Species Profiles: Life Histories and EnvironmentalRequirements of Coastal Fishes and

Invertebrates (North Atlantic): American Lobster

Item Type monograph

Authors MacKenzie, Chet; Moring , John R.

Publisher U.S. Army Corps of Engineers, Coastal Ecology Group, WaterwaysExperiment Station.

Download date 08/09/2021 22:31:46

Link to Item http://hdl.handle.net/1834/21283

Do Not Remove from the Library U. S. Fish and Wildlife Service

L

Biological Report 82(11.33) I

r

700 Cajun Dome Boulevard TR EL-82.4 April 1985

Lafoyette, Louisiana 70506

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

AMERICAN LOBSTER

Coastal Ecology Group Fish and Wildlife Service Waterways Experiment Station U.S. Department of the Interior U.S. Army Corps of Engineers

T h i s i s one o f t h e f i r s t r e p o r t s t o be p u b l i s h e d i n t h e new " B i o l o g i c a l R e p o r t " s e r i e s . T h i s t e c h n i c a l r e p o r t s e r i e s , pub1 i shed b y t h e Resea rch and Deve lopmen t b r a n c h o f t h e U.S. F i s h and W i l d l i f e S e r v i c e , r e p l a c e s t h e "FWS/OBS1' s e r i e s p u b l i s h e d f r o m 1976 t o Sep tember 1984 . The B i o l o g - i c a l R e p o r t s e r i e s i s d e s i g n e d f o r t h e r a p i d p u b l i c a t i o n o f r e p o r t s w i t h an a p p l i c a t i o n o r i e n t a t i o n , and i t c o n t i n u e s t h e f o c u s o f t h e FWS/OBS s e r i e s on r e s o u r c e management i ssues and f i sh and w i l d l i f e needs .

B i 01 og i ca l Report 82(11.33) TR EL-82-4 Ap r i 1 1985

Species Prof i 1 es: L i f e Hi s t o r i e s and Environmental Requirements o f Coastal Fishes and Inver tebra tes (North A t l a n t i c )

AMERICAN LOBSTER

Chet MacKenzie and John R. Moring

Maine Cooperative F ishery Research U n i t Department o f Zoology

313 Murray H a l l U n i v e r s i t y o f Maine Orono, ME 04469

P r o j e c t Manager Lar ry Shanks

P ro jec t O f f i c e r John Parsons

Nat ional Coastal Ecosystems Team 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 Coastal Ecol ogy Group

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

Vicksburg, MS 39180

and

Nat ional Coastal Ecosystems Team D i v i s i o n o f B i o l o g i c a l Services

Research and Development F i sh and W i l d l i f e Serv ice

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

Th is s e r i e s should be re fe renced as f o l l ows :

U.S. F i s h 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 i nve r teb ra tes . U. S. F i s h W i l d 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 f o l l ows :

MacKenzie, C . , and J.R. Moring. 1985. Species p r o f i l e s : l i f e h i s t o r i e s and environmental requi rements o f coas ta l f i s h e s and i nve r teb ra tes (Nor th At1 a n t i c ) --American l o b s t e r . U.S. F i s h W i l d l . Serv. B i o l . Rep. 82(11.33). U.S. Army Corps o f Engineers, TR EL-82-4. 19 PP.

PREFACE

This species p r o f i l e i s one o f a ser ies 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 , cornmerci a1 , o r ecological importance. The p r o f i l es are designed to provide 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 the 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 requ i re - ments o f the species and t o descr ibe how populat ions o f t he species may be expected t o reac t t o environmental changes caused by coasta l development. Each p r o f i l e has sect ions on taxonomy, 1 i f e h i s t o r y , ecol og ica l r o l e , envi ronmental requirements, and economic importance, i f appl icable. A t h ree - r i ng b inder i s used f o r t h i s ser ies so t h a t new p r o f i l e s can be added as they a re prepared. This p r o j e c t i s j o i n t l y planned and f inanced by the U.S. Army Corps o f Engineers and the U.S. Fish and W i l d l i f e Service.

Suggestions o r quest ions regard ing t h i s r e p o r t should be d i r e c t e d t o one o f the f o l l o w i n g addresses.

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

U.S. Army Engineer Waterways Experiment S t a t i o n A t ten t i on : WESER-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. Customary

Mu1 t i p l y ' !?Y To Ob ta i n

m i l 1 ime te r s (m) cen t imete rs (an) meters (m) k i 1 m e t e r s ( km)

2 square mete rs (m ) 10.76 square k i 1 m e t e r s ( km2) 0.3861 hec ta res (ha) 2.471

l i t e r s ( 1 ) cub i c mete rs (m3) cub i c meters

inches inches f e e t m i l es

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

gal 1 ons cub i c f e e t acre- f e e t

m i l l igrams (mg) 0.00003527 ounces grams ( g ) 0.03527 ounces k i log rams (kg ) 2.205 pounds m e t r i c tons ( t ) 2205.0 pounds m e t r i c tons 1.102 s h o r t tons k i 1 ocal o r i e s ( kca l ) 3.968 B r i t i s h thermal u n i t s

Ce ls ius degrees 1.8(C0) + 32 Fahrenhe i t degrees

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

inches 25.40 inches 2.54 f e e t ( f t ) 0.3048 f a thorns 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 ) acres 2 square m i l e s (mi )

ga l 1 ons ( gal ) 3.785 cub i c f e e t ( f t 3 ) 0.02831 acre- f e e t 1233.0

ounces (02) 28.35 pounds ( I b ) 0.4536 s h o r t t ons ( t o n ) 0.9072 B r i t i s h thermal u n i t s (B tu ) 0.2520

m i l 1 imete rs cen t imete rs meters meters k i l ometers k i 1 ometers

square meters hectares square k i l ometers

1 i t e r s c u b i c meters cub ic meters

grams k i 1 og rams m e t r i c tons k i 1 ocal o r i es

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

CONTENTS

Page

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i ii CONVERSION TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i

NOMENCLATURE/TAXONOMY/RANGE . . . . . . . . . . . . . . . . . . . . . . . 1 MORPHOLOGY/IDENTIFICATION AIDS . . . . . . . . . . . . . . . . . . . . . 2 REASON FOR INCLUSION I N SERlES . . . . . . . . . . . . . . . . . . . . . 2 LIFE HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Spawning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 EggsandFecund i t y . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Prelarvae and Larvae . . . . . . . . . . . . . . . . . . . . . . . . . 4 Juven i les and Adu l ts . . . . . . . . . . . . . . . . . . . . . . . . . 5

MOLTING AND GROWTH CHARACTERISTICS . . . . . . . . . . . . . . . . . . . 5 FISHERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maine 7 New Hampshire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Massachusetts 8 POPULATIONDYNAMICS . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 ECOLOGICAL ROLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Feeding Hab i ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Predat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Diseases and Paras i tes . . . . . . . . . . . . . . . . . . . . . . . . 10

ENVIRONMENTAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . 11 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 S a l i n i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 DissolvedOxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

. . . . . . . . . . . . . . . . . . . . . . . . . . . . LITERATURECITED 15

ACKNOWLEDGMENTS

For rev iewing t h i s manuscript, t h e authors thank Robert C. Bayer, Professor o f Animal and Veter inary Sciences, U n i v e r s i t y o f Maine a t Orono, and Robert S. Steneck, Research Ass i s tan t Professor i n Zoology, I r a Dar l i n g Center, Walpole, Mai ne.

F i gure 1. A m e r i can l o b s t e r , Homarus ameri canus. --

AMERICAN LOBSTER

NOMENCLATURE /TAXONOMY /RANGE

S c i e n t i f i c name.... Homarus americanus ........ P r e f e r r e d common name American l o b s t e r ( F i g u r e 1).

Other cornmon names .......... l o b s t e r , Maine l o b s t e r , no r t he rn l o b s t e r , b l u e s h e l l s ( c o l o r v a r i a n t ) , ha rd s h e l l l o b s t e r , o l d s h e l l l o b s t e r ; b l a c k s h e l l , c rack backer ( l o b s t e r s p r e p a r i n g t o m o l t ) ; shedder, s o f t s h e l l , new s h e l l , shadow, rubber s h e l l , paper s h e l l , and buck l e she1 1 ( r e c e n t l y mo l ted l o b s t e r s ) ( H e r r i ck 1895).

