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 
This is one of the first reports to be published in the new "Biological 

Report" series. This technical report series, pub1 i shed by the Research 

and Development branch of the U.S. Fish and Wildlife Service, replaces 

the "FWS/OBS1' series published from 1976 to September 1984. The Biological Report series is designed for the rapid publication of reports with 

an application orientation, and it continues the focus of the FWS/OBS 

series on resource management i ssues and f i sh and wi ldl i fe needs. 
Bi 01 ogi cal Report 82(11.33) 

TR EL-82-4 

Apri 1 1985 

Species Prof i 1 es: Life Hi stories and Environmental Requirements 

of Coastal Fishes and Invertebrates (North Atlantic) 

AMERICAN LOBSTER 

Chet MacKenzie 

and John R. Moring 

Maine Cooperative Fishery Research Unit 

Department of Zoology 

313 Murray Hall 

University of Maine 

Orono, ME 04469 

Project Manager 

Larry Shanks 

Project Officer 

John Parsons 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

1010 Gause Boulevard 

Slidell, LA 70458 

Performed for 

Coastal Ecol ogy Group 

U.S. Army Corps of Engineers 

Waterways Experiment Station 

Vicksburg, MS 39180 

and 

National Coastal Ecosystems Team 

Division of Biological Services 

Research and Development 

Fish and Wildlife Service 

U.S. Department of the Interior 

Washington, DC 20240 
This series should be referenced as follows: 

U.S. Fish and Wildlife Service. 1983-19-. Species profiles: life histories 

and environmental requirements of coastal fishes and invertebrates. U. S. Fish 

Wildl. Serv. Biol. Rep. 82(11). U.S. Army Corps of Engineers, TR EL-82-4. 

This profile should be cited as follows: 

MacKenzie, C., and J.R. Moring. 1985. Species profiles: life histories and 

environmental requirements of coastal fishes and invertebrates (North At1 antic) 

--American lobster. U.S. Fish Wildl. Serv. Biol. Rep. 82(11.33). U.S. Army 

Corps of Engineers, TR EL-82-4. 19 PP. 
PREFACE 

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

principally fish, of sport, cornmerci a1 , or ecological importance. The profil es 

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

comprehensive sketch of the biological characteristics and environmental requirements of the species and to describe how populations of the species may be 

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

profile has sections on taxonomy, 1 ife history, ecol ogical role, envi ronmental 

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

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

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

the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to one 

of the following addresses. 

Information Transfer Special ist 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

NASA-Sl idel 1 Computer Compl ex 

1010 Gause Boul evard 

Sl idel 1 , LA 70458 

U.S. Army Engineer Waterways Experiment Station 

Attention: WESER-C 

Post Office Box 631 

Vicksburg, MS 39180 
CONVERSION TABLE 

Metric to U.S. Customary 

Mu1 tiply ' !?Y To Obtain 

mil 1 imeters (m) 

centimeters (an) 

meters (m) 

ki 1 meters ( km) 

2 

square meters (m ) 10.76 

square ki 1 meters ( km2) 0.3861 

hectares (ha) 2.471 

liters (1) 

cubic meters (m3) 

cubic meters 

inches 

inches 

feet 

mil es 

square feet 

square miles 

acres 

gal 1 ons 

cubic feet 

acre- feet 

mill igrams (mg) 0.00003527 ounces 

grams (g) 0.03527 ounces 

kilograms (kg) 2.205 pounds 

metric tons (t) 2205.0 pounds 

metric tons 1.102 short tons 

ki 1 ocal ories ( kcal ) 3.968 British thermal units 

Celsius degrees 1.8(C0) + 32 Fahrenheit degrees 

U.S. Customary to Metric 

inches 25.40 

inches 2.54 

feet (f t) 0.3048 

fa thorns 1.829 

miles (mi) 1.609 

nautical miles (mi) 1.852 

square feet (ft2) 

acres 2 

square miles (mi ) 

gal 1 ons ( gal ) 3.785 

cubic feet (ft3) 0.02831 

acre- feet 1233.0 

ounces (02) 28.35 

pounds (Ib) 0.4536 

short tons (ton) 0.9072 

British thermal units (Btu) 0.2520 

mil 1 imeters 

centimeters 

meters 

meters 

kil ometers 

ki 1 ometers 

square meters 

hectares 

square kil ometers 

1 i ters 

cubic meters 

cubic meters 

grams 

ki 1 og rams 

metric tons 

ki 1 ocal ori es 

Fahrenheit degrees 0.5556(F0 - 32) Celsius degrees 
CONTENTS 

Page 

PREFACE ................................. i ii 

CONVERSION TABLE ............................ i v 

ACKNOWLEDGMENTS ............................. v i 

NOMENCLATURE/TAXONOMY/RANGE ....................... 1 

MORPHOLOGY/IDENTIFICATION AIDS ..................... 2 

REASON FOR INCLUSION IN SERlES ..................... 2 

LIFE HISTORY .............................. 2 

Spawning ............................... 2 

EggsandFecundity .......................... 3 

Prelarvae and Larvae ......................... 4 

Juveniles and Adults ......................... 5 

MOLTING AND GROWTH CHARACTERISTICS ................... 5 

FISHERY ................................. 6 

Maine ................................. 7 

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

Massachusetts ............................. 8 

POPULATIONDYNAMICS ........................... 9 

ECOLOGICAL ROLE ............................. 10 

Feeding Habits ............................ 10 

Predation ............................... 10 

Diseases and Parasites ........................ 10 

ENVIRONMENTAL REQUIREMENTS ....................... 11 

Temperature .............................. 11 

Salinity ............................... 13 

DissolvedOxygen ........................... 13 

Substrate ............................... 13 

LITERATURECITED ............................ 15 
ACKNOWLEDGMENTS 

For reviewing this manuscript, the authors thank Robert C. Bayer, Professor 

of Animal and Veterinary Sciences, University of Maine at Orono, and Robert S. 

