ish . Serv., N a t l . F ish . S t a t i s t i c s Program. Annual summaries o f o y s t e r land ings , 1950-1982.

South G u l f o f Year New England Mid-At1 a n t i c Chesapeake Atlantic Mexico

beds. Ha rves t i ng by d i v e r s has become impo r tan t i n Mary land waters.

The American o y s t e r i s t h e dominant s h e l l f i s h i n m a r i c u l t u r e i n t h e U n i t e d S ta tes . I n 1980, t h e y i e l d o f c u l t u r e d oys te r s was 23 m i l l i o n l b va lued a t $37 m i l l i o n . Th is p r o d u c t i o n i s equal t o 55% o f t h e 1980

U.S. o y s t e r landings. Seed oys te r s a r e a l s o harves ted f o r t r a n s p l a n t i n g t o wate r w i t h i n s u f f i c i e n t n a t u r a l s e t t i n g . About 99% o f t h e U.S. seed p r o d u c t i o n comes f r o m V i r g i n i a waters ( A l f o r d 1975).

The equiva lences between d i f f e r - e n t values r e p o r t e d f o r ha rves t are: 1

Tab le 2. Landings (thousands o f pounds) o f American o y s t e r meats i n t h e m i d - A t l a n t i c S ta tes 1977-1982. U.S. Department o f Commerce, NOAA, Na t l . Mar. F i sh . Serv., N a t l . F ish . S t a t i s t i c s Program. Annual summaries o f o y s t e r land ings .

S t a t e Mid- A t l a n t i c

Year C T N Y NJ D E MD V A t o t a l U.S. t o t a l

bu = 34 1 = 32 k q t o t a l weiqht = 7.8 p i n t s = 3.4 k g meat we igh tv ( P r u d e r 1975).

The market q u a l i t y o f oys te rs depends on t h e meat s i z e and t a s t e , which vary w i t h t h e season. I n F l o r i d a , t h e y i e l d o f o y s t e r meats p e r s h e l l i s best i n March j u s t be fo re spawning and lowest i n t h e summer months d u r i n g spawning (Rockwood and Mazek 1977). I n t h e lower Chesapeake Bay, meat y i e l d s a r e bes t i n June and aga in i n October and November (Dex te r S. Haven, V i r g i n i a I n s t . o f Mar. Sci., pers . comm.). The reduced y i e l d s i n summer correspond t o a reduced c o n d i t i o n index f o l l o w i n g spawning (Hopk ins e t a l . 1954; Lawrence and S c o t t 1982). Glycogen, which g ives oys te r s t h e i r sweet t a s t e , i s h i ghes t i n f l e s h o f Maryland oys te r s i n A p r i l and May j u s t be fo re spawning (S idwe l l e t a l . 1979).

Popu 1 a t i on Dynami cs

The vast m a j o r i t y of t h e eggs and l a r v a e produced by American oys te rs p e r i s h be fo re s e t t i n g . F o l l o w i n g spawning, o y s t e r l a r v a e a re abundant p l a n k t e r s ; d e n s i t i e s have ranged f rom 2,000 t o 5,500lk l i n V i r g i n i a coas ta l waters (Andrews 1979a; Sel i g e r e t a1 . 1982), 100 t o 17,000lkl i n Long I s l a n d Sound (Loosanof f and Nomejko 1951),

and 24,000lkl i n Gard iners Bay o f Long I s l a n d Sound ( C a r r i k e r 1959) and i n t h e deeper waters o f Delaware Bay (Hidu and Haskin 1971). The concen- t r a t i o n o f l a r v a e near shore i n Delaware Bay was o n l y 1,000lkl . Abundance was g r e a t e r a f t e r h i g h t i d e i n t h e James R i v e r Es tuary i n V i r g i n i a (Andrews 1979a). I n t h e St . Mary 's R i v e r Es tuary i n Mary land t h e numbers p e r k i l o l i t e r were 2,000 t o 5,000 s t r a i g h t - h i n g e la rvae , 100 t o 1,000 e a r l y umbo la rvae , and 50 t o 200 l a t e umbo larvae (Manning and Whaley 1955).

The d a i l y m o r t a l i t y o f l a r v a e i n Canada was about 10% (Dr innan and S t a l l w o r t h y 1979 ) , and f o r s p a t i n Massachusetts was about 90% monthly (Kran tz and Chamber1 i n 1978).

The d e n s i t y o f n e w l y s e t s p a t f l u c t u a t e s g r e a t l y f r o m y e a r t o y e a r and i s d i f f e r e n t even i n ad jacen t areas. Repor ted d e n s i t i e s range f r om 0.35-500 spat /shel 1 (Andrews 1949, 1955; Loosanof f and Nomejko 1951; C a r r i k e r 1959; Webster and Shaw 1968; Kennedy 1980). Typ i ca l l y t h e r e have been 60 spat/bu o f n a t u r a l s h e l l s (range 0.6 t o 72/bu) i n t h e Mary land p o r t i o n of Chesapeake Bay (Kran tz and Mer i tt 1977 ) .

S u r v i v a l o f spa t i n Long I s l a n d Sound ranged f r o m 0 t o 14% i n t h e i r

f i r s t summer o f l i f e (Loosanof f and Engle 1940). Spat m o r t a l i t y a f 50% t o 70% i n Delaware Bay was reduced t o 30% t o 40% when s p a t were p r o t e c t e d by screens f r om 1 a rge r p reda to rs (Tweed 1973). S u r v i v a l o f spa t t o seed (3 t o 4 months) i n Eas te rn Bay, Maryland, was l ess than 10% (Engle 1956). S u r v i v a l i n e s t u a r i e s o f t h e Choptank R iver , Maryland, ranges f r o m 1 t o 27% th rough t h e f i r s t season (Webster and Shaw 1968 ) . O f 314 s p a t p e r s h e l l t h a t s e t t l e d , o n l y 14 were s t i l l a l i v e a t t h e end o f t h e season i n t h e James R i v e r es tuary , V i r g i n i a (Andrews 1 9 4 9 ) . Spa t s u r v i v a l was l e s s i n dense se t s t h a n i n sparse s e t s i n t h e James R i ver, V i r g i n i a (Andrews 1955) and i n Chesapeake Bay (Webs te r and Shaw 1968). The number o f seed p e r square meter i n Long I s l a n d Sound was 200 t o 10,000; f o r 1- t o 2-year-o lds i t was 300; and f o r 3- t o 4-year-o lds i t was 75 (MacKenzie 1981).

The p o p u l a t i o n d e n s i t y o f oys te rs i n Delaware Bay was about 70 bu/acre i n n a t u r a l beds and f r o m 10 t o 375 bu/acre i n p l a n t e d beds (Maurer e t a1 . 1971). The d e n s i t y o f 70 bu/acre was about 80 kg/ha, i n c l u d i n g s h e l l , o r about 800 oysters/ha, assuming an average weight o f 100 g. I n Chesapeake Bay, t h e d e n s i t y was about 70 b u / a c r e i n n a t u r a l beds and 500 bu/acre i n p l a n t e d beds (D. S. Haven, pers . comm. ) .

Ameri can oys te rs t h a t s u r v i ve t h e i r f i r s t y e a r o f l i f e a re s u b j e c t t o r e l a t i v e l y l i t t l e m o r t a l i t y except t h a t i n f l i c t e d by she1 l f i she rmen o r caused by d isease outbreaks. I n Long I s l a n d Sound t h e annual n a t u r a l m o r t a l i t y o f a d u l t s was o n l y 4%, e.g., 77% s u r v i v e d a f t e r 4 years (MacKenzie 1981). A d u l t s u r v i v a l i n South Caro- l i n a was 85% i n a s a l t pond and 40% i n an es tua ry (Manzi and B u r r e l l 1977). Mo r ta l i t y was s i z e dependent. Mo r ta l - i t y o f adu l t s 25 t o 50 mm l o n g was 19% p e r month i n summer (28% i n J u l y ) , b u t those 50 t o 75 mm l ong were l o s t a t t h e r a t e of 5% p e r month (near 0% i n J u l y ) and t h o s e g r e a t e r t h a n

7 5 m l o n g d i e d a t a r a t e o f l e s s than 1% p e r month (Dame 1976). S u r v i v a l was 100% i n areas p r o t e c t e d from heavy waves i n Nor th Caro l ina , and 50% p e r month i f exposed t o r e l a t i v e l y heavy waves (Ortega 1981). M o r t a l i t i e s were much h i g h e r i n t h e areas o f Delaware Bay and l o w e r Chesapeake Bay where oys te rs were i n f e c t e d w i t h MSX disease ( Andrews 1968).

ECOLOGICAL ROLE

Oys ter l a r v a e feed l a r g e l y on p lankton, p a r t i c u l a r l y smal l , naked f l a g e l 1ates (Chrysophyta) , accord ing t o G u i l l a r d (1957). A t moderate temperatures l a r v a l growth i s bes 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 temperatures above 27 O C

naked a1 gae a r e s c a r c e and c h l o r o - phytes a re much more abundant as food [Davis and Cal abrese 1964). The ia rvae , u n l i ke adu l t s , do no t consume b a c t e r i a (Davis 1953). Oyster 1 arvae a r e food f o r a wide v a r i e t y o f f i l t e r feeders (Andrews 1979a).