C lass ...................... Crustacea Order ........................ Oecapoda Fami ly .................... Nephropidae

Geographi c range: American 1 obs te r s i n h a b i t t h e c o a s t a l and o c e a n i c waters o f t h e A t l a n t i c Ocean from Labrador south t o No r t h Ca ro l i na ( H e r r i c k 1 9 0 9 ) . They l i v e f r o m t h e i n t e r t i d a l zone ou t t o a depth o f 720 meters (McRae 1960). Ma jo r coas ta l concen t ra t i ons o f l o b s t e r a r e i n t h e G u l f o f Maine and t h e c o a s t a l w a t e r s o f New B r u n s w i c k and Nova S c o t i a , Canada (Cooper and Uzmann 1980). American l o b s t e r s a r e w i d e l y d i s t r i b u t e d i n most o f t h e coas ta l waters o f t h e no r t heas te rn U n i t e d S ta tes . Ma jo r o f f s h o r e concen t ra t i ons a re a long t h e o u t e r edge o f t h e Con t i nen ta l She l f and upper s lope between t h e eas te rn p a r t o f Georges Bank and

t h e o f f i n g o f Delaware Bay (Schroeder 1959). Small numbers i n h a b i t t h e o u t e r edge o f t h e Nova Sco t i an s h e l f (Cooper and Uzmann 1980).

MORPHOLOGY /IDENTIFICATION AIDS

The Amer i can l o b s t e r has f i v e cephal i c and e i g h t t h o r a c i c segments f used t o g e t h e r t o form a cephalothorax, wh ich i s covered by a sh i e l d -1 i ke carapace (F i gu re 1 ) . A l l t h e segments compr is ing t h e cephal o t horax bear appendages. Beg inn ing a n t e r i o r l y , t h e appendages o f t h e c e p h a l o t h o r a x a r e t h e f i r s t antennae, second antennae, mandibles, f i r s t maxi 11 ae, second maxi 11 ae, f i r s t , second, and t h i r d m a x i l l i p e d s and f i v e p a i r s o f w a l k i n g l e g s , o r pere iopods ( P h i l l i p s e t a l . 1980). The f i r s t t h r e e p a i r s o f pere iopods a r e che la te , t h e f i r s t p a i r mod i f ied i n t o

. l a r g e claws. O n e c l a w o f t h i s p a i r , t h e crusher , i s l a r g e r t han t h e o t h e r claw, t h e c u t t e r . American 1 obs te r s have compound eyes t h a t a re movable and s t a l ked .

The s i x body segments p o s t e r i o r of t h e carapace make up t h e abdomen. Pai red, b i ramous p l eopods a re 1 ocated on t h e f i r s t f i v e abdominal segments. The l a s t abdominal segment c o n s i s t s o f t h e t e l son f lanked by uropods, which a r e m o d i f i e d pleopods. The broad t a i l f i n , composed o f t h e t e l son and u ro - pods, i s used f o r backward swimming, which i s c h a r a c t e r i s t i c o f l o b s t e r s .

The f i r s t p a i r o f p l e o p o d s on male l o b s t e r s a r e m o d i f i e d i n t o r i g i d s t r u c t u r e s , gonapods, which a re used t o convey sperm t o t h e female (Cobb 1976). I n females, t h e f i r s t p a i r of pleopods a r e s i m i l a r t o t h e o t h e r s b u t a r e much sma l le r . There a r e two c h a r a c t e r i s t i c s used t o separa te t h e sexes o f mature l o b s t e r s . Males have sharp sp ines under t h e abdomen; female sp ines a r e b l u n t . The ma le ' s abdomen i s n a r r o w e r t h a n t h e w i d t h o f t h e

carapace; t hose i n t h e female a r e about equal (Cobb 1976).

American l o b s t e r s a r e no rma l l y g reen i sh-brown bu t some specimens a r e b lue, red, r edd i sh-ye1 low, cream, b lack, o r c a l i c o ( H e r r i c k 1895).

The l a r g e s t American l o b s t e r s a r e males (Wol fe 1978). The l a r g e s t male on r eco rd weighed 19.25 kg, and was 63.4 cm l o n g . The h e a v i e s t f e m a l e weighed 8.35 kg (A iken 1980).

The t o t a l p r o p o d i t e l e n g t h i n r e l a t i o n t o carapace l e n g t h i s a means o f d i s t i n g u i s h i n g between t h e 1 a r v a l s tages o f t h e American l o b s t e r and t h e ~ u r o p e a n 1 obs te r , Homarus gammarus ( G r u f f y d d e t a l . 19 t5 ) .The t o t a l p r o p o d i t e l e n g t h i s g r e a t e r t han t h e carapace l e n g t h o f t h e European l o b s t e r la rvae . The o p p o s i t e i s t r u e f o r American l o b s t e r la rvae . Geographic i s o l a t i o n i s t h e o n l y c h a r a c t e r t h a t d i s t i n g u i s h e s t h e a d u l t s o f t h e two spec ies ( C o r r i v a u l t and Tremblay 1948; as c i t e d i n G ru f f ydd e t a1 . 1975).

REASON FOR INCLUSION IN SERIES

Amer i can 1 o b s t e r s s u p p o r t an impo r t an t commerci a1 f i s h e r y a long t h e no r t heas te rn coas t o f t h e U.S. They a r e abundant i n coas ta l and o f f sho re w a t e r s . I t i s i m p o r t a n t t h a t t h e impact o f development p r o j e c t s on l o b s t e r popu la t i ons be cons idered so t h a t t h i s impo r t an t and va l uab le n a t u r a l resource w i l l be p ro tec ted .

LIFE HISTORY

Spawni n q

Ma le American l o b s t e r s mature a t s h o r t e r l eng ths t han females. Most ma1 es c a r r y v i a b l e spermatozoa when t h e carapace 1 ength (CL) (measured f rom t i p o f ros t rum t o t h e back o f t h e carapace) i s 40 t o 45 mm. About 50% of t h e males examined a long t h e Maine

coas t were p h y s i o l o g i c a l l y mature a t 44 mm CL: t h e sma l l es t mature male was 41 mm CL (Krouse 1973). Females i n Maine mature when they a re about 90 mm CL (Krouse 1973) bu t i n warmer waters (Long I s l a n d Sound), most mature a t l e n q t h s o f 70 t o 74 mm CL ( ~ e m ~ l e i a n 1936b; B r i ggs and Mushacke 1979).

Small males u s u a l l y cannot mate success fu l l y w i t h 1 a r g e r f m a 1 es (Templeman 1934, 1935). Males may be capable o f p roduc ing mature sperma- tozoa when they a re 40-45 mm CL b u t t h e y may n o t be c a p a b l e o f m a t i n g u n t i l t hey a r e as l a r g e as t h e smal l e s t mature females.

When spawning, l o b s t e r s p a i r f o r a b o u t 2 weeks (Atema e t a l . 1979) . Femal es 1 eave t h e i r so l i t a r y she1 t e r s about 7 days b e f o r e m o l t i n g and share t h e s h e l t e r of a dominant, t e r r i t o r i a1 ma1 e.

A f e m a l e sex pheromone i s p r o - duced b e f o r e o r a t t h e t i m e of m o l t i n g . Thi s pheromone suppresses ma1 e aggress ion and induces c o u r t s h i p (McLeese 1970; Atema and Engstrom 1971). Pre-mol t behavi o r a l d i sp l ays a re a l s o impo r t an t i n successful p a i r f o rma t i on (Atema e t a l . 1979). Ma t i ng u s u a l l y takes p l a c e 20-40 minutes a f t e r t h e f e m a l e m o l t s , b u t t o be success fu l , mat ing must t a k e p l a c e w i t h i n a few hours ( r a r e l y more than one) a f t e r t h e female has mol ted. One female, however, was r epo r t ed t o have s u c c e s s f u l l y mated 12 days a f t e r m o l t i n g (Templ eman 1936a). Successful mat ing o f ha rd s h e l l e d female l o b s t e r s severa l months a f t e r m o l t i n g has been repo r t ed (Dunham and Sk i nner-Jacohs 1978; A iken and Waddy 1980a).

The m a l e mounts t h e f e m a l e and t u r n s her over w i t h h i s w a l k i n g l e g s and maxi 11 ipeds. The male p laces h i s gonapods i n t h e f e m a l e s e m i n a l r e - cep tac l e ( the lycum) and depos i t s a spermatophore ( H e r r i ck 1895; Hughes and M a t t h i e s s e n 1962; Atema e t a l . 1979). Ma t i ng u s u a l l y i s completed i n

a h o u t 30 seconds ; t h e l o n g e s t i n 3 minutes (Atema e t a l . 1979). Males l a r g e r t han t h e female a re most suc- c e s s f u l a t c o p u l a t i on (Templeman 1934, 1935 ) . Ma les p r o t e c t f ema les f rom p r e d a t i o n and cann iba l i sm f o r up t o 7 days d u r i n g t h e v u l n e r a b l e post-mol t stage. T h i s " p r o t e c t i o n " by t h e male a l s o ensures t h a t o t h e r males wi 11 no t copu la te w i t h h i s mate (Atema e t a l . 1979).