Steneck, Research Assistant Professor in Zoology, Ira Darl ing Center, Walpole, 

Mai ne. 
Fi gure 1. Ameri can lobster, Homarus ameri canus. -- 

AMERICAN LOBSTER 

NOMENCLATURE /TAXONOMY /RANGE 

Scientific name.... Homarus americanus 

Preferred common name ........ American 

lobster (Figure 1). 

Other cornmon names .......... lobster, 

Maine lobster, northern lobster, 

blueshells (color variant), hard 

shell lobster, old shell lobster; 

blackshell, crack backer (lobsters 

preparing to molt); shedder, soft 

shell, new shell, shadow, rubber 

shell, paper shell, and buckle 

she1 1 (recently molted lobsters) 

(Herri ck 1895). 

Class ...................... Crustacea 

Order ........................ Oecapoda 

Family .................... Nephropidae 

Geographi c range: American 1 obsters 

inhabit the coastal and oceanic 

waters of the Atlantic Ocean from 

Labrador south to North Carolina 

(Herrick 1909). They live from 

the intertidal zone out to a depth 

of 720 meters (McRae 1960). Major 

coastal concentrations of lobster 

are in the Gulf of Maine and the 

coastal waters of New Brunswick 

and Nova Scotia, Canada (Cooper 

and Uzmann 1980). American 

lobsters are widely distributed in 

most of the coastal waters of the 

northeastern United States. Major 

offshore concentrations are along 

the outer edge of the Continental 

Shelf and upper slope between the 

eastern part of Georges Bank and 
the offing of Delaware Bay 

(Schroeder 1959). Small numbers 

inhabit the outer edge of the Nova 

Scotian shelf (Cooper and Uzmann 

1980). 

MORPHOLOGY /IDENTIFICATION AIDS 

The American lobster has five 

cephal ic and eight thoracic segments 

fused together to form a 

cephalothorax, which is covered by a 

shield-1 i ke carapace (Figure 1). All 

the segments comprising the 

cephal ot horax bear appendages. 

Beginning anteriorly, the appendages 

of the cephalothorax are the first 

antennae, second antennae, mandibles, 

first maxi 11 ae, second maxi 11 ae, 

first, second, and third maxillipeds 

and five pairs of walking legs, or 

pereiopods (Phillips et al. 1980). The 

first three pairs of pereiopods are 

chelate, the first pair modified into 

. large claws. Oneclaw of this pair, 

the crusher, is larger than the other 

claw, the cutter. American 1 obsters 

have compound eyes that are movable 

and stalked. 

The six body segments posterior 

of the carapace make up the abdomen. 

Pai red, bi ramous pl eopods are 1 ocated 

on the first five abdominal segments. 

The last abdominal segment consists of 

the tel son flanked by uropods, which 

are modified pleopods. The broad tail 

fin, composed of the tel son and uropods, is used for backward swimming, 

which is characteristic of lobsters. 

The first pair of pleopods on 

male lobsters are modified into rigid 

structures, gonapods, which are used 

to convey sperm to the female (Cobb 

1976). In females, the first pair of 

pleopods are similar to the others but 

are much smaller. There are two 

characteristics used to separate the 

sexes of mature lobsters. Males have 

sharp spines under the abdomen; female 

spines are blunt. The male's abdomen 

is narrower than the width of the 

carapace; those in the female are 

about equal (Cobb 1976). 

American lobsters are normally 

greeni sh-brown but some specimens are 

blue, red, reddi sh-ye1 low, cream, 

black, or calico (Herrick 1895). 

The largest American lobsters are 

males (Wolfe 1978). The largest male 

on record weighed 19.25 kg, and was 

63.4 cm long. The heaviest female 

weighed 8.35 kg (Aiken 1980). 

The total propodite length in 

relation to carapace length is a means 

of distinguishing between the 1 arval 

stages of the American lobster and the 

~uropean 1 obster, Homarus gammarus 

(Gruffydd et al. 19t5).The total 

propodite length is greater than the 

carapace length of the European 

lobster larvae. The opposite is true 

for American lobster larvae. 

Geographic isolation is the only 

character that distinguishes the 

adults of the two species (Corrivault 

and Tremblay 1948; as cited in 

Gruffydd et a1 . 1975). 

REASON FOR INCLUSION IN SERIES 

Ameri can 1 obsters support an 

important commerci a1 fishery along the 

northeastern coast of the U.S. They 

are abundant in coastal and offshore 

waters. It is important that the 

impact of development projects on 

lobster populations be considered so 

that this important and valuable 

natural resource will be protected. 

LIFE HISTORY 

Spawni nq 

Male American lobsters mature at 

shorter lengths than females. Most 

ma1 es carry viable spermatozoa when 

the carapace 1 ength (CL) (measured 

from tip of rostrum to the back of the 

carapace) is 40 to 45 mm. About 50% 

of the males examined along the Maine 
coast were physiologically mature at 

44 mm CL: the smallest mature male was 

41 mm CL (Krouse 1973). Females in 

Maine mature when they are about 90 mm 

CL (Krouse 1973) but in warmer waters 

(Long Island Sound), most mature 

at lenqths of 70 to 74 mm CL 

(~em~leian 1936b; Bri ggs and Mushacke 

1979). 