Adu l t oys te rs f i l t e r l a r g e q u a n t i t i e s o f b rack i sh water and remove naked f l a g e l l a t e s . They most e f f e c t i v e l y f i l t e r p a r t i c l e s i n t h e 3- t o 4 - ~ m s i z e range (Haven and Morales- Alamo 1 9 7 0 ) . F o r each gram o f d r y weight of t i s s u e , an o y s t e r h e l d a t 21 O C f i l t e r s 1.5 l / h r (Palmer 1980). A t somewhat h i g h e r temperatures about 8 l / h r a r e f i l t e r e d (Lange foss and Maurer 1975). The volume o f water f i l t e r e d p e r hour was 1,500 t imes t h e volume of t h e o y s t e r ' s body (Loosanof f and Nomejko 1946). The f i l t r a t i o n r a t e i s independent o f t h e a v a i l a b l e food supply , t h e s tage o f t i d e , o r t ime o f day. I f food i s absent, however, t h e va lves a r e c l osed most o f t h e t ime (H igg ins 1980). I n Chesapeake Bay, oys te rs inges ted t h e predominate d iatom p lank ton which changes seasona l l y (Morse 1945). D i n o f l a g e l l a t e s , ost racods, smal l eggs, and t e r r e s t r i a l p o l l e n were a l s o ingested.

The o y s t e r i s t h e dominant spec ies o f a d i v e r s e community i n b rack i sh waters . Over 40 macrofaunal spec ies o r groups l i v e i n o y s t e r beds (Bahr and L a n i e r 1981) and t h e number of spec ies i n an o y s t e r c o m n i t y sometimes exceeds 300 (We l l s 1961). Oysters were r espons ib l e f o r 88% o f t h e r e s p i r a t i o n of an o y s t e r r e e f (Bahr and L a n i e r 1981).

O y s t e r s h a v e a v a r i e t y o f d i s - eases and p a r a s i t e s and a r e p r e y e d uDon bv seve ra l ca rn i vo res ( G a l t s o f f 1964). " The b a c t e r i a ~ i b r i o and Pseudomonas sometimes k i 11 oys te rs . I n t h e l a b o r a t o r y V i b r i o e x o t o x i n a t 47 ~ g / 1 k i 1 1s o y s t e r e m b r y o s w and Roland 1984). The p ro tozoan pathoqen P e r k i nsus mar i num i n'fects oys te r s f ;om Delaware t o Mexico. The h a p l o s p o r i d i a n p ro tozoan M i n c h i n i a n e l s o n i i s respons i b l e f o r t h e d i s e a s e m d M i n c h i n i a c o s t a l i s f o r SSO (seas ide organism) ( A n d r e w s 1979b; . . 1982a). ~ i n c h i n i a n e l s o n i , common f r om Nor th C a r o l i n a t o Massachusetts (Kran tz e t a1 . 1972), caused e x t e n s i v e o y s t e r m o r t a l i t y i n t h e Delaware Bay i n 1957 and i n Chesapeake Bay i n 1960 (Andrews 1968). It a l s o k i l l e d l a r g e numbers o f oys te r s i n t h e bays a l o n g t h e coas t o f Mary land and V i r g i n i a i n 1960 (Rosenf i e l d 1971).

P reda to r s o f t e n l i m i t t h e abundance o f oys te rs , e s p e c i a l l y i f s a l i n i ti es a r e above 15 p p t (MacKenzi e 1983). I n t h e m i d - A t l a n t i c reg ion , t h e gas t ropod o y s t e r d r i 11s (Urosa l i n x c i n e r e a and Eupleura cau- d sou the rn o y s t e r d m ( T h a i s haemastoma), t h e whelk (Busycon cana l i cu l a t um) , t h e s t a r f i s h ( A s t e r i a s f o r b e s i ) , and t h e c r a b (Cancer i r r o r - a tus, C a l l i n e c t e s sapidus, and Carc inus maenas) d e s t r o y l a r g e numbers o f o y s t e r C ( 7 S T t s o f f 1964). A l l s i z e s o f oys te r s a r e k i l l e d b u t sma l l s i z e s a r e a f f e c t e d most by o y s t e r d r i l l s , which bore th rough t h e s h e l l s w i t h a comb ina t ion o f chemical d i s s o l u t i o n o f t h e s h e l l and r a d u l a r rasp ing . Smal l o y s t e r s a r e p r e y e d on b y c r a b s and s t a r f i s h . The widespread b o r i n g

sponge C l i o n a weakens t h e s h e l l and t hus lowers qua1 i t y (Schlesselman 1955). S ~ a t a r e ~ r e v e d uDon bv t h e . "

f 1 atworm ' S t y1 ochus 'elli$t;;? (MacKenzie 1970; Ch r i stensen The bay anemone (Diadumene l euco lena ) consumed 0.6 t o 4;9 o y s t e r l a r v a e p e r m inu te i n t h e l a b o r a t o r y and a l s o feeds on l a r v a e i n t h e n a t u r a l environment ( S t e i n b e r g and K ~ n n e d y 1979). Over 100 bay anemones/m have been known t o occupy o y s t e r beds i n Chesapeake Bay (MacKenzie 1977). The sou the rn o y s t e r d r i 11 consumes 2.4 spa t /day under optimum c o n d i t i o n s ( G a r t o n and S t i c k l e 1 9 8 0 ) . I n a s tudy o f o y s t e r m o r t a l i t y i n Long I s - l a n d Sound, MacKenzi e (1981) es t ima ted t h a t s t a r f i s h i n f l i c t e d 25% m o r t a l i t y on spa t i n 5.5 months, mud crabs 12%, and o y s t e r d r i l l s 5%. F o r a d u l t o y s t e r s near Norwalk, New York, s t a r f i s h cause 3.2% o f t h e annual m o r t a l i t y , o y s t e r d r i 11s 0.2%, and s u f f o c a t i o n 0.2%. I n New Haven, Con- n e c t i c u t , s t a r f i s h had no impact , oys- t e r d r i l l s k i l l e d 0.5%/year, and su f - f o c a t i o n k i l l e d 2.9%/year. The o y s t e r d r i l l s a r e t h e p r i m a r y p reda to r s o f o y s t e r s i n Chesapeake Bay (L ippson 1973). I n t h e G u l f o f Mexico, o y s t e r s a r e preyed on by a v a r i e t y of o t h e r p r e d a t o r s (Cake 1983).

Ma jo r c o n p e t i t o r s of t h e o y s t e r f o r space on s u b s t r a t e i n c l u d e t h e s l i p p e r s h e l l s (Cre i d u l a spp.) and t h e j i n g l e s h e l l s -f- Anomia spp.) as we1 1 as barnac les (Ba l anus ebu rneus and Chthamalus f r a g w a n d o t h e r o y 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- Kenzie 1970; 1983). S h e l l s w i t h heavy f o u l i n g by barnac les have o n l y about 25% as many spa t as c l ean s h e l l s (Manning 1953). Heavy s e t s o f ba rnac les reduce t h e ha rd s u r f a c e a v a i l a b l e f o r o y s t e r s p a t and t h u s reduce o y s t e r s e t t l e m e n t ( I n g l e 1951); t h e r e f o r e o y s t e r spa t a r e l i m i t e d t o areas r e l a t i v e l y f r e e o f ba rnac les and bryozoans (Beaven 1955). The mussel B rach iodon tes exustus may a l s o conpete w i t h o y s t e r s ( O r t e g a 1981) . Young o y s t e r s may be smothered by exc re ta o f po l ychae te worms of t h e genus

Polydora, o r by exc re ta of a d u l t ovs te r s (S tenze l 1971). Blooms o f r ed t; de ( ~ o c h 1 od i n i um h e t e r o l obatum) a t c o n c e n t r a t i o n s 0 0 c e l l s /m l k i 11 ed o y s t e r l a r v a e (Ho and Zubkof f 1979). Compet i t i on by t h e s l i p p e r s h e l l s and barnacles may l i m i t numbers o f oys te r s i n Long I s 1 and Sound (MacKenzi e 1981; 1983). Tuni ca tes and e n c r u s t i n g sponges a r e a l s o major compet i to rs f o r space (D. S. Haven, pers. comm.).

ENVIRONMENTAL REQUIREMENTS

The American o y s t e r t y p i c a l l y l i v e s i n sha l low, we l l -m ixed es tua r - i e s , lagoons, and nearshore bays, and t o l e r a t e s w i d e l y f l u c t u a t i n g wate r temperatures , s a l i n i t i e s , and suspended s o l i d concent r a t i ons (Andrews 1979a). Because o f t h e t o l e r a n c e o f extreme f l u c t u a t i o n s i n env i ronmenta l c o n d i t i o n s , t h e env i r on - mental requ i rements o f o y s t e r s a r e d i f f i c u l t t o d e f i n e .