Eggs a r e no rma l l y ex t ruded 11 t o 13 months a f t e r mat ing. As ova a r e re leased, t hey a r e f e r t i l i z e d by p a r t o f t h e spermatozoa s t o r e d i n t h e seminal r e c e p t a c l e (Templ eman 1936a: Krouse 1973). Ov ipos i t i o n occurs on a two yea r c y c l e even i f t h e female i s n o t c a r r y i n g spermatozoa. Evidence i s s t r o n g t h a t eggs a r e f e r t i 1 i zed e x t e r n a l l y as t hey pass over t h e semi- na l r ecep tac l e (A iken and Waddy 1980a), b u t Farmer (1974) be1 i eves t h a t f e r t i l i z a t i o n i s i n t e r n a l .

Females a re capable o f f e r t i l i z - i n g a t l e a s t two success ive batches of eggs f rom a s i n g l e mat ing (Templeman 1936a; A iken and Waddy 1980a; Campbell 1983). La rge females do no t mo l t o r mate every year .

Eggs and Fecund i t y

F r e s h l y ex t ruded American l o b s t e r eggs a re dark green and i r r e g u l a r l y shaped. They soon become s p h e r i c a l and t e l o l e c i t h a l , and a re about 1.5 t o 1.7 mm i n d i ameter ( H e r r i c k 1909). As eggs develop, t hey i nc rease i n s i z e and become e longa ted and l i g h t e r i n c o l o r .

The number o f eggs i n a c l u t c h ranges f rom 3,000 t o 115,000 ( H e r r i c k 1909; S a i l a e t a? . 1969; Pe rk i ns 1971). The 1 oga r i thmi c re1 a t i o n s h i p between average f e c u n d i t y (Y) and carapace l e n g t h (CL) o f l o b s t e r s c o l l e c t e d f rom i n s h o r e wa te rs o f f Rhode I s 1 and and Massachusetts (Sai 1 a e t a l . 1969) i s :

loglO Y = -1.6017 + 2.8647 loglo CL.

The e s t i m a t e d f e c u n d i t y - 1 e n g t h (CL) r e l a t i o n s h i p o f l o b s t e r s from t h e C o n t i n e n t a l She1 f o f f s o u t h e r n New England i s : I n Y = -5.0231 + 3.1569 I n CL ( P e r k i n s 1971) . I n d i v i d u a l v a r i a t i o n i n f e c u n d i t y i s l a r g e (Squ i r e s 1970) .

A f t e r e x t r u s i o n , f e r t i l i z e d eggs become f i r m l y a t t a c h e d t o p leopods, w h e r e t h e y d e v e l o p f o r 9 - 1 1 m o n t h s ( A i k e n and Waddy 1980a) . About 36% o f t h e eggs a r e l o s t between e x t r u s i o n and h a t c h i n g ( P e r k i n s 1 9 7 1 ) . Tem- p e r a t u r e i s a key f a c t o r t h a t d e t e r m i n e s t h e l e n g t h o f t i m e t h e eggs a r e c a r r i e d on t h e p leopods (Templeman 1940; A i k e n and Waddy 1980b). Eggs d e v e l o p t o t h e 16 c e l l s t a g e i n two days a t 18.5OC, and 4.8 days a t 10.5OC (Temp1 eman 1940).

L o b s t e r eggs h a t c h f r o m May t o October ; t h e warmer t h e w a t e r t h e e a r l i e r t h e h a t c h . I n Massachuset ts , eggs b e g i n h a t c h i n g i n m id o r l a t e May when w a t e r t empera tu res a r e about 15OC (Hughes and M a t t h i e s s e n 1962). Peak h a t c h i n g i s i n June a n d e a r l y J u l y when w a t e r t e m p e r a t u r e s reach 20°C. The t i m e r e q u ' i r e d t o h a t c h a l l t h e e g g s w i t h i n a b r o o d depends on t h e w a t ~ r t empera tu re . A l l eggs w i t h i n a b rood u s u a l l y h a t c h i n 2 t o 3 days a t 20°C, and i n 10-14 days a t 15OC (Hughes and M a t t h i e s s e n 1962).

Females r e l e a s e l a r v a e d u r i n g a b r i e f p e r i o d a t n i g h t by a c t i v e l y b e a t i n g t h e i r p l eopods (Enn i s 1975). Females n o r m a l l y m o l t and mate w i t h i n one month a f t e r t h e i r b r o o d has h a t c h - ed.

P r e l a r v a e and L a r v a e

American l o b s t e r s pass t h r o u g h one p r e l a r v a l and f o u r f ree-swimmi ng l a r v a l s tages b e f o r e s e t t l i n g t o t h e b o t t o m and m o l t i n g i n t o j u v e n i l e s . M o s t p r e l a r v a e m o l t i n t o t h e fi r s t l a r v a l s t a g e b e f o r e b e i n g r e l e a s e d by females (Dav is 1964). A l l l a r v a l s tages a r e n o r m a l l y comple ted i n 25-35 days, b u t t h e l e n g t h o f t i m e i s

t e m p e r a t u r e dependent (Tab1 e 1 ) . H e r r i c k (1895, 1909) d e s c r i b e s and d iagrams each o f t h e f o u r l a r v a l s tages .

The d i s t r i b u t i o n and abundance o f 1 a r v a e a r e a f f e c t e d by t h e d i s t r i bu- t i o n o f spawning females, s u r f a c e c u r r e n t v e l o c i t y and d i r e c t i o n , tem- p e r a t u r e , s a l i n i t y , l i g h t i n t e n s i t y , h y d r o s t a t i c p ressu re , and 1 a r v a l m o r t a l i ty (Ph i 11 i p s and S a s t r y 1980) . The l a r v a e a r e p l a n k t o n i c from l a t e May t o Oc tober ; t h e y appear e a r l i e r i n t h e p l a n k t o n i n s o u t h e r n New England t h a n i n t h e G u l f o f Ma ine ( F o g a r t y and L a w t o n 1 9 8 3 ) . S t a g e I l a r v a e w e r e c o l l e c t e d f r o m May t o e a r l y J u l y i n B l o c k I s l a n d Sound o f f Rhode I s l a n d ( B i b b e t a l . 1983) and f r o m June t o e a r l y August o f f t h e c o a s t of Maine (Sherman and Lew is 1967).

V e r t i c a l d i s t r i b u t i o n i s a f f e c t e d by 1 i g h t i n t e n s i t y (Templeman 1937, S c a r r a t t 1973, H a r d i n g e t a l . 1982) . A t n i g h t t h e l a r v a e seek deeper w a t e r s b u t r e t u r n n e a r t h e s u r f a c e d u r i n g day ( P h i l l i p s and S a s t r y 1980). Pho to - t a c t i c responses observed i n t h e l a b o r a t o r y d i f f e r e d among 1 a r v a l s tages and w i t h i n each l a r v a l s t a g e (Hadley 1905, 1908). S tage I and I V 1 a r v a e were o r i g i n a l l y p o s i t i v e l y p h o t o t a c t i c b u t became nega t i v e l y

T a b l e 1. The approx ima te number o f days r e q u i r e d by l a r v a e t o pass t h r o u g h each l a r v a l s t a g e a t d i f f e r e n t t e m p e r a t u r e s ( m o d i f i e d f ro,n d a t a by Templeman 1936a i n A i k e n 1980). - Temp. L a r v a l s tage

(OC) 1 2 3 -- 4 T o t a l 8 20 26 42

10 14 15 25 49 103 12 10 11 15 32 68 14 7 8 11 25 5 1 16 5 6 9 22 4 2 18 3 5 7 18 33 20 2 4 6 14 25 2 2 2 4 5 11 2 2 --

p h o t o t a c t i c l a t e i n each stage. Stage I 1 and I 1 1 l a r v a e were nega t i ve l y p h o t o t a c t i c bu t responses were h i g h l y v a r i able.

High l a r v a l d e n s i t i e s a long windward coas ts suggest t h a t l a r v a e a re t r anspo r ted by su r f ace c u r r e n t s (Fogar ty 1983). Preva i 1 i n g south- w e s t e r l y winds along t h e New England coast i n t h e summer may t r a n s p o r t l a r v a e f rom o f f s h o r e t o coas ta l wa te rs (Fogar ty 1983).

L a t e i n s tage I V , l a r v a e s e t t l e t o t h e b o t t o m and b u r r o w i n t o t h e subs t ra te . They m o l t i n t o j u v e n i l e s w h i l e she l t e red i n t h e i r burrows (Cooper and Uzmann 1980).