Small males usually cannot mate 

successful ly with 1 arger f ma1 es 

(Templeman 1934, 1935). Males may be 

capable of producing mature spermatozoa when they are 40-45 mm CL but 

they may not be capable of mating 

until they are as large as the 

smal lest mature females. 

When spawning, lobsters pair for 

about 2 weeks (Atema et al. 1979). 

Femal es 1 eave thei r sol i tary she1 ters 

about 7 days before molting and share 

the shelter of a dominant, territori a1 

ma1 e. 

A female sex pheromone is produced before or at the time of 

molting . Thi s pheromone suppresses 

ma1 e aggression and induces courtship 

(McLeese 1970; Atema and Engstrom 

1971). Pre-mol t behavi oral di spl ays 

are also important in successful pair 

formation (Atema et al. 1979). Mating 

usually takes place 20-40 minutes 

after the female molts, but to be 

successful , mating must take place 

within a few hours (rarely more than 

one) after the female has molted. One 

female, however, was reported to have 

successfully mated 12 days after 

molting (Templ eman 1936a). Successful 

mating of hard shelled female lobsters 

several months after molting has been 

reported (Dunham and Ski nner-Jacohs 

1978; Aiken and Waddy 1980a). 

The male mounts the female and 

turns her over with his walking legs 

and maxi 11 ipeds. The male places his 

gonapods in the female seminal receptacl e (thelycum) and deposits a 

spermatophore (Herri ck 1895; Hughes 

and Matthiessen 1962; Atema et al. 

1979). Mating usually is completed in 

ahout 30 seconds; the longest in 3 

minutes (Atema et al. 1979). Males 

larger than the female are most successful at copulati on (Templeman 1934, 

1935). Males protect females from 

predation and cannibalism for up to 7 

days during the vulnerable post-mol t 

stage. This "protection" by the male 

also ensures that other males wi 11 not 

copulate with his mate (Atema et al. 

1979). 

Eggs are normally extruded 11 to 

13 months after mating. As ova are 

released, they are fertilized by part 

of the spermatozoa stored in the 

seminal receptacle (Templ eman 1936a: 

Krouse 1973). Oviposi tion occurs on a 

two year cycle even if the female is 

not carrying spermatozoa. Evidence is 

strong that eggs are ferti 1 i zed 

externally as they pass over the seminal receptacle (Aiken and Waddy 

1980a), but Farmer (1974) be1 i eves 

that fertilization is internal. 

Females are capable of fertilizing at least two successive batches of 

eggs from a single mating (Templeman 

1936a; Aiken and Waddy 1980a; Campbell 

1983). Large females do not molt or 

mate every year. 

Eggs and Fecundity 

Freshly extruded American lobster 

eggs are dark green and irregularly 

shaped. They soon become spherical 

and telolecithal, and are about 1.5 to 

1.7 mm in di ameter (Herrick 1909). As 

eggs develop, they increase in size 

and become elongated and lighter in 

color. 

The number of eggs in a clutch 

ranges from 3,000 to 115,000 (Herrick 

1909; Saila et a?. 1969; Perkins 

1971). The 1 ogari thmi c re1 ationshi p 

between average fecundity (Y) and 

carapace length (CL) of lobsters 

collected from inshore waters off 

Rhode Is1 and and Massachusetts (Sai 1 a 

et al. 1969) is: 

loglO Y = -1.6017 + 2.8647 loglo CL. 
The estimated fecundi ty-1 ength (CL) 

relationship of lobsters from the 

Continental She1 f off southern New 

England is: In Y = -5.0231 + 3.1569 In 

CL (Perkins 1971). Individual 

variation in fecundity is large 

(Squi res 1970). 

After extrusion, fertilized eggs 

become firmly attached to pleopods, 

where they develop for 9-11 months 

(Aiken and Waddy 1980a). About 36% of 

the eggs are lost between extrusion 

and hatching (Perkins 1971). Temperature is a key factor that 

determines the length of time the eggs 

are carried on the pleopods (Templeman 

1940; Aiken and Waddy 1980b). Eggs 

develop to the 16 cell stage in two 

days at 18.5OC, and 4.8 days at 10.5OC 

(Temp1 eman 1940). 

Lobster eggs hatch from May to 

October; the warmer the water the 

earlier the hatch. In Massachusetts, 

eggs begin hatching in mid or late May 

when water temperatures are about 15OC 

(Hughes and Matthiessen 1962). Peak 

hatching is in June and early July 

when water temperatures reach 20°C. 

The time requ'ired to hatch all the 

eggs within a brood depends on the 

wat~r temperature. All eggs within a 

brood usually hatch in 2 to 3 days at 

20°C, and in 10-14 days at 15OC 

(Hughes and Matthiessen 1962). 

Females release larvae during a 

brief period at night by actively 

beating their pl eopods (Enni s 1975). 

Females normally molt and mate within 

one month after their brood has hatched. 

Prel arvae and Larvae 

American lobsters pass through 

one prel arval and four free-swimmi ng 

larval stages before settling to the 

bottom and molting into juveniles. 

Most prel arvae molt into the fi rst 

larval stage before being released by 

females (Davis 1964). All larval 

stages are normally completed in 25-35 

days, but the length of time is 

temperature dependent (Tab1 e 1). 