Temperature

D i f f e r e n c e s i n therma l r e q u i r e - ments o f oys te r s f r o m 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 t h a t races may be separated on t h e bas is of d i f f e r e n t temperature requ i rements (Ahmed 1975). Approximate spawning temperatures f o r t h r e e d i s t i n c t races were 16 OC f o r t h e n o r t h e r n race (New England), 20 OC f o r t h e m i d - A t l a n t i c race, and 25 O C f o r t h e Gulf o f Mexico race (S tauber 1950). Menzel (1955) found t h a t c i l i a r y a c t i v i t y con t inued a t 0 O C i n t h e New England oys te r s b u t ceased a t 6 O C i n o y s t e r s f r o m t h e m i d - A t l a n t i c . Andrews (1979a) s u g g e s t e d t h e r e a r e o t h e r r a c e s as w e l l , b u t gene t i c s t u d 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 e n c e o f p h y s i o l o g i c a l races (Bu r o k e r e t a1 . 1979). A l l o y s t e r s s t u d i e d by Buroker e t a l . (1979) were g e n e t i c a l l y i d e n t i c a l , except t hose from 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 of

s i mi 1 a r i t y between t h e American and t h e mangrove oys te r , which can suc- c e s s f u l l y h y b r i d i z e (Menzel 1968). Accord ing t o Groue and L e s t e r (1982) American oys te r s i n Laguna Madre, Texas, a r e g e n e t i c a l l y d i s t i n c t f r om f o u r o t h e r g u l f popu la t i ons . Measure- ment o f isozymes i n g e n e t i c s t ud ies , however, may n o t v a l i d a t e t hese races.

I n t h e m i d - A t l a n t i c coas ta l waters, oys te r s spawn when wate r temperatures a r e somewhat above 20 "C. Gonads do no t develop a t wa te r temperatures below 10 O C , and 16 O C i s needed f o r gonadal m a t u r a t i o n (Loosa- n o f f and Davis 1952). Exposure t o a 35 O C water temperature acce le ra ted gametogenes i s and spawning, b u t subsequent spawning i n t h e same season was p reven ted (Quick 1971). I n l a b o r a t o r y t e s t s , embryos developed norma l l y a t wa te r temperatures between 20' and 30 OC bu t abno rma l i t i e s inc reased p rog ress i v e l y when water temperatures d e c l i n e d t o 15 O C o r r o s e t o 35 O C

(MacInnes and Calabrese 1979). The percentage o f abnormal embryos inc reased f rom 2% a t 25 O C t o 12% a t 30 O C (Dupuy 1975 ) . The g r o w t h o f l a r v a e was impa i red by wate r temper- a t u r e s o f 30 O C o r more and even a b r i e f e x p o s u r e f o r 10 m i n a t 40 O C

r e t a r d e d growth (Hidu e t a l . 1974). I n c o n t r a s t , a temperature range o f 27 t o 32 O C i s optimum 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 of l a r v a e i n Long I s l a n d Sound (Davis and Cal abrese 1964).

A d u l t s t o l e r a t e wa te r tempera- t u r e s f r o m a l o w o f - 2 O C i n New England t o a h i g h o f 36 O C i n t h e Gu l f o f Mexico. At low t i d e , oys te r s may be exposed t o and s u r v i v e a i r temper- a tu res r ang ing f r o m we1 1 below f r e e z i n g t o above 49 OC ( G a l t s o f f 1964). High temperatu res sometimes i nc rease t h e m o r t a l i t y r a t e ; tempera- t u r e s above 35 O C f o r an e n t i r e t i d a l c y c l e may k i l l some o r a l l o y s t e r s ( T i nsman and Maurer 1974). The c r i t i - c a l therma l maximum f o r t h e American o y s t e r i s 48 O C (Henderson 1929).

Oysters can t o l e r a t e f r e e z i n g o f t h e i r t i s sues , and sometimes r e v i v e a f t e r thawing (Loosanof f 1965a).

Optimum water temperatures f o r c a r r y i n g o u t va r ious l i f e func t ions i n t h e a d u l t American o y s t e r a r e 20 t o 30 OC. Optimum temperatures f o r maximum pumping r a t e s were 20 t o 25 OC ( C o l l i e r 1951 ) o r a t 28 t o 32 OC ( L o o s a n o f f 1958) . Growth s t o p s i n waters w i t h temperatures below about 8 OC ( P r i c e e t a l . 1975). Oysters a t 2 t o 7 O C a r e i n a c t i v e . The t h r e s h o l d f o r f e e d i n g i s 3 OC (Haven and Mora l - es-Alamo 1966). Exposure t o unseasonably h i gh temperatures i n w i n t e r s t i m u l a t e s growth i f food i s 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 32 OC b u t t h e optimum i s about 26 OC ( G a l t s o f f 1964).

S a l i n i t y

Oysters p r e f e r waters o f r e l a t i v e l y h i g h s a l i n i t y . When s a l i n i t y i s above about 20 p p t , mar ine p reda to r s f l o u r i s h and des t roy l a r g e numbers of oys te rs . Oysters u s u a l l y l i v e i n b rack i sh waters o r i n areas o f u n s t a b l e s a l i n i t y t h a t a r e u n s u i t a b l e f o r mar ine p reda to rs . I n upper Chesapeake Bay, f o r example, spa t d e n s i t y was p o s i t i v e l y c o r r e l a t e d w i t h h i g h s a l i n i t y , whereas o y s t e r ha rves t was n e g a t i v e l y c o r r e l a t e d w i t h h i g h s a l i n i t y ( l l l anowicz e t a1 . 1980).

S a l i n i t i e s above 7 p p t a r e r e - q u i r e d f o r spawning (Loosanof f 1948). Embryos developed normal l y a t s a l i n i t i e s o f 16 t o 30 p p t (MacInnes and Calabrese 1979). Larvae t o l e r a t e d s a l i n i t i e s o f 3 t o 31 p p t ( C a r r i k e r 1951), bu t grow f a s t e s t and s u r v i ved best a t s a l i n i t i e s above 12 p p t (Davis and C a l a b r e s e 1964 ) . I n V i r g i n i a , s a l i n i t i e s o f 20 t o 35 p p t were requ i r e d f o r normal embryo development and t h e optimum was 28 p p t (Castagna and Chanley 1973). I n t h e l abo ra to r y , a lmost no embryos o f Long I s l a n d Sound oys te r s developed below 15 pp t ; t h e percentage p r o g r e s s i v e l y inc reased t o

a s a l i n i t y o f 22.5 p p t (Davis 1958). As s a l i n i t y inc reased f u r t h e r t o 35 p p t , abnormal i t i e s increased, and a1 1 d i e d above 40 p p t . D i f f e r e n c e s i n s a l i n i t y t o l e r a n c e o f l a r v a e a r e ex- p l a i n e d by t h e a c c l i m a t i o n o f t h e a d u l t s be fo re spawning. Larvae produced f r o m t h e spawning of Maryland oys te r s acc l imated t o t h e s a l i n i t y of Long I s l a n d Sound ( 2 6 p p t ) h a d t h e same s a l i n i t y t o l e r a n c e as l a r v a e from Long I s l a n d Sound oys te r s . Mary land o y s t e r larvae, however, were much more t o l e r a n t o f low s a l i n i t i e s if t h e pa ren t s were acc l imated t o 9 p p t wa te r ( s i m i l a r t o Chesapeake Bay). The l a r v a e f r o m p a r e n t s a d a p t e d t o l o w s a l i n i t y developed norma l l y a t 10 pp t , and most s u r v i v e d a t 7.5 pp t . Development stopped a t 22.5 pp t , which would be t h e optimum s a l i n i t y i f t h e paren ts had been h e l d a t h i g h e r s a l i n i t i e s .

Most l a r v a e i n a New Jersey es- t u a r y 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 p p t ( C a r r i k e r 1951 ) . Larvae o f V i r g i n i a oys te r s of paren ts i n h i g h s a l i n i t y wa te r d i d n o t metamorphose below 17.5 p p t (Castagna and Chanley 1973), a f i n d i n g obv ious l y n o t a p p l i c a b l e t o popu la t i ons 1 i v i n g i n low s a l i n e waters. Optimum s a l i n i - t i e s f o r t h e growth o f spa t i n lower Chesapeake Bay were 15 t o 22 p p t (Chanley 1957) and i n Long I s l a n d Sound, 17.5 t o 22.5 p p t (Davis 1958). Oysters i n Chesapeake Bay d i d n o t grow a t s a l i n i t i e s below 5 p p t (Abbe 1982).

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 r a n g e o f 5 t o 3 2 p p t . O u t s i d e of t h i s r a n g e o f s a l i n i t i e s t h e y d i s - con t i nue f eed ing and reproducing. The optimum s a l i n i t y range i n Long I s l a n d Sound i s 10 t o 28 p p t (Loosanof f 1965a) and i n Delaware Bay, 14 t o 28 p p t (Maurer and W a t l i n g 1973). Loosa- n o f f (1965b) found t h a t many oys te r s s u r v i v e 3 p p t f o r 30 days. Large numbers, however, d i e d u r i n g p ro longed f r eshwa te r i n f l o w f r om t h e James R i ve r , V i r g i n i a (Andrews e t a l . 1959; Andrews 1973). S i m i l a r observa t ions were made i n Mob i l e Bay, Alabama (May

1972), and i n t h e Santee River, South Caro l i na (Bur re l 1 1977). S a l i n i t i e s du r ing h igh f reshwater i n f l o w were below 2 ppt i n t h e Santee River. Many oysters d ied i n t h e Beaufor t I n l e t , North Carol ina, a f t e r exposure t o a s a l i n i t y near 5 ppt f o r about a month (We1 1s 1961). Oysters i n Louisiana d ied a f t e r 14 days a t 6 pp t (Anderson and Anderson 1975). I n Delaware Bay, oysters surv ived s a l i n i t i e s as low as 2 p p t (Maurer e t a l . 1971). The l e n g t h o f t i m e o y s t e r s s u r v i v e low s a l i n i t i e s ev iden t l y depends on t h e abruptness o f t h e changes i n s a l i n i t y .