Juven i l es and Adu l t s

American l o b s t e r s i n i nsho re waters excavate s h e l t e r s under o b j e c t s r e s t i n g on t h e sea f l o o r when t h e r e a re no n a t u r a l c rev i ces a v a i l a b l e as shel t e r . H ighes t l o b s t e r d e n s i t i e s a re on sand subs t ra te w i t h o v e r l y i n g f l a t t e n e d rocks. Juveni 1 e and a d u l t 1 obs te r s a re n e g a t i v e l y p h o t o t a c t i c and p r e f e r d a r k s h e l t e r s shaped so t h a t t h e l o b s t e r can ma in ta i n con tac t w i t h t h e r o o f and w a l l s (Cobb 1971).

Lobs te rs i nsho re tend t o be s o l i t a r y . They r a r e l y share she l t e r s , and s h a r i n g b e h a v i o r has o n l y been repo r t ed i n w i n t e r when bottom water temperatures a re co ldes t (Cooper and Uzmann 1980). Lobs te rs o f f s h o r e o f t e n share s h e l t e r s o r bowl-shaped -depressions i n t h e subs t ra te . Th i s behav io r may be caused by t h e s c a r c i t y ' o f s h e l t e r s (Cooper and Uzmann 1980).

J u v e n i l e American l o b s t e r s l e s s than 35 mm CL r a r e l y l eave t h e i r shel t e r s (Cooper and Uzmann 1977). When j u v e n i l e s a re 35-40 mn CL t hey Len tu re j u s t o u t s i d e t h e i r s h e l t e r s a t n i g h t . When about 45 m CL they beg in noc tu rna l f o r a g i n g away f rom t h e i r she l t e r s . A d u l t and j u v e n i l e l o b s t e r s u s u a l l y t r a v e l l e s s t han 300 m f rom

t h e home s h e l t e r when f o rag ing (Cooper and Uzmann 1980).

Lobs te r s i nsho re move from shoal wa te r ( < 10 m) t o deeper water when storms generate heavy seas (Cooper e t a1 . 1975). These h o r i z o n t a l movements a re u s u a l l y 100 m o r l e s s bu t i n v o l v e an i n c r e a s e i n d e p t h up t o 10 m. Lobs te rs a1 ong t h e Canadian eas t coast make sho r t d i s t ance seasonal movements from re1 a t i v e l y deep waters (15-18 m) i n w i n t e r t o sha l lower wate rs (7-9 m) i n summer (Stasko 1980).

Lobs te rs i nsho re appear t o have a l i m i t e d home range. About 99% o f t h e l o b s t e r s (81-123 mm CL) recap tu red a f t e r t a g g i n g were w i t h i n 2.2 km from t h e re l ease s i t e (Cooper 1970). From 74% t o 98% o f t h e l o b s t e r s (81-116 mn CL) recap tu red a f t e r be ing re leased a t s i t e s a long t h e coast o f Maine were caught w i t h i n 8 km f rom t h e re l ease s i t e (Krouse 1973).

I n another study 22% o f t h e l a r g e mature l o b s t e r s (127-200 mm CL) t h a t were recaptured a f t e r be ing tagged and re leased i n Penobscot Bay, Maine, were caugh t 137 km t o 256 km f r o m t h e i r r e l ease p o i n t s (Dow 1974). Large l o b s t e r s apparen t l y m i g r a t e f a r t h e r than smal l 1 obsters .

Lobs te rs o f f s h o r e m i g r a t e g r e a t e r d i stances than t h e i r coas ta l coun te r - pa r t s . Movements o f up t o 345 km i n 71 days were repo r t ed by Uzmann e t a l . ( 1977 ) . Ground speeds ranged f r o m 0.18 t o 10.2 km per day; t h e median was 1.7 km.

MOLTING AND GROWTH CHARACTERISTICS

The growth o f l o b s t e r s i s c o n t i n - uous, b u t i t i s g r e a t e s t when t h e y m o l t ( P h i 1 l i p s e t a1 . 1980 ) . The g r o w t h r a t e depends on t h e m o l t i n g f r e q u e n c y and t h e s i z e i n c r e a s e a t mo l t i ng . Wi th i n c r e a s i n g age, Ameri can 1 obs te rs mo l t 1 ess f r e q u e n t l y and grow p r o p o r t i o n a l l y 1 ess a t each mo l t . Lobs te rs mo l t an average o f 10

, t i m e s i n t h e i r f i r s t y e a r , 3 o r 4 t imes i n t h e second and t h i r d years, t w i c e i n t h e f o u r t h yea r , and once a y e a r o r l e s s t h e r e a f t e r (Hughes and Mat th iessen 1962).

A l though s a l i n i t y , d i s s o l v e d oxygen, food ava i l a b i 1 i t y , and crowding a r e f a c t o r s t h a t a f f e c t growth ( P h i l 1 i p s e t a l . 1980), temperature appears t o be t h e dominant f a c t o r (Huntsman 1924; Temp1 eman 1936c; Hughes and M a t t h i essen 1962; Hughes e t a l . 1972; Gru f fydd e t a l . 1975). For example, c a p t i v e j u v e n i l e s h e l d two yea rs i n water w i t h a cons tan t temperature about 23°C weighed 454 g b u t those kep t a t ambient temperatures (2 " t o 24°C) took 5.5 y e a r s t o r e a c h t h e same w e i g h t (Hughes e t a1 . 1 9 7 2 ) . The h i g h e r growth r a t e was due t o a g r e a t e r number o f mo l ts , no t t o a change i n t h e r a t e o f growth between mo l ts .

The percentage i nc rease i n l e n g t h per m o l t o f l a r v a l l o b s t e r s c o l l e c t e d i n t h e Northumberland S t r a i t , southern G u l f o f S t . Lawrence, was 33% f r o m l a r v a l s tage I t o stage 11, 32% f rom s tage I 1 t o s tage 111, and 30% f rom s tage I 1 1 t o s tage I V (W i l de r 1953).

Es t imates o f t h e average percentage i nc rease i n l e n g t h pe r m o l t f o r j uven i l e s and a d u l t s ranged from 7% t o 20%; weight ga ins were 30% t o 61% (A iken 1980). Mature females have a s lower growth r a t e than males because femal es m o l t 1 ess f r e q u e n t l y . Growth between m o l t s f o r t h e two sexes i s s i m i l a r (W i l de r 1953). Other s t u d i e s have i n d i c a t e d t h a t t h e percentage i nc rease i n l eng ths o f mature females between m o l t s i s l e s s t han t h a t o f mature males o f t h e same s i z e (W i l de r 1963; Cooper and Uzmann 1971; Ennis 1972; Campbell 1983).

Lobs te r s o f f s h o r e (90 mm CL) grow f a s t e r (18% l e n g t h inc rease) pe r mo l t (Cooper 1970) than 1 obs te r s i nsho re ( 1 2 % ) t h a t a r e t h e same s i z e . The d i f f e r e n c e i n growth o f t h e two sexes

i s s l i g h t (2%) accord ing t o Cooper and Uzmann (1971). Lobs te rs o f f s h o r e m o l t more o f t e n than l o b s t e r s inshore. The d i f f e r e n c e i n growth r a t e s o f i nsho re and o f f s h o r e 1 obs te r s may be exp la ined by t h e m i g r a t o r y h a b i t s o f t h e t w o popu la t ions . Each y e a r o f f s h o r e l o b s t e r s m i g r a t e between t h e o u t e r Con t i nen ta l S h e l f and upper s l ope wate rs (8 " t o 12°C) and sha l lower Con t i nen ta l S h e l f waters (10" t o 17.5"C) seeking optimum water temperatures f o r growth, mo l t i ng , and e x t r u s i o n o f eggs (Cooper and Uzmann 1971, Uzmann e t a l . 1977) whereas i nsho re l o b s t e r s a r e nonmigratory and sub jec t t o w i n t e r temperatures (<5"C) t h a t i n h i b i t growth.

The a v e r a g e i n c r e a s e i n l e n g t h f o r l o b s t e r s (68-110 mm CL) captured, released, and recap tu red f o u r t o t w e l v e months l a t e r a long t h e Canadian e a s t c o a s t was 13% t o 15% w i t h an average weight i nc rease o f 43% t o 54% (Wi 1 der 1953). The average i nc rease i n l e n g t h per m o l t f o r l o b s t e r s (20-176 mm CL) a long t h e Maine coas t was 8% (Thomas 1973). He found t h a t t h e l e n g t h r e l a t i o n s h i p between prernolt and pos tmo l t f o r l o b s t e r s rang ing i n p remol t s i zes f rom 20 t o 176 mm CL was 1 i nea r .

Cooper and Uzmann (1980) d e t e r - mined t h e average growth increment p e r y e a r f o r l o b s t e r s o f f s h o r e t h a t mol t , and t h e annual p r o b a b i l i t y o f mo l t i ng .