Herrick (1895, 1909) describes and 

diagrams each of the four larval 

stages. 

The distribution and abundance of 

1 arvae are affected by the di stri bution of spawning females, surface 

current velocity and direction, temperature, salinity, light intensity, 

hydrostatic pressure, and 1 arval 

mortal i ty (Phi 11 ips and Sastry 1980). 

The larvae are planktonic from late 

May to October; they appear earlier in 

the plankton in southern New England 

than in the Gulf of Maine (Fogarty and 

Lawton 1983). Stage I larvae were 

collected from May to early July in 

Block Island Sound off Rhode Island 

(Bibb et al. 1983) and from June to 

early August off the coast of Maine 

(Sherman and Lewis 1967). 

Vertical distribution is affected 

by 1 ight intensity (Templeman 1937, 

Scarratt 1973, Harding et al. 1982). 

At night the larvae seek deeper waters 

but return near the surface during day 

(Phillips and Sastry 1980). Phototactic responses observed in the 

laboratory differed among 1 arval 

stages and within each larval stage 

(Hadley 1905, 1908). Stage I and IV 

1 arvae were originally positively 

photot act ic but became negat i vely 

Table 1. The approximate number of 

days required by larvae to pass 

through each larval stage at different 

temperatures (modified fro,n data by 

Templeman 1936a in Aiken 1980). 

- 

Temp. Larval stage 

(OC) 1 -- 2 3 4 Total 

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 -- 
phototactic late in each stage. Stage 

I1 and I11 larvae were negatively 

phototactic but responses were highly 

vari able. 

High larval densities along 

windward coasts suggest that larvae 

are transported by surface currents 

(Fogarty 1983). Prevai 1 ing southwesterly winds along the New England 

coast in the summer may transport 

larvae from offshore to coastal waters 

(Fogarty 1983). 

Late in stage IV, larvae settle 

to the bottom and burrow into the 

substrate. They molt into juveniles 

while sheltered in their burrows 

(Cooper and Uzmann 1980). 

Juveniles and Adults 

American lobsters in inshore 

waters excavate shelters under objects 

resting on the sea floor when there 

are no natural crevices available as 

shel ter. Highest lobster densities 

are on sand substrate with overlying 

flattened rocks. Juveni 1 e and adult 

1 obsters are negatively phototactic 

and prefer dark shelters shaped so 

that the lobster can maintain contact 

with the roof and walls (Cobb 1971). 

Lobsters inshore tend to be 

solitary. They rarely share shelters, 

and sharing behavior has only been 

reported in winter when bottom water 

temperatures are coldest (Cooper and 

Uzmann 1980). Lobsters offshore often 

share shelters or bowl-shaped 

-depressions in the substrate. This 

behavior may be caused by the scarcity' 

of shelters (Cooper and Uzmann 1980). 

Juvenile American lobsters less 

than 35 mm CL rarely leave their 

shel ters (Cooper and Uzmann 1977). 

When juveniles are 35-40 mn CL they 

Lenture just outside their shelters at 

night. When about 45 m CL they begin 

nocturnal foraging away from thei r 

shelters. Adult and juvenile lobsters 

usually travel less than 300 m from 

the home shelter when foraging (Cooper 

and Uzmann 1980). 

Lobsters inshore move from shoal 

water (< 10 m) to deeper water when 

storms generate heavy seas (Cooper et 

a1 . 1975). These horizontal movements 

are usually 100 m or less but involve 

an increase in depth up to 10 m. 

Lobsters a1 ong the Canadian east coast 

make short distance seasonal movements 

from re1 atively deep waters (15-18 m) 

in winter to shallower waters (7-9 m) 

in summer (Stasko 1980). 

Lobsters inshore appear to have a 

limited home range. About 99% of the 

lobsters (81-123 mm CL) recaptured 

after tagging were within 2.2 km from 

the release site (Cooper 1970). From 

74% to 98% of the lobsters (81-116 mn 

CL) recaptured after being released at 

sites along the coast of Maine were 

caught within 8 km from the release 

site (Krouse 1973). 

In another study 22% of the large 

mature lobsters (127-200 mm CL) that 

were recaptured after being tagged and 

released in Penobscot Bay, Maine, were 

caught 137 km to 256 km from their 

release points (Dow 1974). Large 

lobsters apparently migrate farther 

than small 1 obsters. 

Lobsters offshore migrate greater 

di stances than thei r coastal counterparts. Movements of up to 345 km in 

71 days were reported by Uzmann et al. 

(1977). Ground speeds ranged from 

0.18 to 10.2 km per day; the median 

was 1.7 km. 

MOLTING AND GROWTH CHARACTERISTICS 

The growth of lobsters is continuous, but it is greatest when they 

molt (Phi 1 lips et a1 . 1980). The 

growth rate depends on the molting 

frequency and the size increase at 

molting. With increasing age, 

Ameri can 1 obsters molt 1 ess frequently 

and grow proportional ly 1 ess at each 

molt. Lobsters molt an average of 10 
,times in their first year, 3 or 4 

times in the second and third years, 

twice in the fourth year, and once a 

year or less thereafter (Hughes and 

Matthiessen 1962). 

Although salinity, dissolved 

oxygen, food avai labi 1 ity, and 

crowding are factors that affect 

growth (Phil 1 ips et al. 1980), 

temperature appears to be the dominant 

factor (Huntsman 1924; Temp1 eman 

1936c; Hughes and Matthi essen 1962; 

Hughes et al. 1972; Gruffydd et al. 