Low s a l i n i t i e s i n h i b i t gonadal maturat ion i n oysters i n Chesapeake Bay ( B u t l e r 1949) and Long I s l a n d Sound (Loosanoff 1953). Reproductive f a i l u r e may be a d i r e c t e f f e c t o f sa- l i n i t y o r might be caused by inade- quate feeding a t low s a l i n i t y .

Substrate and Current

The p re fe r red h a b i t a t s i n shal low e s t u a r i n e wa te rs a r e mud f l a t s and o f f sho re bars (Hidu 1968), and oys ter ree fs (Bahr and Lani e r 1981). Maximum dens i ty o f spat i s on ho r i zon ta l surfaces (Clime 1976).

Oysters grow equa l l y w e l l on s h e l l s , rocky bot toms, o r on t h i c k mud, capable o f suppor t ing t h e oys te rs ' weight. So f t mddy substrates may be improved by adding clam o r oys te r she l l s . Oyster s h e l l s from ruddy substrates a re more s lender than those f rom hard substrates (Ga l t so f f 1964). I n Delaware Bay mar i cu l tu re s i t e s , oysters p r e f e r r e d t o se t on t h e bottom r a t h e r than on panels suspended i n t h e water column, and p r e f e r r e d sub t ida l waters (Hidu 1978).

Currents a r e p a r t i c u l a r l y important t o t h e la rvae and adu l ts o f t h e American oyster . Larvae a re t ranspor ted by currents. They p o s i t i o n themselves i n t h e ebb and f low of t i d a l currents t o remain i n estuar ies. Excessive currents,

however, may prevent set t lement (Cake 1983). Since t h e volume o f water i m - mediate ly above an oys ter bed must be completely f l ushed about 72 times every 24 h r f o r maximum feeding, oys- t e r s requ i re cur rents (Ga l t so f f 1964). T i d a l f lows o f 156 t o 260 cm/sec o r h igher are needed f o r optimum growth i n M i s s i s s i p p i (Vea l e t a l . 1972). Currents over oys te r bars i n Beaufor t I n l e t and t h e Newport R ive r estuary i n North Caro l ina were 11 t o 66 cm/sec (Wells 1961). Currents o f 150 t o 600 cm/sec were measured above oys te r bars i n Delaware Bay (Hidu and Haskin 1971), and 180 cm/sec i n M i l f o r d Harbor, Connecticut (Prytherch 1929). Turbulent currents t h a t c a r r y sand and pebbles, however, can damage s h e l l s by erod ing s h e l l sur faces (Gal tso f f 1964). A v e l o c i t y o f 150 cm/sec caused unattached oysters t o tumble a long t h e bottom o f Long I s l a n d Sound (MacKenzie 1981). I n Delaware Bay, oyster abundance was greates t i n areas o f scour where cur rent kept t h e beds f r e e o f sediments (Keck e t a l . 1973). Oysters d ied i n one week i f covered w i t h sediment a t a water temperature o f 20 O C , and i n 2 days i f t h e water temperature was 25 OC (Dunnington 1968). Currents are a l so necessary f o r removal o f pseudofeces and feces (Lund 1957).

Oxygen

I n one study, t h e hour l y oxygen consumption was 39 ml/kg f o r a whole animal i nc lud ing t h e s h e l l o r 303 m l / k g of wet t i s s u e (Hammen 1969). Oxygen consumpti on increases w i t h increas ing temperature; QI0 values ( t h e f a c t o r by which a reac t i on v e l o c i t y i s increased by an increase i n temperature o f 10 OC) ranged from 1.2 t o 2.3 f o r g i l l t i s s u e and 2.7 t o 4.2 f o r mantle t i s s u e (Bass 1977).

The r a t e o f oxygen consumption by oysters increases as temperature increases and s a l i n i t i e s decrease (F igure 3). Oysters exposed t o prolonged per iods o f low s a l i n i t i e s closed t h e i r s h e l l s and d ied o f anoxia

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

i n t h e James R i v e r and Rappahannock R i v e r e s t u a r i e s (Andrews 1982b). Oys- t e r s a r e f a c u l t a t i v e anaerobes and a r e a b l e t o s u r v i v e d a i l y exposure t o low oxygen. They a l s o a r e known t 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 a f t e r spawning ( G a l t s o f f 1964). Oxygen consumption i s ze ro when t h e va lves a r e c l osed (Hamnen 1969). I n a s t udy i n Delaware Bay, oxygen concen t ra t i ons over o y s t e r r e e f s ranged f r om 1 t o 12 mg/l (Maurer e t a l . 1971). The d e c l i n e i n o y s t e r h a r v e s t i n Chesa- peake Bay i n r ecen t years may be caused by decreased concen t ra t i ons o f oxygen, a l though more e s t a b l i s h e d f a c t o r s i n c l u d e t h e outbreak of MSX d isease i n 1981-1983, poor spa t s e t

f o r ove r a decade, and h i g h ha r ves t p ressure .

T u r b i d i t y and Sed imenta t ion

Oys te rs t o l e r a t e wa te r w i t h l a r g e amounts o f suspended s o l i d s , b u t t h e pumpi ng r a t e decreases w i t h i n c r e a s i n g concen t ra t i ons o f suspended s o l i d s . Pumping i s reduced 70% t o 85% over t h e r a n g e 0 t o 1 g / l , d e p e n d i n g on t h e n a t u r e o f t h e suspended sediment (Loosanof f and Tommers 1948). I n t h e l a b o r a t o r y t h e growth o f l a r v a e was reduced a t concent r a t i ons o f p a r t i c u l a t e s above 0.75 g / l (Dav is and Hidu 1969). I n n a t u r a l environments, o y s t e r s appa ren t l y develop and grow b e t t e r i n waters w i t h more suspended s o l i d s i n o y s t e r beds t han i n waters w i t h 1 ess suspended p a r t i c u l a t e s (Rhoads 1973). Storms and h u r r i c a n e s may d e s t r o y o y s t e r r e e f s by cove r i ng them w i t h sediment.

A c i d i t y

O y s t e r embryos deve l op normal l y w i t h i n a pH range o f 6.8 t o 8.8 and develop abnorma l l y a t a pH above 9.0 o r below 6.5 (Calabrese and Davis 1966; Calabrese 1972). Larvae t o l e r a t e t h e same pH range as embryos b u t growth i s f a s t e s t a t a pH o f 8.2 t o 8.5.

LITERATURE CITED

Abbe, G.R. 1982. Growth, m o r t a l i t y , and copper-n ickel accumulat ion by . . oys te r s (Crassostrea v i r g i n i c a ) a t t h e Moraantown steam e l e c t r i c s t a t i o n o n t h e Potomac R iver , Maryland. J. S h e l l f i s h Res. 2 (1 ) : 3-13.

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

A l f o r d , J.J. 1975. The Chesapeake o y s t e r f i s h e r y . Ann. Soc. Am. Geogr. 65:229-239.

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 ro leum hydrocarbons on osmot ic and c h l o r i d e regu la - t i o n o f t h e American o y s t e r K- sos t rea v i r i n i c a . Phys io l . Zool . TqT732+

Andrews, J.D. 1949. The 1947 oys te r s t r i k e i n t h e James R iver . Proc. N a t l . Shel l f i s h . Assoc. 39:61-66.

Andrews, J.D. 1951. Seasonal pa t t e rns o f o y s t e r s e t t i n g i n t h e James R i v e r and Chesapeake Bay. Ecology 32: 752-758.

Andrews, J.D. 1955. S e t t i n g of oys te rs i n V i r g i n i a . Proc. Na t l . Shel l f ish. Assoc. 45: 38-46.

Andrews, J .D. 1968. Oys te r m o r t a l i t y s t u d i e s i n V i r g i n i a : V I I . Review of e ~ i z o o t i o l o a v and o r i a i n o f ~ i n c h i n i a n e l s G i . P r o c . " ~ a t l . Shel l f ish. Assoc. 58:23-36.

Andrews, J.D. 1973. E f f e c t s o f t r o p - i c a l s torm Agnes on epi fauna i n - ver tebra tes i n V i r g i n i a estua- r i e s . Chesapeake Sc i . 14:223-234.

Andrews , J .D. 1979a. Pel ecypoda: Os t re idae . Pages 291-341 i n A.C. Giese and J.S. Pearse, eds. Reproduct ion o f marine i n v e r t e - b ra tes . Vol . V. Mo l luscs : Pelecy- pods and l e s s e r classes. Academic Press, New York.

Andrews , J .D. 1979b. Oys te r diseases i n Chesapeake Bay. Mar. F ish . Rev. 41(1):45-53.

Andrews, J .D. 1982a. Ep i zoo t i o l ogy of l a t e sumner and f a l l i n f e c t i o n s o f oys te rs by Haplospor id ium ne l son i , and comparison t o annual 1 i f e c y c l e o f Haplospor id ium c o s t a l i s , a t y p i c a l haplospor idan. J. S h e l l f i s h Res. 2 (1 ) : 15-23.

Andrews, J.D. 1982b. Anaerobic m o r t a l i t i e s o f oys te rs i n V i r g i n i a caused by low s a l i n i t i e s . J. S h e l l f i s h Res. 2 (2 ) : 127-132.