FISHERY

American 1 obs te rs have been har - vested commerc ia l ly s i n c e t h e 18 th cen tu ry . I n t h e mid-19th century, t h e f i r s t 1 arge s c a l e e x p l o i t a t i o n o f l ob - s t e r resources was induced by t h e canning i n d u s t r y (Dow 1980). By t h e end o f t h e 19 th century, t h e m a j o r i t y o f l o b s t e r s were b e i n g s o l d t o t h e ' l i v e l o b s t e r i ndus t r y . Storage f a c i l- i t i e s ( o r pounds) were cons t ruc ted t o h o l d l i v e l o b s t e r s so t h a t m a r k e t s cou ld be r e g u l a r l y suppl ied. Canada and t h e Un i t ed S ta tes t o g e t h e r have

about 75 s t o r a g e f a c i l i t i e s w i t h an e s t i m a t e d c a p a c i t y o f 75 mi 1 l i o n l o b - s t e r s (Dow 1980) .

T r a d i t i o n a l l y , l o b s t e r s a r e caugh t i n b a i t e d t r a p s ( p o t s ) . Most l o b s t e r s a r e caugh t i n s h a l l o w (5-30m) i n s h o r e w a t e r s (Cobb 1976).

Land ings from t h e o f f s h o r e f i s h i n g grounds ( a l o n g t h e o u t e r edge o f t h e C o n t i n e n t a l S h e l f and t h e upper s l o p e f rom Georges Bank t o Chesapeake Bay a t dep ths f r o m lOOm t o 600m) i n c r e a s e d s h a r p l y f rom about 800,000 l b i n 1958 t o n e a r l y 9 m i l l i o n 1b i n 1 9 7 0 ( F i g u r e 2 ) . O f f s h o r e l o b s t e r 1 andi ngs have d e c l i n e d s i n c e 1971 t o about 5.6 m i l l i o n pounds i n 1983. D u r i n g t h e e a r l y y e a r s o f t h e o f f s h o r e l o b s t e r f i s h e r y , most v e s s e l s used o t t e r t r a w l s t o c a p t u r e l o b s t e r s , b u t s i n c e t h e l a t e 1960 ' s most v e s s e l s use l a r g e l o b s t e r p o t s s e t i n l o n g s t r i n g s

YEARS

F i g u r e 2. E s t i m a t e d i n c r e a s e i n c a t c h o f o f f s h o r e l o b s t e r s , 1940-70 (Cobb 1976).

(Cobb 1976), someth ing on t h e o r d e r o f a l o n g l i n e .

L o b s t e r s a r e caugh t t h r o u g h o u t t h e y e a r i n New England excep t f o r a r e s t r i c t e d area nea r Monhegan I s l a n d , Maine, wh ich i s c l o s e d t o l o b s t e r i n g f r o m January 1 t o June 25. The c a t c h i n New England i s h i g h e s t f r o m August t o November.

Maine

Mai ne produces t h e g r e a t e s t number o f l o b s t e r s . Land ings i n 1982 were 22.5 m i l l i o n pounds w i t h a d o c k s i d e v a l u e o f abou t $50 m i l l i o n (Tab le 2).

L o b s t e r s may o n l y be caugh t w i t h t r a p s t h a t a r e ven ted t o a1 low i n d i v i d u a l s s m a l l e r t h a n l e g a l s i z e t o escape. N e i t h e r t h e number o f t r a p s p e r f i she rman n o r t h e number o f 1 i censes i s r e s t r i c t e d . Minimum s i z e i s 3 3 /16 i n c h e s ( 8 1 mm) CLM (ca rapace l e n g t h measured f r o m t h e back @ f t h e eye s o c k e t t o t h e back o f t h e ca rapace) . Maine i s t h e o n l y s t a t e w i t h a maximum s i z e l i m i t ; a l l l o b s t e r s l a r g e r t h a n 5 i n c h e s (127 mm CLM) must be re leased .

Female l o b s t e r s c a r r y i n g eggs a t t a c h e d t o t h e i r p l eopods ( b e r r i e d ) h a v e been p r o t e c t e d i n a1 1 l o b s t e r p r o d u c i n g s t a t e s s i n c e t h e l a t e 1 9 t h c e n t u r y (Dow 1 9 8 0 ) . L o b s t e r s t h a t e x t r u d e eggs w h i l e b e i n g h e l d i n h o l d i n g pens i n Ma ine a r e purchased by t h e S t a t e , marked w i t h a "V" -notch i n t h e t e l s o n , and r e l e a s e d i n t h e sea. "V" -notched l o b s t e r s a re p r o t e c t e d i n Ma ine and must be r e l e a s e d whe the r o r n o t t h e y a r e b e r r i e d a t t h e t i m e o f r e c a p t u r e .

New Hampshire

L o b s t e r s i n New Hampshire a r e t a k e n b y t r a p s o r t r a w l . The t r a w l f i s h e r y i s n o t d i r e c t e d a t l o b s t e r s b u t an i n c i d e n t a l c a t c h o f l o b s t e r s i s a1 lowed. The 1982 commerc ia l c a t c h was 807,000 I b , v a l u e d a t $1.8 m i l l i o n

Table 2. Landings (thousands o f pounds) and dockside values (thousands o f do1 l a r s ) o f American l o b s t e r s i n Maine, New Hampshire, and Massachu- s e t t s fra 1963-1982. (F i she ry S t a t i s t i c s o f t h e Uni ted States, 1963-64, 1969-70; New England F i she r i es , 1971-76; N.M. F.S. unpubl ished data, 1977-82).

Mai ne New Hampshire Massachusetts Years Landings Val ue Landings Val ue Landings Val ue

Massachusetts (Table 2). The minimum s i z e l i m i t i n New Hampshire i s 3 3/16 inches ( 8 1 mm) The S ta te has a l i m i t e d e n t r y CLM. There i s no l i m i t t o t h e number inshore commercial f i s h e r y . I n 1983, of t r a p s t h a t can be s e t by commercial t h e number o f coas ta l l o b s t e r pe rm i t s l o b s t e r f ishermen. New Hampshire i ssued was l i m i t e d t o 1,608. Vented s e l l s a r e c r e a t i o n a l l o b s t e r 1 icense t r a p s a re used i n t h e coas ta l f i s h e r y ; t h a t a l l ows t h e ho lde r t o s e t 5 t r aps . t h e r e i s no 1 i m i t on t h e number o f

t r a p s t h a t can be s e t by each f i s h e r - man. An i n c i d e n t a l ca t ch o f 100 l o b s t e r s p e r day i s a l lowed f o r inshore t r a w l e r s . The number o f pe rm i t s f o r t h e o f f s h o r e f i s h e r y i s u n l i m i t e d and b o t h t r a p s and t r a w l s a r e l e g a l gear. The minimum l e n g t h i n Massachusetts i s 3 3/16 inches ( 8 1 mm) CLM.

Landings i n 1982 had a docks ide va lue o f $25,596,000 (Tab le 2 ) . Massachusetts has a 1 arge r e c r e a t i o n a l f i s h e r y . About 11,000 non-commercial l i c e n s e s were i ssued i n 1983. Permi t ho lde rs a r e a l lowed t o se t 10 l o b s t e r t r aps . Lobs te rs can be taken 1 egal l y by s k i n o r SCIIBA-divers i n Massa- c h u s e t t s b u t n o t i n t h e o t h e r New England S ta tes .

The New England Regional F ish- e r i e s Management Counc i l has developed a management p l a n f o r t h e o f f s h o r e (3-200 m i l e s ) 1 obs te r f i s h e r y t h a t w i l l t a k e e f f e c t on January 1, 1985. For example, t h e minimum l e n g t h l i m i t f o r o f f s h o r e l o b s t e r s w i l l be 3 3/16 inches (81 mm) CLM.

POPULATION DYNAMICS

Na tu ra l mor ta l i t y i s ext remely h i gh d u r i n g t h e free-swimming p l ank - t o n i c l a r v a l stages o f t h e American l o b s t e r . S c a r r a t t (1964, 1973) used l a r v a l s tage abundance t o es t ima te t h e s u r v i v a l f rom stage I t o s tage I V o f l a r v a e i n t h e s o u t h e r n G u l f o f S t . Lawrence , New B r u n s w i c k . Ave rage annual s u r v i v a l was about 0.9% (range 0.1 t o 2.5). The percentage s u r v i v a l may have been underest imated because o f t h e d i f f i c u l t y i n e s t i m a t i n g t h e abundance o f s tage I V l a r vae . Larvae become n e g a t i v e l y p h o t o t a c t i c midway th rough stage I V and may n o t have been c o l l e c t e d i n su r f ace tows t h a t were used t o es t ima te abundance ( S c a r r a t t 1973).