1975). For example, captive juveniles 

held two years in water with a 

constant temperature about 23°C 

weighed 454 g but those kept at 

ambient temperatures (2" to 24°C) took 

5.5 years to reach the same weight 

(Hughes et a1 . 1972). The higher 

growth rate was due to a greater 

number of molts, not to a change in 

the rate of growth between molts. 

The percentage increase in length 

per molt of larval lobsters collected 

in the Northumberland Strait, southern 

Gulf of St. Lawrence, was 33% from 

larval stage I to stage 11, 32% from 

stage I1 to stage 111, and 30% from 

stage I11 to stage IV (Wilder 1953). 

Estimates of the average 

percentage increase in length per molt 

for juveni les and adults ranged from 

7% to 20%; weight gains were 30% to 

61% (Aiken 1980). Mature females have 

a slower growth rate than males 

because femal es molt 1 ess frequently . Growth between molts for the two sexes 

is similar (Wilder 1953). Other 

studies have indicated that the 

percentage increase in lengths of 

mature females between molts is less 

than that of mature males of the same 

size (Wilder 1963; Cooper and Uzmann 

1971; Ennis 1972; Campbell 1983). 

Lobsters offshore (90 mm CL) grow 

faster (18% length increase) per molt 

(Cooper 1970) than 1 obsters inshore 

(12%) that are the same size. The 

difference in growth of the two sexes 

is slight (2%) according to Cooper and 

Uzmann (1971). Lobsters offshore molt 

more often than lobsters inshore. The 

difference in growth rates of inshore 

and offshore 1 obsters may be explained 

by the migratory habits of the two 

populations. Each year offshore 

lobsters migrate between the outer 

Continental Shelf and upper slope 

waters (8" to 12°C) and shallower 

Continental Shelf waters (10" to 

17.5"C) seeking optimum water 

temperatures for growth, molting, and 

extrusion of eggs (Cooper and Uzmann 

1971, Uzmann et al. 1977) whereas 

inshore lobsters are nonmigratory and 

subject to winter temperatures (<5"C) 

that inhi bit growth. 

The average increase in length 

for lobsters (68-110 mm CL) captured, 

released, and recaptured four to 

twelve months later along the Canadian 

east coast was 13% to 15% with an 

average weight increase of 43% to 54% 

(Wi 1 der 1953). The average increase 

in length per molt for lobsters 

(20-176 mm CL) along the Maine coast 

was 8% (Thomas 1973). He found that 

the length relationship between 

prernolt and postmolt for lobsters 

ranging in premolt sizes from 20 to 

176 mm CL was 1 inear. 

Cooper and Uzmann (1980) determined the average growth increment per 

year for lobsters offshore that molt, 

and the annual probability of molting. 

FISHERY 

American 1 obsters have been harvested commercially since the 18th 

century. In the mid-19th century, the 

first 1 arge scale exploitation of lobster resources was induced by the 

canning industry (Dow 1980). By the 

end of the 19th century, the majority 

of lobsters were being sold to the' 

live lobster industry. Storage faci lities (or pounds) were constructed to 

hold live lobsters so that markets 

could be regularly supplied. Canada 

and the United States together have 
about 75 storage facilities with an 

estimated capacity of 75 mi 1 lion lobsters (Dow 1980). 

T r a d i t i o n a l l y , l o b s t e r s are 

caught in baited traps (pots). Most 

lobsters are caught in shallow (5-30m) 

inshore waters (Cobb 1976). 

Landings from the offshore 

fishing grounds (along the outer edge 

of the Continental Shelf and the upper 

slope from Georges Bank to Chesapeake 

Bay at depths from lOOm to 600m) 

increased sharply from about 800,000 

lb in 1958 to nearly 9 million 1b in 

1970 (Figure 2). Offshore lobster 

1 andi ngs have declined since 1971 to 

about 5.6 million pounds in 1983. 

During the early years of the offshore 

lobster fishery, most vessels used 

otter trawls to capture lobsters, but 

since the late 1960's most vessels use 

large lobster pots set in long strings 

YEARS 

Figure 2. Estimated increase in catch 

of offshore lobsters, 1940-70 (Cobb 

1976). 

(Cobb 1976), something on the order of 

a longline. 

Lobsters are caught throughout 

the year in New England except for a 

restricted area near Monhegan Island, 

Maine, which is closed to lobstering 

from January 1 to June 25. The catch 

in New England is highest from August 

to November. 

Maine 

Mai ne produces the greatest 

number of lobsters. Landings in 1982 

were 22.5 million pounds with a 

dockside value of about $50 million 

(Table 2). 

Lobsters may only be caught with 

traps that are vented to a1 low 

individuals smaller than legal size to 

escape. Neither the number of traps 

per fisherman nor the number of 

1 icenses is restricted. Minimum size 

is 3 3/16 inches (81 mm) CLM (carapace 

length measured from the back @f the 

eye socket to the back of the 

carapace). Maine is the only state 

with a maximum size limit; all 

lobsters larger than 5 inches (127 mm 

CLM) must be released. 

Female lobsters carrying eggs 

attached to their pl eopods (berried) 

have been protected in a1 1 lobster 

producing states since the late 19th 

century (Dow 1980). Lobsters that 

extrude eggs while being held in 

holding pens in Maine are purchased by 

the State, marked with a "V"-notch in 

the telson, and released in the sea. 

"V"-notched lobsters are protected in 

Maine and must be released whether or 

not they are berried at the time of 

recapture. 