Andrews, J.D., and J.L. McHugh. 1957. The s u r v i v a l and growth o f South C a r o l i n a seed oys te rs i n V i r g i n i a waters. Proc. Na t l . S h e l l f i s h . Assoc. 47: 3-17.

Andrews, J.D., D. Haven, and D.B. Quayle. 1959. Freshwater k i l l o f oys te rs (Crassostrea v i r g i n i c a )

i n James R i v e r , V i r g i n i a , 1958. Proc. Na t l . S h e l l f i s h . Assoc. 49: 29-49.

Bahr, L.M., J r . 1976. Ene rge t i c aspects 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 and , 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 coas t : a community p r o f i l e . U.S. F i s h W i l d l . Serv., B i o l . Serv., FWS/OBS-81/15 105 pp.

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 consumption o f t i s s u e s i n t h e Amer- i c a n o y s t e r (Crassos t rea v i r g i n - i c a ) . Comp. Biochem. Phys io l . - 58B:125-130.

Beaven, G.F. 1955. Var ious aspects o f o y s t e r s e t t i n g i n Maryland. Proc. N a t l . S h e l l f i s h . Assoc. 45: 29-37.

Brown, C., and G. Roland. 1984. C h a r a c t e r i z a t i o n o f exo tox i n produced b.y a s h e l l f i s h - ba thogen ic v-ibrio sp. J. F i s h Dis . 7 (2 ) : 117-126.

Burke, R.D. 1953. The i n d u c t i o n o f metamorphosis o f mar ine i n v e r - t e b r a t e 1 arvae: s t i m u l u s and response . Can. J. Z o o l . 6 1 ( 8 ) : 1701-1719.

Buroker, N .E., W .K. Hershberger , and K.K. Chew. 1979. Popu la t i on gene- t i c s o f t h e f a m i l y Os t re i dae 11. 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 Crassost rea and Saccostrea. Mar. B i o l . ( B e r l .) 54: 171-184.

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 oys te r s and hard clams associ - 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 of 1975. Proc. N a t l . Shel 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 Hole) 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 r o c . - ~ a t l . S h e l l f i s h . Assoc. 43:188-191.

Cake, E.W., J r . 1983. H a b i t a t s u i t a b i l i t y index models: Gu l f o f Mexico American oys te rs . U.S. F i s h W i l d l . Serv. FWS/OBS-82/20/57. 37 pp.

Calabrese, A. 1972. How some p o l l u t - ants a f f e c t embryos and l a r v a e o f Amer i can o y s t e r and h a r d s h e l l clam. Mar. F ish . Rev. 34(11-12): 66-77.

Calabrese, A., and H.C. Davis. 1966. The pH t o l e r a n c e o f embryos and 1 arvae and B i o l . 113(3):

o f Mercenar i a mer~cenar i a Crassost rea v i r g i n ica.

B u l l . (Woods Ho le )

C a r r i k e r , M.R. 1951. E c o l o g i c a 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 o y s t e r l a r vae i n New Jersey es tu - a r i e s . Ecol . Monogr. 21(1) : 19-38.

C a r r i k e r , M.R. 1959. The r o l e o f p h y s i c a l and b i o l o g i c a l f a c t o r s i n t h e c u l t u r e of Crassos t rea and Mercenar ia i n a s a l t wa te r pond. Ecol . Monogr. 29(3) : 219-266.

C a r r i k e r , M.R., and R.E. Palmer. 1979. U l t r a s t r u c t u r a l morphogenesis o f prodissoconch and e a r l y d i sso - conch va lves o f t h e o y s t e r ICras- " *-

s o s t r e a v i r g i n i c a ) . Proc. N a t l . Shel l f i sh . Assoc. 69: 103-128.

C a r r i k e r , M.R., C.P. Swann, and J.W. Ewart. 1982. An e x p l o r a t o r y s tudy w i t h t h e p r o t o n microprobe o f t h e on togene t i c d i s t r i b u t i o n o f 16 elements i n t h e she1 1 o f l i v i n g oys te r s (Crassost rea v i r i n i c a ) ; Mar. B i o l . (Ber l . ) 69:23&%6-

Castagna, M. and P. Chan ley . 1973. Sal i n i t y t o l e r a n c e of some marine b i v a l v e s f rom i nsho re and e s t u a r i n e environments i n V i r g i n i a w a t e r s of t h e w e s t e r n mi d-At1 a n t i c coast. Ma1 acol og ia 12(1):47-96.

Chanley, P.E. 1957. S u r v i v a l o f some j u v e n i l e b i va l ves i n water o f low s a l i n i t y . Proc. N a t l . S h e l l f i s h . Assoc. 48:52-65.

Chr is tensen, D.J. 1973. Prey p r e f e r - ence o f Sty lochus e l l i p t i c u s i n Chesapeake Bay. Proc. N a t l . she1 l f i s h . ~ s s o c . 63:35-58.

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 ovs te rs Ostrea e d u l i s L. -- and ~ ~ a s s ' o s t r e a v i r g i n i c a Gmel i n . Master 's Thesis, U n i v e r s i t y o f Maine a t Orono. 94 pp.

C o l l i e r , A. 1951. A s tudy o f t h e re - sponse o f oys te rs t o temperature and some long-range eco log i ca l i n t e p r e t a t i o n s . Proc. Na t l . S h e l r f ish. Assoc. 42: 13-38.

C r i sp , D.J. 1967. Chemical f ac to r s i nducing se t t lement i n Crassos- t r e a v i r i n i c a (Gmelin). J . Anim. m . 3 & 3 9 - 3 3 5 .

Dame, R.F., J r . 1971. The eco log i ca 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 v s t e r Crassostrea v i rgi n i c a ( ~ m e l i i ) . Ph .D. Thesis. U n i v e r s i t y o f South Caro l ina , co1umbia.- 81 pp.

Dame, R.F. 1976. Energy f l o w i n an i n t e r t i d a l o y s t e r popu la t ion . Estuar . Coasta l Mar. Sc i . 4 (3 ) : 243-253.

Davis, H.C. 1953. On food and f eed ing o f l a r v a e o f t h e American oys te r , C . v i r i n i c a . B i o l . B u l l . (Woods iTol e h : 334-350.

Davis, H.C. 1958. S u r v i v a l and growth of clam and o y s t e r l a r v a e a t

d i f f e r e n t s a l i n i t i e s . B i o l . B u l l . (Woods Ho le ) 114(3):296-307.

Davis, H.C., and A. Calabrese. 1964. Combined e f f e c t s o f temperature and s a 1 i n i t . y on deve lopment o f eggs and o f l a r v a e o f - M. mercenar ia and C. v i r g i n i c a . U.S. F i sh W i l d l . Serv. F ish. 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.

Davis, H.C., and H. Hidu. 1969. E f f e c t s o f t u r b i d i t y -p roduc ing substances i n sea water on eggs and l a r v a e o f t h r e e genera o f b i v a l v e mol lusks. V e l i g e r 11: 316-323.

D r i nnan, R .E., and W.B. S t a l lwor thy. 1979. Oyster l a r v a l popu la t ions and assessment of s p a t f a l l , 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): 1-13.

Dunni ngton, E.A., J r . 1968. S u r v i v a l t i m e o f oys te rs a f t e r b u r i a l a t var ious temperatures. Proc. N a t l . S h e l l f i s h . Assoc. 58:lOl-103.

Dupuy, J.L. 1975. Some p h y s i c a l and n u t r i t i o n a l f ac to r s which a f f e c t t h e g row th and s e t t i n q o f t h e l a r v a e of t h e oys te r , ~ r a s s o s t r e a v i r g i n i c a i n t h e l abo ra to ry . Pages 195-202 i n F.J. Ve rnbe rq ed .- Phys i 01 ogTca1 ecology o f e s t u a r i n e organisms. U n i v e r s i t y o f South C a r o l i n a Press ,Columbia.

Engle, J.B. 1956. Ten years o f s tudy on o y s t e r s e t t i n g i n a seed area i n u p p e r Chesapeake Bay. Proc . N a t l . S h e l l f i s h . Assoc. 46:88-99.

G a l t s o f f , P.S. 1964. The American oys te r Crassostrea v i r g i n i c a IGmelin). U.S. F i s h W i l d l . Serv. f i s h . ~ " 1 1 . 64: 1-480.

Garton, D., and W.B. S t i ck le . 1980. E f f e c t s o f s a l i n i t y and tempera- t u r e on t h e p r e d a t i o n r a t e o f Thais haemastoma on Crassostrea v i r i n i c a spat. B i o l . B u l l . &le) 158: 49-57.

G i l lmor , R.B. 1982. Assessment o f i n t e r t i d a l growth and capac i ty adaptat ions i n suspension-feeding b iva lves . Mar. B i o l . (Ber l .) 68(3) : 277-286.

Groue, K.J., and L.J. Lester . 1982. A morphological and genet ic analy- s i s o f geographic v a r i a t i o n among oys ters i n t h e Gulf of Mexico. Vel i ger 24 (4 ) : 331-335.

Gu i l l a rd , R.R. 1957. Some f a c t o r s i n t h e use o f nannoplankton cu l tu res as food f o r l a r v a l and j u v e n i l e b ivalves. Proc. Na t l . She1 l f i s h . Assoc. 48: 134-142.

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

Hamrnen. C.S. 1969. Metabolism o f t h e oys te r Crassostrea v i r g i n i ca. Am. Zoo1 . 9(2): 309-318.