Es t imates o f mor ta l i t y o f j u v e n i l e and a d u l t l o b s t e r s i n U n i t e d S ta tes waters were reviewed by Anthony

(1980). Es t imates o f instantaneous t o t a l m o r t a l i t y (Z ) . f rom Maine, New Hampshire, Massachusetts, Rhode I s l a n d , New York, New Jersey, and V i r g i n i a averaged 1.84 ( range 0.91 t o 2.80). Est imates o f instantaneous n a t u r a l mor ta l i t y (M) ranged f rom 0.02 t o 0.35 w i t h an average o f 0.15. Mo r ta l i t y es t imates o f l o b s t e r popu la t i ons i n t h e Canadian Mar i t imes were reviewed by Campbell (1980).

S e v e r a l methods were used t o es t imate t h e m o r t a l i t y o f j u v e n i l e and a d u l t l o b s t e r s a long t h e coast of Maine (Thomas 1973). Ins tan taneous t o t a l m o r t a l i t y (Z ) o f commerc ia l -s ize l o b s t e r s ( > 81 mn) ranged f rom 1 .I363 t o 2.9188. Instantaneous n a t u r a l mor ta l i t y (M) f o r p r e - r e c r u i t ( l e s s than commerci a1 s i z e ) l o b s t e r s ranged f rom 0.0202 t o 0.3467. Es t imates o f instantaneous f i s h i n g m o r t a l i t y ( F ) ranged f rom 0.7896 t o 2.8986. These F va lues represen t an annual exp l o i t a - t i o n r a t e o f 54.6% t o 84.5% o f t h e 1 obs te r s vu lne rab le t o t h e commerci a1 f i s h e r y .

Annual e x p l o i t a t i o n r a t e s o f l o b s t e r s near Comfort Cove, New- foundland, were as h i gh as 95% (Ennis e t a l . 1982 ) . F o r 1977-81, annua l e x p l o i t a t i o n r a t e s o f l o b s t e r s near Not re Dame Bay, Newfound1 and, v a r i e d f rom 80% t o 95% (Ennis 1983).

Lobs te r movements u s u a l l y a r e t r i g g e r e d by changes i n wate r temperature (McLeese and W i l de r 1958; Paloheimo 1963; Cooper and Uzmann 1971 ) . A s t r o n g c o r r e l a t i o n between catch, f i s h i n g e f f o r t , and sea su r f ace temperature was repo r t ed by Dow e t a l . (1975). Lobs te r y i e l d p r e d i c t i o n s f o r Maine, based on sea su r f ace tempera- t u res , were c a l c u l a t e d by F lowers and S a i l a (1972). S a i l a and Marchessaul t (1980) d iscuss o t h e r models t h a t have been developed t o p r e d i c t t h e y i e l d o f l o b s t e r s and summarize t h e surp lus - y i e l d models t h a t have been used.

ECOLOGICAL ROLE

Feeding Hab i t s

American l o b s t e r l a r v a e have been c u l t u r e d on copepods and smal l l o b s t e r l a r v a e bu t l i t t l e i s known about t h e i r feed ing h a b i t s i n nature. Larvae were r a i s e d on a d i e t o f t h e copepods, Ac- - a r t i a , Tortanus, Eurytemora, and Pseudocalanus, and grew we1 1 on a d i e t o f smal l e r l o b s t e r l a r v a e (Templeman 1 9 3 6 ~ ) . Two l a r v a e c o l l e c t e d i n Vine- y a r d Sound, Massachusetts, con ta ined p a r t s of crustacea, diatoms, and a lgae ( H e r r i c k 1895).

Juveni 1 e and a d u l t 1 obs te r s a re omnivorous. They a re p r i m a r i l y preda- t o r s , c a t c h i n g l i v e p r e y , b u t t h e y a l s o scavenge f o r food (Ennis 1973). The b u l k o f t h e i r d i e t c o n s i s t s o f bot tom i nve r t eb ra tes , crabs, sea u rch ins , mussels, po lychaetes, p e r i - w ink les , and sea s t a r s (He r r i c k 1895, 1909; M i l l e r e t a l . 1971; Ennis 1973). F i s h and p l a n t s a l s o c o n t r i b u t e t o t h e d i e t (He r r i c k 1895; Ennis 1973). I n a r e p o r t by Ennis (1973) crabs, Cancer i r r o r a t u s and Hyas araneus, made up

0% o f t h e vo lume o f f o o d i n t h e stomachs o f l o b s t e r s c o l l e c t e d i n Bonavi s t a Bay, Newfound1 and. Sea u r - ch ins, ~ t r 6 n ~ ~ l o c e n t r o t u s droebach- i e n s i s , were t h e next most impor tan t f o o d 7 % ) .

American l o b s t e r s apparen t l y p r e f e r t o ea t crabs. The responses o f l o b s t e r s t o t h e waterborne odors o f crabs (Carc inus maenas), sea u rch ins , and mussels ( M y t i l u s e d u l i s ) demonstrate t h a t l o b s t e r s a re a t t r a c t e d by c rab odor more than t h e o the r two ( H i r t l e and Mann 1978). Lobs te rs p r e f e r rock crabs (Cancer i r r o r a t u s ) over sea u r ch ins w h e n b o t h a re present i n aquar ia (Evans and Mann 1977).

Sea u r ch ins and sea s t a r s c o n t r i b u t e a much l a r g e r p r o p o r t i o n o f t h e d i e t d u r i n g t h e m o l t i n g season t han a t o the r t imes of t h e yea r (Ennis 1 9 7 3 ) . T h i s change i n d i e t d u r i n g

m o l t i n g may be one o f s e l e c t i v i t y f o r p r e y h i g h i n c a l c i u m , an i m p o r t a n t e l ement i n hardening the exoskeleton.

The d i e t s o f female and male l o b s t e r s (47-113 mm CL) a r e s i m i l a r (Ennis 1973). Feeding a c t i v i t y d e c l i n e s i n t h e f a l l as water temperatures decrease, and remai ns low i n w i n t e r .

P reda t i on

Juveni 1 e and a d u l t American l o b s t e r s a re consumed by many bottom feed ing f i shes . A t l a n t i c cod stomachs o f t e n a r e f i l l e d w i t h j u v e n i l e 1 obs te r s ( H e r r i ck 1895). Most l o b s t e r s eaten by f i s h a re l e s s t han 50 mm CL, b u t l a r g e r l o b s t e r s a r e eaten by A t l a n t i c cod, sharks, w o l f f i s h , po l l ock , and goosef ish ( H e r r i c k 1895; Cooper and Uzmann 1980). Skates, rays, cunner, tau tog , s t r i p e d bass, b lack sea bass, sea ravens, haddock, t i 1 e f i shy conger eels, and weak f i sh sometimes p rey upon j uven i l e l o b s t e r s ( H e r r i c k 1895; Cooper and Uzmann 1977). Preda to rs 05 l o b s t e r l a r v a e have no t been i d e n t i f i e d bu t t h e p l a n k t o n i c l a r v a e p robab ly a r e consumed by sur face- feed ing p l ankt i vo rous f i s h e s .

Diseases and Pa ras i t es

Few d i s e a s e s a r e known a t t h e present t i m e which a f f e c t t h e American l o b s t e r . Gaffkemi a (Aerococcus v i r i dans var. homari ) and "she1 1 " d isease a re two b a c t e r i a1 diseases t h a t cause h i gh m o r t a l i t y i n h o l d i n g pens ( S t e w a r t 1980 ) . I n c i d e n c e o f ga f fkemia i n l o b s t e r s from n a t u r a l popu la t i ons a long t h e Maine coast averaged 7% (Vachon e t a l . 1981). Lobs te rs a l s o a re i n f e c t e d w i t h fungal d iseases and e p i b i o t i c growths. Mussels, barnacl es, mar ine a1 gae, f i 1 amentous bac te r i a , s t a l k e d protozoans, and d i atoms sometimes may compl e t e l y cover t h e exoskel e ton (He r r i c k 1909: McLeese and W i l de r 1964). A t rematode (S t i choco t l e nephropsi s) , copepod ( U n d

Acanthocephel a, and p ro tozoa (Poros- pora igantea, Anophys sp.) a r e oarasi te: o f t h e l o b s t e r (Stewart

ENVIRONMENTAL REQUIREMENTS

Temperature, s a l i n i t y , and s u b s t r a t e a r e t h e most c r i t i c a l f a c t o r s i n f l u e n c i n g 1 obs te r d i s t r i b u t i o n and abundance. A l so t h e r e i s some ev idence t h a t l o b s t e r a c t i v i t y and feed ing may be l i g h t dependent. C r i t i c a l env i ronmenta l f a c t o r s a r e d iscussed below.