New Hampshire 

Lobsters in New Hampshire are 

taken by traps or trawl. The trawl 

fishery is not directed at lobsters 

but an incidental catch of lobsters is 

a1 lowed. The 1982 commercial catch 

was 807,000 Ib, valued at $1.8 million 
Table 2. Landings (thousands of pounds) and dockside values (thousands 

of do1 lars) of American lobsters in Maine, New Hampshire, and Massachusetts fra 1963-1982. (Fishery Statistics of the United States, 

1963-64, 1969-70; New England Fisheries, 1971-76; N.M. F.S. unpublished 

data, 1977-82). 

Mai ne New Hampshire Massachusetts 

Years Landings Val ue Landings Val ue Landings Val ue 

Massachusetts 

(Table 2). The minimum size limit in 

New Hampshire is 3 3/16 inches (81 mm) The State has a limited entry 

CLM. There is no limit to the number inshore commercial fishery. In 1983, 

of traps that can be set by commercial the number of coastal lobster permits 

lobster fishermen. New Hampshire issued was limited to 1,608. Vented 

sells a recreational lobster 1 icense traps are used in the coastal fishery; 

that allows the holder to set 5 traps. there is no 1 imit on the number of 
traps that can be set by each fisherman. An incidental catch of 100 

lobsters per day is allowed for 

inshore trawlers. The number of 

permits for the offshore fishery is 

unlimited and both traps and trawls 

are legal gear. The minimum length 

in Massachusetts is 3 3/16 inches 

(81 mm) CLM. 

Landings in 1982 had a dockside 

value of $25,596,000 (Table 2). 

Massachusetts has a 1 arge recreational 

fishery . About 11,000 non-commercial 

licenses were issued in 1983. Permit 

holders are allowed to set 10 lobster 

traps. Lobsters can be taken 1 egal ly 

by skin or SCIIBA-divers in Massachusetts but not in the other New 

England States. 

The New England Regional Fisheries Management Council has developed 

a management plan for the offshore 

(3-200 mi les) 1 obster fishery that 

will take effect on January 1, 1985. 

For example, the minimum length limit 

for offshore lobsters will be 3 3/16 

inches (81 mm) CLM. 

POPULATION DYNAMICS 

Natural mortal ity is extremely 

high during the free-swimming planktonic larval stages of the American 

lobster. Scarratt (1964, 1973) used 

larval stage abundance to estimate the 

survival from stage I to stage IV of 

larvae in the southern Gulf of St. 

Lawrence, New Brunswick. Average 

annual survival was about 0.9% (range 

0.1 to 2.5). The percentage survival 

may have been underestimated because 

of the difficulty in estimating the 

abundance of stage IV larvae. Larvae 

become negatively phototactic midway 

through stage IV and may not have been 

collected in surface tows that were 

used to estimate abundance (Scarratt 

1973). 

Estimates of mortal i ty of 

juvenile and adult lobsters in United 

States waters were reviewed by Anthony 

(1980). Estimates of instantaneous 

total mortality (Z) . from Maine, New 

Hampshire, Massachusetts, Rhode 

Island, New York, New Jersey, and 

Virginia averaged 1.84 (range 0.91 to 

2.80). Estimates of instantaneous 

natural mortal ity (M) ranged from 0.02 

to 0.35 with an average of 0.15. 

Mortal i ty estimates of lobster 

populations in the Canadian Maritimes 

were reviewed by Campbell (1980). 

Several methods were used to 

estimate the mortality of juvenile and 

adult lobsters along the coast of 

Maine (Thomas 1973). Instantaneous 

total mortality (Z) of commercial-size 

lobsters (> 81 mn) ranged from 1 .I363 

to 2.9188. Instantaneous natural 

mortal ity (M) for pre-recrui t (less 

than commerci a1 size) lobsters ranged 

from 0.0202 to 0.3467. Estimates of 

instantaneous fishing mortality (F) 

ranged from 0.7896 to 2.8986. These F 

values represent an annual expl oitation rate of 54.6% to 84.5% of the 

1 obsters vulnerable to the commerci a1 

fishery . 

Annual exploitation rates of 

lobsters near Comfort Cove, Newfoundland, were as high as 95% (Ennis 

et al. 1982). For 1977-81, annual 

exploitation rates of lobsters near 

Notre Dame Bay, Newfound1 and, varied 

from 80% to 95% (Ennis 1983). 

Lobster movements usually are 

triggered by changes in water 

temperature (McLeese and Wilder 1958; 

Paloheimo 1963; Cooper and Uzmann 

1971 ) . A strong correl a t i o n between 

catch, fishing effort, and sea surface 

temperature was reported by Dow et al. 

(1975). Lobster yield predictions for 

Maine, based on sea surface temperatures, were calculated by Flowers and 

Saila (1972). Saila and Marchessault 

(1980) discuss other models that have 

been developed to predict the yield of 

lobsters and summarize the surplusyield models that have been used. 
ECOLOGICAL ROLE 

Feeding Habits 

American lobster larvae have been 

cultured on copepods and small lobster 

larvae but little is known about their 

feeding habits in nature. Larvae were 

raised on a diet of the copepods, - Acartia , Tortanus, Eurytemora, and 

Pseudocalanus, and grew we1 1 on a diet 

of smal ler lobster larvae (Templeman 

1936~). Two larvae collected in Vineyard Sound, Massachusetts, contained 

parts of crustacea, diatoms, and algae 

(Herrick 1895). 