Haskin, H.H. 1964. The d i s t r i b u t i o n o f oys te r larvae. Proc. o f a symposium on experimental marine eco l - ogy. Occas. Pap. 2, Grad. School Oceanogr., Uni v. R.I.:76-80.

Haven, D. 1962. Seasonal c y c l e o f c o n d i t i o n index o f oys ters i n t h e York and Rappahannock Rivers. Proc. Nat l . S h e l l f i s h Assoc. 51: 42-66.

Haven, D .S., and R. Moral es-A1 amo. 1966. Aspects o f biodeposi ti on by oysters and o ther i nve r teb ra te f i l t e r feeders. Limn01 . Oceanogr. 11(4):487-498.

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 from suspension by t h e American oys ter Crassostrea v i rg in i ca .

B i o l . B u l l . (Woods Hole) 139(2): 240-264.

Hayes, P.F., and R.W. Menzel. 1981. The reproduct ive c.yc1e o f e a r l y s e t t i n g ~ r a s s o s t r e a v i r g i n i c a IGrnel i n ) i n t h e nor thern Gul f of ~ e x i c o , ' and i t s imp1 i c a t i o n s f o r popu la t i on recrui tment. B i o l . Bu 1 1. (Woods Hole) 160:80-88.

Henderson, J .T. 1929. Letha l temperatu res o f Lame1 1 i branchi ata. Con- t r i b . Can. B i o l . 4(25):397-411.

Hidu. H. 1968. Inshore set t lement of Crassostrea v i r g i n i c a i n Delaware Bav. Proc. Nat l . She l l f i sh . ~ s s o c . 58:4 (Abstr.)

Hidu. H. 1969. Gregarious s e t t i n g i n - t h e American oys te r ~rassos- t rea v i r i n i c a ~ m e l i n . Chesapeake Sci. .+92.

Hidu, H. 1978. S e t t i n g o f es tua r ine inver tebra tes i n Delaware Bay, New Jersey, r e l a t e d t o i n t e r - t i d a l - s u b t i d a l gradients. I n t . Rev. Gesamten Hydrobiol. 63:637- 662.

Hidu, H., and H.H. Haskin. 1971. S e t t i n g o f t h e American o y s t e r r e l a t e d t o envi ronmental fac tors and 1 a rva l behavior. Proc. Na t l . S h e l l f i s h . Assoc. 61:35-50.

Hidu, H., and H.H. Haskin. 1978. Swimminq speeds o f 0-yster la rvae ~ r a s s o s t r e a v i r g i n i c i i n d i f f e r - ent s a l i n i t i e s and tem~era tu res . Es tuar ies l ( 4 ) : 252-255.

Hidu, H., W.H. Roosenburg, K.G. Dro- beck, A.J. McErlean, and J.A. M i - hurskv. 1974. Thermal to le rance o f oys ter l a rvae Crassostrea c- g i n i c a Gmelin, as r e l a t e d t o pow- e r p l a n t o ~ e r a t i o n . Proc. Nat l .

Higgins, P.J. 1980. E f f e c t s o f food a v a i l a b i l i t y on t h e valve movements and feed ing behavior of

j u ven i 1e Crassos t rea v i r g i n i c a (Gmelin). I. Valve movements and p e r i o d i c a c t i v i t y . J. Exp. Mar. B i o l . Ecol . 45: 229-244.

Ho, M.S., and P.L. Z u b k o f f . 1979. The e f f e c t s o f a Cochlodi nium he te ro laba tum bloom on t h e s u r v i v a l and c a l c i u m u p t a k e by l a r v a e o f t h e Amer i can o y s t e r . Crassos t rea v i r g i n ica . - pages 409-413 i n D.L. T a v l o r and H.H. - S e l i g e r , eds. ~ o x i c d i n o f l a g e l - l a t e blooms. E l s e v i e r , New York.

Hopkins, S.H,, J.G. Mackin, and R.W. Menzel. 1954. The annual c y c l e o f reproduc t i on, growth, and f a t t e n i n g i n Lou i s i ana oysters . Proc. Na t l . S h e l l f i s h . Assoc. 44: 39-50.

I n g l e s , R.M. 1951. Spawning and s e t t i n g o f oys te r s i n r e l a t i o n t o seasonal env i ronmenta l changes. B u l l . Mar. Sc i . Gu l f Caribb. 1: 111-135.

I n g l e s , R.M., and C.E. Dawson, Jr. 1952. Growth o f t h e Amer i can o y s t e r Crassost rea v i r g i n i c a (Gmel in) i n F l o r i d a waters. ~ u l l . Mar. Sc i . ~ u l f . ~ a r i b b . 2: 393-404.

Kaufman, Z.S. 1978. Dependence of t h e t i m e o f gamete ma tu ra t i on and spawning on t h e env i ronmental temperature i n V i r g i n i a o y s t e r Crassos t rea v i r i n i c a . Hydrob io l . TTqTJm - - +

Keck, R., D. Maurer, and L. Watl i n g . 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 . Hyd rob io l og ia 42(4 ) : 369-379.

Kennedy, V.S. 1980. Compar ison o f r ecen t and pas t p a t t e r n s of o y s t e r se t t l emen t and seasonal f o u l i n g i n Broad Creek and Tred Avon R iver , Maryland. Proc. Na t l . S h e l l f i s h . Assoc. 70: 36-46.

Kennedy, V.S., and L.B. Krantz . 1982. Comparat ive gametogenes i s and spawning p a t t e r n s o f t h e o y s t e r Crassos t rea v i r g i n i c a (Gmelin) i n c e n t r a l Chesapeake Bay. J. Shel l f i s h Res. 2 (2 ) : 133-140.

Kor r inga , P. 1976. Farming t h e cupped oys te r s o f 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.

Kran tz , G.E., and D.W. M e r i t t . 1977. An ana l ys i s o f t r ends i n oys te r spa t s e t i n t h e Mary land p o r t i o n o f Chesapeake Bay. P roc . N a t l . S h e l l f i s h . Assoc. 67: 53-59.

Krantz, G.E., and J.F. Chamberlin. 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 spat . Proc. N a t l . S h e l l f i s h . Assoc. 68:38-41.

Krantz , G.E., L.R. Buchanan, C.A. F a r l e y , and H.A. Car r . 1972. M i n c h i n i a ne l son i i n oys te rs f r o m Massachusetts waters. Proc. Nat 1. S h e l l f i s h . Assoc. 62:83-85.

Kunkle, D.E. 1957. The v e r t i c a l d i s t r i b u t i o n o f o y s t e r l a r v a e i n Delaware Bay. Proc. Nat 1. Shel 1 - f i s h Assoc. 48: 90-91.

Langefoss, C.M., and D. Maurer. 1975. Energy p a r t i t i o n i n g i n t h e Ameri- can oys te r , Crassos t rea v i r g i n i ca (Gmelin). Proc. N a t l . S h e l l f i s h . Assoc. 65: 20-25.

Lawrence, D.R., and G.I. Sco t t . 1982. The de te rm ina t i on and use o f c o n d i t i o n i ndex o f oys te rs . Es tua r i es 5 (1 ) : 23-27.

Lippson, A.J. 1973. The Chesapeake Bay i n M a r y l a n d . An a t l a s o f n a t u r a l resources. Johns Hopk i n s Press, Ba l t imore . 55 pp.

Loosanof f , V.L. 1932. Observat ions on p ropagat ion of oys te r s i n James and Corrotoman R i v e r s and t h e seas ide o f V i r g i n i a . V i r g i n i a

Commission o f F i she r i es , Newport News. 46 pp.

Loosanoff , V.L. 1948. Gonadal devel - opment and spawn ing 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 . Anat*l:705. (Abs t r . )

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

Loosanoff , V.L. 1958. Some aspects o f behav io r o f oys te rs a t d i f f e r e n t temperatures. B i o l . B u l l . (Woods Hole) 114(1):57-70.

Loosanoff , V.L. 1965a. The American o r eas te rn oys te r . U.S. F i s h W i l d l . Serv. C i r c . 205. 36 pp.

Loosanof f , V.L. 1965b. Gonad development and d i s c h a r g e of spawn i n oys te rs o f Long I s l a n d Sound. B i o l . B u l l . (Woods Hole) 129(3): 546-561.

Loosanoff , V.L. 1966. Time and i n t e n s i t y o f s e t t i n g o f t h e oys te r , Crassostrea v i r g i n i c a , i n Long I s l a n d Sound. B i o l . B u l l . (Woods Ho le ) 130(2): 211-227.

Loosanoff , V.L. 1969. Ma tu ra t i on o f gonads o f oys te rs , Crassostrea v i r g i n ica, o f d i f f e r e n t geograph- i c a l areas sub jec ted t o r e l a t i v e - l y 1 ow temperatures. Vel i ger 11 (3 ) : 153-163.

Loosanoff , V.L., H.C. Davis. 1952. Temperature requ i rements f o r m a t u r a t i o n of gonads of no r the rn oys te rs . B i o l . h u l l . (Woods Hole) 103 ( 1 ) : 80-96.

Loosanoff , V.L., and J.B. Engle. 1940. Spawning and s e t t i n g o f oys te rs i n Long I s l and Sound i n 1937, and d i scus ion o f t h e method f o r p r e - d i c t i n g t h e i n t e n s i t y and t i m e o f oys te r s e t t i n g . B u l l . U.S. Bur. F ish . 49:217-255.