Temperature

Eggs o f American l o b s t e r s ha tch a t water temperatures as low as 8°C i n no r t he rn New England (Fogar ty and Lawton 1983). A t t h e Massachusetts S t a t e Lobs te r Hatchery t h e lowest temperature a t which ha t ch ing was observed was 9.4"C (Hughes and Mat th iessen 1962). Ha tch ing u s u a l l y begins when water temperatures a re about 15°C and peaks near 20°C.

The average su r f ace water temperatures d u r i n g peak l a r v a l d e n s i t i e s i n Boothbay Harbor, Maine, range from 13.7" t o 15.0°C (Sherman and Lewis 1967). These water temperatures a r e t h e maximum f o r t h e reg ion . L a r v a l d e n s i t i e s i n Buzzards Bay, Massachusetts, peaked when t h e su r f ace water temperature was about 19°C and t h e bot tom water temperature was a b o u t 17°C (Lux e t a l . 1983 ) . Sur face water temperatures ranged f rom 10.3 t o 25.5"C when l a r v a e were c o l l e c t e d i n Cape Cod Canal, Buzzards Bay, and Cape Cod Bay, Massachusetts ( C o l l i n g s e t a l . 1983).

The development o f l a r v a e i s temperature dependent. Larvae a t t a i n e d s tage V (which marks t h e end o f t h e p e l a g i c l a r v a l pe r i od ) w i t h i n 28 days a f t e r h a t c h i n g a t a w a t e r temperature o f 19°C. Stage V was achieved i n 50 days a t 14"C, and 100 days a t 10°C (Templeman i936c) .

Lobs te r l a r v a e a r e l e s s t o l e r a n t t o low temperatures t han j u v e n i l e s o r adu l t s . I n one experiment a l l l a r v a e d i e d p r i o r t o m o l t i n g a t 5°C (Huntsman 1924).

Juveni 1 e and a d u l t American l o b s t e r s t o l e r a t e sea water tem- pe ra tu res rang ing f rom -1 t o 30.5OC (Huntsman 1924, McLeese 1956). M o l t i n g and growth cease when wate r temperatures drop below 5°C (Aiken 1980). The upper 1 e t h a l temperatures (LD i n 48 h). o f l o b s t e r s (16 t o 34. cm '?otal l e n g t h measured f rom t i p ,of ros t rum t o t i p o f t e l s o n ) acc l imated t o 27 combinat ions o f temperature (5", l o 0 , lS°C), s a l i n i t y (20, 25, 30 pp t ) , and d i sso l ved oxygen (2.9, 4.3, 6.9 m g l l ) were repo r t ed by McLeese (1956). Acc l ima t i on c o n d i t i o n s si.gni f i c a n t l y a f f e c t e d t h e upper l e t h a l temperature. Upper 1 e t h a l temperatures ranged f rom 20.6"C f o r l o b s t e r s acc l imated a t 5"C, 20 p p t s a l i n i t y , and 2.9 m g l l O 2 t o 30.5"C f o r l o b s t e r s acc l imated a t 2S°C, 30 p p t s a l i n i t y , and 6.4 mg/ l O2 (Table 3).

Changes i n water temperature s t i m u l a t e m i g r a t i o n s o f o f f s h o r e l o b s t e r s w h i c h t e n d t o seek b o t t o m water temperatures f rom 8 t o 14°C (Uzmann e t a l . 1 9 7 7 ) . D u r i n g t h e spr ing , l o b s t e r s o f f s h o r e move from t h e o u t e r Con t i nen ta l S h e l f and upper s l o p e t o s h a l l o w e r w a t e r a l o n g t h e southern New England Con t i nen ta l S h e l f , i n c l u d i n g Georges Bank and t h e coas ta l wa te rs o f New York, Rhode I s 1 and, and southern Massachusetts. It i s p o s s i b l e t h a t bot tom water temperatures (8 t o 14°C) i n t h e sha l lower waters a r e more s u i t a b l e f o r t h e e x t r u s i o n o f eggs, m o l t i n g , and mat ing than a r e t h e summer bot tom temperatures over t h e o u t e r Con t i nen- t a l Shel f and upper s l ope (Cooper and Uzmann 1971). Re tu rn l o b s t e r m i g r a t i o n s t o t h e o u t e r s h e l f and upper s l ope waters beg in i n l a t e summer and con t i nue th rough November as i n s h o r e bot tom water temperatures drop. By December t h e l o b s t e r s o f f s h o r e have re tu rned t o t h e o u t e r

Table 3. Upper l e t h a l temperatures and lower l e t h a l s a l i n i t y and oxygen concent ra t ions f o r American l o b s t e r s acc l imated t o 27 combinat ions o f tem- peratu re , sa l i n i t y , and oxygen (McLeese 1956).

Lower Lower Acc l imat ion c o n d i t i o n s Upper l e t h a l l e t h a l

Temperature Sal i n i t y Oxygen l e t h a l s a l i n i t y oxygen ("C) ( P P ~ ) (mg/l) temp. ( P P ~ ) (mg/l)

s h e l f and u p p e r s l o p e w a t e r s where bot tom temperatures a r e 8 t o 12OC (Uzmann e t a l . 1977).

S a l i n i t y

S tud ies of American l o b s t e r l a r v a e exposed t o va r i ous s a l i n i t i e s i n wate r temperatures o f 15.0 t o 17.5OC, revea l ed t h a t s u r v i v a l was h i ghes t a t a s a l i n i t y o f 30 p p t and s a l i n i t i e s as low as 21 pp t were o n l y s l i g h t l y l e s s s u i t a b l e (Templeman 1936). S u r v i v a l o f l a r v a e t o s tage I V decreased as sa l i n i t i e s dropped below 21 ppt , and no l a r v a e su rv i ved l e s s than 17.0 ppt . Larvae at tempted t o avo id s a l i n i t i e s as low as 21.4 p p t a t wa te r temperatures near 22OC ( S c a r r a t t and Raine 1967). There i s no i n f o r m a t i o n on s u r v i v a l r a t e s o f l o b s t e r s a t unusua l l y h i gh s a l i n i t i e s .

The lower l e t h a l s a l i n i t y l e v e l s (LD+O i n 48 h o u r s ) o f j u v e n i l e and adu t l o b s t e r s acc l imated t o 27

. combinat ions o f s a l i n i t y , d i sso l ved oxygen, and wate r temperature were r e p o r t e d by McLeese (1956 ) . Lower l e t h a l s a l i n i t i e s ranged f rom 6 pp t f o r l o b s t e r s acc l imated a t 5OC, 6.4 m g l l 02, and 30 p p t s a l i n i t y t o 16.4 pp t f o r l o b s t e r s acc l imated a t 25OC, 6.4 mg/ l 02, and 30 p p t s a l i n i t y (Table 3). Due t o osmoregulatory s t r e s s , m o l t i n g l o b s t e r s a r e l e s s r e s i s t a n t t o low s a l i n i t i e s t han ha rd - she l l ed l o b s t e r s .

D isso lved Oxygen

American l o b s t e r s can s u r v i v e re1 a t i v e l y low d i s s o l v e d oxygen concent r a t i o n s . McLeese (1956) r epo r t ed t h a t t h e lower l e t h a l oxygen concen t ra t i on was 0.2 m g l l f o r l o b s t e r s acc l imated a t 5OC and 30 pp t s a l i n i t y and rose t o 1.7 m g l l a t a c c l i m a t i o n c o n d i t i o n s o f 25OC and 20 p p t s a l i n i t y (Tab le 3) . Acc l ima t i on 1 eve1 s of temperature and s a l i n i t y s i g n i f i c a n t l y a f f e c t e d t h e lower l e t h a l oxygen concen t ra t i on whereas a c c l i m a t i o n l e v e l o f oxygen d i d n o t have a s i gn i f i cant e f f h c t (McLeese 1956).

Subs t ra te

J u v e n i l e and a d u l t American l ob - s t e r s occupy subs t ra tes cha rac te r i zed by sand-rock, bedrock-rock, mud-rock, mud -s i l t , and c l a y - s i l t (Thomas 1968; Cobb 1971; Cooper e t a l . 1975; Cooper and Uzmann 1980 ) . The most common s u b s t r a t e occupied by i nsho re 1 obs te rs i s sand w i t h o v e r l y i n g boulders. T h i s s u b s t r a t e i s uncommon i n o f fshore areas where i t i s u s u a l l y r e s t r i c t e d t o t h e heads o f submarine canyons (Cooper and Uzmann 1980). The most common subs t ra tes i n o f f s h o r e areas a r e mud o r c l a y w i t h o v e r l y i n g s i l t . Lobs te r s burrow o r excavate bowlshaped depress ions i n t o these s o f t subs t ra tes f o r cover and p r o t e c t i o n (Cooper and Uzmann 1980).