Juveni 1 e and adult 1 obsters are 

omnivorous. They are primarily predators, catching live prey, but they 

also scavenge for food (Ennis 1973). 

The bulk of their diet consists of 

bottom invertebrates, crabs, sea 

urchins, mussels, polychaetes, periwinkles, and sea stars (Herrick 1895, 

1909; Miller et al. 1971; Ennis 1973). 

Fish and plants also contribute to the 

diet (Herrick 1895; Ennis 1973). In a 

report by Ennis (1973) crabs, Cancer 

irroratus and Hyas araneus, made up 

0% of the volume of food in the 

stomachs of lobsters collected in 

Bonavi sta Bay, Newfound1 and. Sea urchins, ~tr6n~~locentrotus droebachiensis, were the next most important 

food7%). 

American lobsters apparently 

prefer to eat crabs. The responses of 

lobsters to the waterborne odors of 

crabs (Carcinus maenas), sea urchins, 

and mussels (Mytilus edulis) 

demonstrate that lobsters are 

attracted by crab odor more than the 

other two (Hirtle and Mann 1978). 

Lobsters prefer rock crabs (Cancer 

irroratus) over sea urchins whenboth 

are present in aquaria (Evans and Mann 

1977). 

Sea urchins and sea stars 

contribute a much larger proportion of 

the diet during the molting season 

than at other times of the year (Ennis 

1973). This change in diet during 

molting may be one of selectivity for 

prey high in calcium, an important 

el ement in hardening the exoskeleton. 

The diets of female and male 

lobsters (47-113 mm CL) are similar 

(Ennis 1973). Feeding activity 

declines in the fall as water 

temperatures decrease, and remai ns low 

in winter. 

Predation 

Juveni 1 e and adult American 

lobsters are consumed by many bottom 

feeding fishes. Atlantic cod stomachs 

often are filled with juvenile 

1 obsters (Herri ck 1895). Most 

lobsters eaten by fish are less than 

50 mm CL, but larger lobsters are 

eaten by Atlantic cod, sharks, 

wolffish, pollock, and goosefish 

(Herrick 1895; Cooper and Uzmann 

1980). Skates, rays, cunner, tautog, 

striped bass, black sea bass, sea 

ravens, haddock, ti 1 efi shy conger 

eels, and weakfish sometimes prey upon 

juveni le lobsters (Herrick 1895; 

Cooper and Uzmann 1977). Predators 05 

lobster larvae have not been 

identified but the planktonic larvae 

probably a re consumed by 

surface-feeding pl ankt ivorous fishes. 

Diseases and Parasites 

Few diseases are known at the 

present time which affect the American 

lobster. Gaffkemi a (Aerococcus 

vi ridans var. homari ) and "she1 1 " 

disease are two bacteri a1 diseases 

that cause high mortality in holding 

pens (Stewart 1980). Incidence of 

gaffkemia in lobsters from natural 

populations along the Maine coast 

averaged 7% (Vachon et al. 1981). 

Lobsters also are infected with fungal 

diseases and epibiotic growths. 

Mussels, barnacl es, marine a1 gae, 

fi 1 amentous bacteria, stalked 

protozoans, and di atoms sometimes may 

compl etely cover the exoskel eton 

(Herrick 1909: McLeese and Wilder 

1964). A trematode (Stichocot le 

nephropsi s), copepod (Und 
Acanthocephel a, and protozoa (Porospora igantea, Anophys sp.) are 

oarasite: of the lobster (Stewart 

ENVIRONMENTAL REQUIREMENTS 

Temperature, salinity, and 

substrate are the most critical 

factors influencing 1 obster 

distribution and abundance. Also 

there is some evidence that lobster 

activity and feeding may be light 

dependent. Critical environmental 

factors are discussed below. 

Temperature 

Eggs of American lobsters hatch 

at water temperatures as low as 8°C 

in northern New England (Fogarty and 

Lawton 1983). At the Massachusetts 

State Lobster Hatchery the lowest 

temperature at which hatching was 

observed was 9.4"C (Hughes and 

Matthiessen 1962). Hatching usually 

begins when water temperatures are 

about 15°C and peaks near 20°C. 

The average surface water 

temperatures during peak larval 

densities in Boothbay Harbor, Maine, 

range from 13.7" to 15.0°C (Sherman 

and Lewis 1967). These water 

temperatures are the maximum for the 

region. Larval densities in Buzzards 

Bay, Massachusetts, peaked when the 

surface water temperature was about 

19°C and the bottom water temperature 

was about 17°C (Lux et al. 1983). 

Surface water temperatures ranged from 

10.3 to 25.5"C when larvae were 

collected in Cape Cod Canal, Buzzards 

Bay, and Cape Cod Bay, Massachusetts 

(Collings et al. 1983). 

The development of larvae is 

temperature dependent. Larvae 

attained stage V (which marks the end 

of the pelagic larval period) within 

28 days after hatching at a water 

temperature of 19°C. Stage V was 

achieved in 50 days at 14"C, and 100 

days at 10°C (Templeman i936c). 

Lobster larvae are less tolerant to 

low temperatures than juveniles or 

adults. In one experiment all larvae 

died prior to molting at 5°C (Huntsman 

1924). 

Juveni 1 e and adult American 

lobsters tolerate sea water temperatures ranging from -1 to 30.5OC 

(Huntsman 1924, McLeese 1956). 