Loosanoff , V.L., and C.A. Nomejko. 1946. Feeding o f oys te rs i n r e l a t i o n t o t i d a l stages and t o p e r i o d s o f 1 i g h t and darkness . B i o l . B u l l . (Woods Hole) 90(3) : 244-264.

Loosanof f , V.L., and C .A. Nomejko. 1949. Growth of oysters, 0. v i r g i n i c a , d u r i n g d i f f e r e n t months. B i o l . B u l l . (Woods Hole) 97 ( 1 ) : 82-94.

Loosanoff , V.L., and C .A. Nomejko, 1951. Spawning and s e t t i n g o f t h e American oys te r , 2. v i r g i n i c a i n r e l a t i o n t o l u n a r phases. Ecology 32(1): 223-234.

Loosanoff , V.L., and F.D. Tommers. 1948. E f f e c t o f suspended s i l t and o t h e r substances on r a t e of f e e d i n g o f oysters. Science 107: 69-70.

Losee, E. 1979. R e l a t i o n s h i p between l a r v a l and spa t 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 2 3 - l r $ L - Aquacul ture 16(2) .

Lund, E.J. 1957. S e l f - s i l t i n g , sur - v i v a l o f t h e o y s t e r as a c l o s e d system, and reduc ing t e n d e n c i e s o f t h e environment of t h e oys te r . Publ. I n s t . Mar. Sc i . Univ. Tex. 4(2):313-319.

Lutz, R.A., H. Hidu, and K.G. Drobeck. 1970. Acute temperature inc rease as a s t imu lus t o s e t t i n g i n t h e Ameri can o y s t e r Crassost rea e- g in ica . Proc. Na t l . S h e l l f i s h . Assoc. 60: 68-71.

Lutz, R., J. Goodsel l , M. Casatagna, S. Chapman, C. Newel l , H. Hidu, R. Mann, D. Jab lonsk i , V. K e n - nedy, S. S i d a l l , R. Goldberg, H. Bea t t i e , C. Falmagne, A. Chest- nu t , and A. Patr idge. 1982. Pre- 1 im inary observat ions on t h e use fu lness o f h inge s t r u c t u r e s f o r i d e n t i f i c a t i o n o f b i v a l v e la rvae . J. S h e l l f i s h Res. 2 ( 1 ) : 65-70.

MacInnes, J.R., and A. Calabrese. 1979. Combined e f f e c t s o f s a l i n i t y , temperature, and copper on embryos and e a r l y l a r v a e o f t h e American oys te r , Crassostrea v i r g i n i c a . Arch. Envi ron. Contam. Toxi c o l . 8: 553-562.

MacKenzie, C.L., J r . 1970. Causes o f o y s t e r spa t m o r t a l i t y , cond i t i ons 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 . Shel 1 - f. ish. Assoc. 60: 59-67.

MacKenzie, C.L., J r . 1977, Sea anemone p r e d a t i o n on l a r v a l oys te rs i n Chesapeake Bay (Maryl and). Proc. N a t l . S h e l l f i s h . Assoc. 67: 113-117.

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 g i n i c a i n Long I s l a n d Sound. Aquacu l tu re 22(3): 229-268.

MacKenzie, C.L., J r . 1983. To inc rease o y s t e r p roduc t i on i n t h e eas te rn U n i t e d States. Mar. F ish . Rev. 45(3): 1-22.

Manning, J.H. 1953. S e t t i n g of o y s t e r l a r v a e and s u r v i v a l o f s p a t i n t h e St. Mary's R iver , Maryland, i n r e l a t i o n t o f o u l i n g of c u l t c h . Proc. N a t l . Shel l f i s h . Assoc. 43: 74-78,

Manning, J.H., and H.H. Whaley. 1955. D i s t r i b u t i o n o f o y s t e r l a r v a e and spa t I n r e l a t i o n t o some envi ronmenta l f a c t o r i n a t i d a l estuary. Proc. Na t l . S h e l l f i s h Assoc. 45: 56-65.

Manz i , J.J., and V.G. B u r r e l l , J r . 1977. A comparison o f qrowth and

qrowth 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 ca (Gmel i n) i n South C a r o l i n a s a l t marsh impoundments. Aquacul ture 12: 293- 310.

Marsha l l , N. 1959. Oys te r s e t o b t a i n e d i n t h e N i a n t i c R i v e r , Connect icut , on c u l t c h buoyed near t h e surface. Ecology 40(2):298.

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 . Con t r i b . No. 2528. 52 pp.

Maurer, D., L. Wat l ing, and R. Keck. 1971. The Delaware o y s t e r i ndus t r y : a r e a l i t y ? Trans. Amer. F ish . Soc. 100(1):100-111.

Maurer, D., and L. Wat l ing . 1973. Studies on t h e o y s t e r community i n Delaware: t h e e f f e c t s o f t h e e s t u a r i ne env i ronment on t h e assoc ia ted fauna. I n t . Rev. Gesamten Hydrob io l . 58(2): 161- 201.

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. N a t l . S h e l l f i s h . Assoc. 62:67-71.

Menzel, R.W. 1955. Some phases of t h e b i o l o g y of Ostrea e q u e s t r i s and a c o m ~ a r i s o n w i t h Crassostrea v i r- - - - - . -~ .

gin;ca (Gmelin). Publ. I n s t . Mar. Sc i . Univ. Tex. 4: 69-153.

Menzel , R .W. 1968. Cytotaxonomy o f species o f clams (Mercenar ia) and oys te rs (Crassostrea) . Symp. Mo l lusca Mar. B i o l . Assoc. I n d i a 1: 53-58.

s u r v i v a l of' s u b t i d a l ~ k a s s o s t r e a v i r g i n i c a i n South Ca ro l i na s a l t M e r r i l l , A.S., and K.J. Boss. 1966, marsh impoundments. Proc. N a t l . Ben th i c ecology and faunal change

Shel l f i s h . Assoc. 67: 120-121. r e l a t i n g t o oys te rs from a deep bas in i n t h e lower Patuxent

Manzi, J.J., V.G. B u r r e l l , and W.Z. R i ve r , Maryl and. Proc. N a t l , C a r l s o n . 1977. A compar i son o f S h e l l f i s h . Assoc. 56:81-87.

Morse, D.C. 1945. Some observations on t h e food and feeding o f oysters i n Chesapeake Bay. Proc. Nat l . S h e l l f i s h . Assoc. 35:3.

Nelson, T.C. 1928. R e l a t i o n o f spawn- i n g o f t h e oys te r t o temperature. Ecology 9: 145-154.

Newkirk, G.F., L.E. Haley, D.L. Waugh, and R. Doyle. 1977. Genetics o f l a r v a e and s ~ a t ~ r o w t h r a t e i n t h e oys ter ~ r a s s o s t r e a v i r i n i c a . Mar. B i o l . (Ber l .) 41 (I*

Ortega, S. 1981. Environmental s t ress, compet i t ion and dominance of ~ r a s s o s t r e a v i r g i n i c a 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 . (Berl .) 62(1):47-56.

Palmer, R.E. 1980. Behavioral and rhythmic aspects o f f i l t r a t i o n i n t h e bay . s c a l l o p , Argopecten i r r a d i a n s concentr icus, and t h e oyster, Crassostrea v i r i n i ca . J. Exp. Mar. B i o l . Ecol *281.

Parr ish, F.K. 1969. Ea r l y molluscan development. Proceedi ngs o f t h e conference on she1 l f i s h cu l tu re . Regional Marine Resources Coun- c i 1, Hauppange, N .Y.

Pierce, M.E., and J.T. Conover. 1954. A s tudy o f t h e growth of oysters under d i f f e r e n t eco log ica l con- d i t i o n s i n Great Pond. B i o l . B u l l . (Woods Hole) 107: 318. (Abstr.)

P r i c e , K.S., Jr., and D.L. Maurer. 1971. Ho ld ing and spawning Delaware Bay oys te r Crassostrea v i r g i n i c a out o f season. 11. Temperature requ i rements f o r maturat ion o f gonads. Proc. Natl . Shel l f i s h . Assoc. 61: 29-34.

Pr ice, A.H., C.T. Hess, and C .W. Smith. 1975. Observations o f Crassostrea v i r g i n i c a cu l tu red i n t h e heated e f f l u e n t and d i s - charged radionucl ides o f a

nuc lear power reactor . Proc. Nat l . Shel l f i s h . Assoc. 66: 54-68.

Pruder, G.D. 1975. Engineer ing aspects o f b i v a l v e molluscan mar icu l tu re : c u l t u r e system conf igura t ions . Col lege o f Marine Studies, U n i v e r s i t y o f Delaware, Newark. 13 PP.

Prytherch, H.F. 1929. Inves t i ga t i ons o f t h e phys ica l cond i t ions c o n - t r o l l i n g spawning o f oysters and t h e occurrence, d i s t r i b u t i o n , and s e t t i n g o f oys ter la rvae i n M i 1 - f o r d Harbor, Connecticut. B u l l . U.S. Fish. C o n . 44: 429-503.