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Dunham, P.J., and D. Skinner-Jacobs. 1978. I n t e r m o l t m a t i n q i n t h e l o b s t e r (Homarus amehcanus) . Mar. Behav. Phys io l . 5:209-214.

Ennis, G.P. 1972. Growth per moult o f tagged l o b s t e r s (~omarus ameri- canus) i n Bonavis ta Bay. New- f o u n d l and. J. F i s h . ~ e s . . Boa rd Can. 29: 143-148.

Ennis, G.P. 1973. Food, feed ing and c o n d i t i o n o f l o b s t e r , Homarus americanus, throughout t h e sea- sonal c y c l e i n Bonav is ta Bay, New- foundland. J. F ish. Res. Board. Can. 30: 1905-1909.

Enn i s , G.P. 1975. O b s e r v a t i o n s on h a t c h i n g and 1 a r v a l r e l e a s e i n t h e l o b s t e r Homarus ameri canus. J . F ish. Res. Board Can.

Ennis, G.P. 1983. Annual v a r i a t i o n s i n s tand ing stock i n a New- foundl and popu la t i on o f l obs te rs . N. Am. J. F ish. Manage. 3:26-33.

Ennis, G.P., P.M. C o l l i n s , and G. Dawe. 1982. F i she r i es and popu la t i on b i o l o g y o f l o b s t e r s . . (Homarus americanus) a t Comfort ' Cove. Newfound1 and. Can. Tech. Rep. . ~ i sh. Aquat. Sc i . 1116.

Evans, P.D., and K.H. Mann. 1977. S e l e c t i o n o f prey by American l o b s t e r , Homarus americanus, when o f f e r e d a choice between sea u r - c h i n s and c rabs . J . F i s h . Res. Board Can. 34: 2203-2207.

Farmer, A .S. 1974. Reproduct ion i n norve i cus (Decapoda :

! % ~ : , ~ f d , e h . London 174:

Flowers, J.M., and S.B. S a i l a . 1972. An ana l ys i s o f temperature e f f e c t s on t h e i n s h o r e l o b s t e r f i s h e r y . J . F ish . Res. Board Can. 29:1221-1225.

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Hughes, J.T., and G.C. Mat th iessen. 1962. Observat ions on t h e b i o l o g y o f t h e American l o b s t e r , ~ o m a r i s americanus. Limn01 . Oceanogr. 7:314-321.

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Krouse, J.S. 1973. M a t u r i t y , sex r a t i o , and s i z e c o m p o s i t i o n o f t h e n a t u r a l popu la t i on o f Ameri- . . can l o b s t e r , Homarus americanus, a long t h e Maine coast . U.S. ~ a t l : Mar. F ish . Serv. F ish . B u l l . 71: 165-173.

Lux, F.E., G.F. K e l l y , and C.L. Wheeler. 1983. D i s t r i b u t i o n and abundance o f 1 a r va l l o b s t e r s (Homarus americanus) i n Buzzards Bay, Massachusetts, d u r i n g 1 9 7 6 - 79. NOAA Tech. Rep., N a t l . Mar. F i sh . Serv., SSRF-775: 29-33.

McLeese, D.W. 1956. E f f e c t s of tem- pera tu re , s a l i n i t y , and oxygen on t h e s u r v i v a l o f t h e American l o b s t e r . J . F i sh . Res. Board Can. 13: 247-272.

McLeese, D.W. 1970. De tec t i on o f d i s - so lved substances by t h e American l o b s t e r (Homarus ameri canus) and 01 f a c t o r y a t t r a c t i o n between lobsters". J. F i sh . Res. Board Can. 27:1371-1378.

McLeese, D.W., R.L. Spraggins, A.K. Base, and B.N. Praman ik . 1977. Chemical and behav io ra l s t u d i e s o f t h e sex a t t r a c t i o n o f t h e l o b s t e r (Homarus americanus). Mar. Behav . P h y s i o l . 4: 219-232.

McLeese, D.W., and D.G. Wi lder . 1958. The a c t i v i t y and ca tchab i 1 i t v o f t h e l o b s t e r (Homarus americ&us) i n r e l a t i o n t o t e m ~ e r a t u r e . 5. Fish. Res. Board Can. B u l l . 147: 1-69.

McLeese, D.W., and D.G. Wi lder . 1964. Lobs te r s to rage and shipment. F ish . Res. Board Can., B u l l . 147: 1-69.

McRae, E. D. 1960. Lobs te r exp lo ra - t i o n s on c o n t i n e n t a l s h e l f and s lope o f f no r t heas t coas t o f t h e Un i t ed States. Commer. F ish . Rev. 9(22):1-7.

M i l l e r , R.J., K.H. Mann, and D.J. S c a r r a t t . 1971. Produc t ion po- t e n t i a l o f a seaweed-lobster community i n eas te rn Canada. J. F ish . Res. Board Can. 28:1733-1738.

Paloheimo, J.E. 1963. E s t i m a t i o n o f catchabi 1 i t i e s and p o p u l a t i o n s i zes of l o b s t e r s . J. F ish . Res. Board Can. 20: 59-88.

management o f l o b s t e r s , Vol. I. Academic Press, New York.

P h i l l i p s , B.F., and A.N. Sast ry . 1980. L a r v a l ecology. Pages 11-57 i n J.S. Cobb and B.F. P h i l l i p s , e d C The b i o l o g y and management o f l o b s t e r s , Vol . 11. Academic Press, New York.

Sa i la , S.B., J.M. Flowers, and J.T. Hughes. 1969. Fecund i ty and t h e American l o b s t e r , Homarus ameri- canus. Trans. Am. F ish . S o c x : 537-539.

S a i l a , S.B., and G. Marchessaul t . 1980. Popu la t i on dynamics o f c l awed l o b s t e r s . Pages 219-241 i n J.S. Cobb and B.F. P h i l l i p s , - eds. The b i o l o g y and management o f l o b s t e r s , Vol . 1 1 . Academic Press, New York.

S c a r r a t t , D.J. 1964. Abundance and d i s t r i b u t i o n o f l o b s t e r l a r v a e (Homarus ameri canus) i n Nor th - umberland S t r a i t . J. F ish . Res. Board Can. 21:661-680.

S c a r r a t t , D .J. 1973. Abundance, su r - v i v a l and v e r t i c a l and d i u r n a l d i s t r i b u t i o n o f l o b s t e r l a r v a e i n Northumberl and S t r a i t , 1962-63, and t h e i r r e l a t i o n s h i p s w i t h commercial s tocks. J. F ish . Res. Board Can. 30: 1819-1824.

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50272 - 1 0 1

.- -. - I 8. Perform~ng Organization Rept. No.

I REPORT DOCUMENTATION i ' L R E ~ ~ ~ 2.

Biol. Rep. 82(11.33) * 1 Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic) -- American

3. Recap~ent's Accession NO.

5. Report Date

April 1985 6.

Maine Cooperative Fi shery Research Uni t 313 Murray Hal 1 University of Maine Orono, Maine 04469

9. Performing Organization Name and Address

11. Contract(C) or Grant(G) No.

(C)

(G)

10. PmiectlTasklWork Unit No.

12. Sponsoring Organization Name and Address

National Coastal Ecosystems Team U.S. Army Corps of Engineers

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

13. Type of Report 6 Per~od Covered

Fish and Wildlife Service Waterways Experiment Station U.S. Dep. of the Interior P.O. Box 631 Washington, DC 20240 --

Vicksburg, MS 39180

16. Abstract (Limit: 200 words)

-- -- 14.

Species profiles are 1 i tera ture summaries of the taxonomy, morphology, distr ibution, 1 i f e hi story, and environmental requirements of coastal aquatic species. They are designed to ass i s t in environmental impact assessment. The American 1 obster (Homarus americanus) i s a valuable commercial shellfish. After spawning, lobsters undergo a series of molts; as adults they l ive in coastal and offshore waters. Lobsters are captured in baited traps and incidentally in trawls. About 5-6 million pounds were captured commercially in 1983, a downward trend from 1971. Major environmental factors affecting reproduction, growth, and survival are water temperature, oxygen concentration, sal ini ty , and substrate.

15. Supplementary Notes

17. Document Analysis a. Descriptors I Lobsters Growth Feedi ng

American lobster Homarus ameri canus Sal i ni ty requi rements

Temperature requ i rements Spawni ng

I Unlimited

c. COSATI Field/Grouo

20. Security Class (This Page) C 18. Ava~lability Statement 1 19. Securoty Class (This Report)

I I (See ANSI-239.18) OPTIONAL FORM 272 (4-77)

(Formerly NTIS-35)

21. No. of Pages

Department of Commerce

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