Molting and growth cease when water 

temperatures drop below 5°C (Aiken 

1980). The upper 1 ethal temperatures 

(LD in 48 h). of lobsters (16 to 34. 

cm '?otal length measured from tip ,of 

rostrum to tip of telson) acclimated 

to 27 combinations of temperature (5", lo0, lS°C), salinity (20, 25, 30 ppt), 

and dissolved oxygen (2.9, 4.3, 6.9 

mgll) were reported by McLeese (1956). 

Accl imation conditions si.gni ficantly 

affected the upper lethal temperature. 

Upper 1 ethal temperatures ranged from 

20.6"C for lobsters acclimated at 5"C, 

20 ppt salinity, and 2.9 mgll O2 to 

30.5"C for lobsters acclimated at 

2S°C, 30 ppt salinity, and 6.4 mg/l 

O2 (Table 3). 

Changes in water temperature 

stimulate migrations of offshore 

lobsters which tend to seek bottom 

water temperatures from 8 to 14°C 

(Uzmann et al. 1977). During the 

spring, lobsters offshore move from 

the outer Continental Shelf and upper 

slope to shallower water along the 

southern New England Continental 

Shelf, including Georges Bank and the 

coastal waters of New York, Rhode 

Is1 and, and southern Massachusetts. 

It is possible that bottom water 

temperatures (8 to 14°C) in the 

shallower waters are more suitable for 

the extrusion of eggs, molting, and 

mating than are the summer bottom 

temperatures over the outer Conti nental Shelf and upper slope (Cooper and 

Uzmann 1971). Return lobster 

migrations to the outer shelf and 

upper slope waters begin in late 

summer and continue through November 

as inshore bottom water temperatures 

drop. By December the lobsters 

offshore have returned to the outer 
Table 3. Upper lethal temperatures and lower lethal salinity and oxygen 

concentrations for American lobsters acclimated to 27 combinations of temperatu re, sal i ni ty , and oxygen (McLeese 1956). 

Lower Lower 

Acclimation conditions Upper lethal lethal 

Temperature Sal i ni ty Oxygen lethal salinity oxygen 

("C) (PP~) (mg/l) temp. (PP~) (mg/l) 
shelf and upper slope waters where 

bottom temperatures are 8 to 12OC 

(Uzmann et al. 1977). 

Salinity 

Studies of American lobster 

larvae exposed to various sal ini ties 

in water temperatures of 15.0 to 

17.5OC, reveal ed that survival was 

highest at a salinity of 30 ppt and 

salinities as low as 21 ppt were only 

slightly less suitable (Templeman 

1936). Survival of larvae to stage 

IV decreased as sal ini ties dropped 

below 21 ppt, and no larvae survived 

less than 17.0 ppt. Larvae attempted 

to avoid salinities as low as 21.4 ppt 

at water temperatures near 22OC 

(Scarratt and Raine 1967). There is 

no information on survival rates of 

lobsters at unusually high sal inities. 

The lower lethal salinity levels 

(LD+O in 48 hours) of juvenile and 

adu t lobsters acclimated to 27 

. combinations of salinity, dissolved 

oxygen, and water temperature were 

reported by McLeese (1956). Lower 

lethal salinities ranged from 6 ppt 

for lobsters acclimated at 5OC, 6.4 

mgll 02, and 30 ppt salinity to 16.4 

ppt for lobsters acclimated at 25OC, 

6.4 mg/l 02, and 30 ppt salinity 

(Table 3). Due to osmoregulatory 

stress, molting lobsters are less 

resistant to low salinities than 

hard-shelled lobsters. 

Dissolved Oxygen 

American lobsters can survive 

re1 atively low dissolved oxygen 

concent rations. McLeese (1956) 

reported that the lower lethal oxygen 

concentration was 0.2 mgll for 

lobsters acclimated at 5OC and 30 ppt 

salinity and rose to 1.7 mgll at 

acclimation conditions of 25OC and 20 

ppt salinity (Table 3). Acclimation 

1 eve1 s of temperature and sal i ni ty 

significantly affected the lower 

lethal oxygen concentration whereas 

acclimation level of oxygen did not 

have a si gni fi cant effhct (McLeese 

1956). 

Substrate 

Juvenile and adult American lobsters occupy substrates characterized 

by sand-rock, bedrock-rock, mud-rock, 

mud-silt, and clay-silt (Thomas 1968; 

Cobb 1971; Cooper et al. 1975; Cooper 

and Uzmann 1980). The most common 

substrate occupied by inshore 1 obsters 

is sand with overlying boulders. This 

substrate is uncommon in offshore 

areas where it is usually restricted 

to the heads of submarine canyons 

(Cooper and Uzmann 1980). The most 

common substrates in offshore areas 

are mud or clay with overlying silt. 

Lobsters burrow or excavate bowlshaped 

depressions into these soft substrates 

for cover and protection (Cooper and 

Uzmann 1980). 

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Pages 91-163 in J.S. Cobb and 

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215-276 in -J.S. Cobb and B.F. 

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Board Can. 30: 1819-1824. 

Scarratt, D.J., and G.E. Raine. 1967. 

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1406. 

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50272 -101 

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

I REPORT DOCUMENTATION i 'LRE~~~ 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 iterature summaries of the taxonomy, morphology, distribution, 1 ife 

hi story, and environmental requirements of coastal aquatic species. They are designed to 

assist in environmental impact assessment. The American 1 obster (Homarus americanus) is 

a valuable commercial shellfish. After spawning, lobsters undergo a series of molts; as 

adults they live 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. 

Lobsters 

Growth 

Document Analysis a. Descriptors I 

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 

C 20. Security Class (This Page) 

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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