Quick, J.A., J r . 1971. Patho log ica l and p a r a s i t o l o g i c a l e f f e c t s o f e levated temperatures on t h e oys- t e r Crassostrea v i r g i n i c a w i t h emphasis on t h e pathogen Lab r i n thorn xa marina. Pages lo&; hi., ed. A p r e l i m c nary i nves t i ga t i on : t h e e f f e c t of e levated temperature on the Amer- i can oys ter ~ r a s s o s t r e a v i r g i n i c a (Gmelin). F la . D ~ D . Nat. Resour. Prof. pap. Ser. 15. 190 pp.

Rhoads, D.C. 1973. The in f luence o f deposi t - feed ing benthos on water t u r b i d i t y and n u t r i e n t recyc l ing . Am. J. Sci. 273: 1-22.

R i t ch ie , T.P., and R.W. Menzel. 1969. In f l uence of l i g h t on l a r v a l se t t lement o f American oysters. Proc. Na t l . Shel l f ish . Assoc. 59: 116-120.

Rockwood, C.E., and W.F. Mazek. 1977. Seasonal va r ia t i ons i n oys te r meat y i e l d s i n Apalachicola Bay, F lo r i da . B u l l . Mar. Sci. 27(2): 346-347.

Rosenf ie ld, A. 1971. Oyster diseases o f North 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 propagat ion o f com- m e r c i a l l y valuable s h e l l f i s h . U n i 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 pro longed exposure t o e leva ted temperatures on t h e b iochemical cons t i t uen t s , gonadal development, 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 . Crassostrea v i rg i 'n ica . " cornp. Biochem. Phys i o l . 51B ( 2 ) : 157-164.

Sch lesse lman, G.W. 1955. The G u l f coas t o y s t e r i n d u s t r y o f t h e Un i t ed S ta tes . Geograph. Rev. 45(4) : 531-541.

S e l i g e r , H.H., J.A. Boggs, R.B. R i v k i n , W.H. B igg ley , and K.R.H. Aspden. 1982. The t r a n s p o r t o f o y s t e r l a r v a e i n an estuary. Mar. B i o l . ( B e r l .) 71(1) : 57-72.

Shaw, R., D.C. Arnold, and W.P. S t a l l - wor thy. 1970. E f f e c t s o f l i g h t on spa t se t t l emen t o f t h e Ameri- can oys te r , Crassostrea v i r i n i c a J. F ish . Res. Board. Can +?7c?

Shumway , S .E . 1982. Oxygen consumpt i o n i n oys te rs : an overview. Mar. B i o l . L e t t . 3: l -23.

S idwe l l , V.D., A.L. Loomis, and R.M. Grodner . 1979. Geog raph i c and monthly v a r i a t i o n i n composi t ion o f oys te rs , Cra-ssostrea v i r i n i c a . Mar. F ish . +17.

Rev.

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 species w i t h spe- c i a l r e fe rence t o oys te rs and o y s t e r d r i 11s. Ecology 31: 109- 118.

S t e i nberg, P.D., and V.S. Kennedy. 1979. P reda t i on upon Crassostrea v i r g i n i c a (Gmelin) l a r v a e by two i n v e r t e b r a t e species common t o Chesapeake Bay oys te r bars. Vel i ger 22: 78-84.

Stenzel , H.B. 1971. Oysters. Pages N953-N1224 i n K.C. Moore, ed. T r e a t i s e on i n v e r t e b r a t e paleon-

t o l ogy . P a r t N, Vol. 3. Mol lusca 6. Geol. Soc. Am. , Boulder , Colo. and U n i v e r s i t y o f Kansas, Lawrence.

Tinsman, J.C., and D.L. Maurer. 1974. E f f e c t s o f a thermal 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 E , eds. Thermal ecology. Proc. Symp., Augusta, Ga. M a y 3-5, 1973. N a t l . Tech. I n f . Serv. S p r i n g f i e l d , Va., ISBN 0-87079-014-X.

Tweed, S.M. 1973. Se t t lement and sur - v i va l o f Crassostrea v i r g i n i c a on De laware Bay seed o y s t e r beds. Proc. N a t l ." s h e l l f i s h . Assoc. 64: 8-9.

Ulanowicz, R.E., W.C. Cap l ins , and E.A. Dunnington. 1980. The f o r e c a s t i n g o f o y s t e r ha rves t i n c e n t r a l Chesapeake Bay. Estuar. Coasta l Mar. S c i . 11:lOl-106.

Veal, C.D., W.H. Brown, and W.J. Demoran. 1972. Devel opments i n o f f - b o t t o m o y s t e r c u l t u r e i n M i s s i s s i p p 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 s u r v i v a l o f t h e American o y s t e r Crassos- t r e a v i r g i n i c a near Oxford, Mary- land, 1961-62. U.S. F i sh W i l d l . Serv. Spec. Sc i . Rep. F i sh . No. 567. 6 pp.

Wells, H.W. 1961. The fauna o f o y s t e r beds, w i t h s p e c i a l re fe rence t o t h e s a l i n i t y f a c t o r . Ecol . Monogr. 31: 239-266.

Wood, L., and W.J. Hargis,Jr. 1971. T ranspor t o f b i v a l v e l a r v a e i n a t i d a l es tuary . Pages 29-44 i n D.J. Cr isp , ed. Four th ~uropea?; Mac01 . Symposium. Cambridge Universi ty Press, U.K.

Yonge, C.M. 1960. Oysters. Wi l lmer B ro the rs and Haran, Ltd., Birkenhead, England. 209 pp.

~ 0 2 7 1 - r or REPORT DOCUMENTATION 7- I. n*clpl.-l s b , : . r* s \ ,,- xe 1

PAGE 4. Tdle and subtaste 1 s R e o n oste I

I ..

1). SuoplemenIary Nates I- * U.S. Army Corps o f Engineers r e p o r t No. TR EL-82-4 I

Species P r o f i 1 es: L i f e H i s t o r i e s and Environmental Requirements o f Coast-a1 F ishes and I n v e r t e b r a t e s (Mid-At lant ic ) - -Amer ican

--- o y s t e r ts

1986

1 s Abstract (limit: 20Q words)

7. Author(%)

Jon G. S tan ley and Mark A. S e l l e r s -- 9. Pedormma Oqanixetlon Name and Address

Maine Cooperat ive F i she ry Research U n i t

Species p r o f i l e s a r e 1 i t e r a t u r e summaries o f t h e taxonomy, morphology, range, 1 i f e h i s t o r y , and environmental requ i rements o f coas ta l a q u a t i c species. They a r e designed t o a s s i s t i n environmental impact assessment. The American o y s t e r (Crassostrea v i r g i n i c a ) i s an impor- t a n t commercial and m a r i c u l t u r e species. I t i s t h e dominant species i n many bays and o y s t e r s h e l l s form ex tens i ve r e e f s t h a t mod i f y sed imenta t ion and l o c a l cur rents , Spawning occurs repea ted ly d u r i n g warmer months w i t h m i l l i o n s o f eggs re leased. Embryos and l a r v a e a r e c a r r i e d by c u r r e n t s th roughout t h e e s t u a r i e s and oceanic bays where o y s t e r s occur . The few s u r v i v i n g l a r v a e cement themselves t o s o l i d o b j e c t s f o r t he remainder o f l i f e .

--- -----.-.- a. PbflOrmlns Orsantral~on Rem. NO

__----.-----.--___._ 10. ~ID~ect /Tash/Work UnaC Re.

Upable t o move, t hey must t o l e r a t e changes i n t h e environment t h a t range from -1.7' t o 49 OC, 5 t o 30 p p t s a l a i n i t y , and c l e a r t o muddy water . The d i s t r i b u t i o n and abundance of a d u l t s a r e l i m i t e d by mar ine predators , so t h a t o y s t e r s a r e l i m i t e d l a r g e l y t o b r a c k i s h waters.

313 Murray Hal 1 - A___

11. ContrecItC) or GranI(C1 No.

U n i v e r s i t y o f Maine (c)

Orono, ME 04469 (C)

I t Sponsorins Orsenlxmtlon Name end Address

Nat iona l Wet1 ands Research Center U. S. Army Corps o f Engineers F i s h and W i l d l i f e Se rv i ce Waterways Exp. S t a t i o n U.S. Dept. o f t h e I n t e r i o r P.O. Box 631 Washington, DC 20240 Vicksburg, MS 39180

E s t u a r i e s Sediments Oxygen Oysters Feeding h a b i t s Compet i t ion Growth L i f e c y c l e s Feeding I b. ldenIlfie#a/0ln.Cnded Tmrms

American o y s t e r

I ~ r a s s o s t r e a v i r g i n i c a S a l i n i t y requ i rements I ~ e m p e r a t u r e r e q u i renen t s

C. COSATI fieldIGmup - . - - - , - .- . ---- . - - .. . . --

18. Avalleblliiy StatbmmnI 19. fccuraty Class CIhar Reoon)

U n c l a s s i f i e d

U n c l a s s i f i e d Unl i m i t e d Re1 ease 20. Srcurmly CIarr Uhi* Pas*)

.-- ---- ..--.- (see A N S I - Z ~ ~ . ~ ~ ) OPTIONAL FORM 272 (em

TAKE A PRIDE 212 Amerzcd

DEPARTMENT OF THE INTERIOR U.S. FISH AND WILDLIFE SERICE

As the Nation's principal conservation agency. the Department of the Interior has responsibility for most of 0ur.nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our flsh and wildlife, preserving thsenvironmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department as- sesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

species profiles: life histories and environmental ... · and invertebrates (mid-atlantic) american...

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