QL

155

.S63

no.82-

11.76

Biological Report 82 (11.78)

August 1987

Species Profiles: Life Histories and

Environmental Requirements of Coastal Fishes

and Invertebrates (North Atlantic)

ATLANTIC TOMCOD

Fish and Wildlife Service

Coastal Ecology Group

Waterways Experiment Station

U.S. Department of the Interior U.S. Army Corps of Engineers

Biological Report 82(11.76)

TR EL-82-4

August 1987

Species Profiles: Life Histories and Environmental Requirements

of Coastal Fishes and Invertebrates (North Atlantic)

ATLANTIC TOMCOD

Lance L. Stewart and Peter J. Auster

NOAA's National Undersea Research Program

The University of Connecticut at Avery Point

Groton, CT 06340

Project Manager

Carroll Cordes

Project Officer

David Moran

U.S. Fish and Wildlife Service

National Wetlands Research Center

1010 Gause Boulevard

Slidell, LA 70458

Performed for

Coastal Ecology Group

U.S. Army Corps of Engineers

Waterways Experiment Station

Vicksburg, MS 39180

and

U.S. Department of the Interior

Fish and Wildlife Service

Research and Development

National Wetlands Research Center

Washington, DC 20240

W
c

This series may be referenced as follows:

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

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

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

This profile may be cited as follows:

Stewart, L.L., and P.J. Auster. 1987. Species profiles: life histories and

environmental requirements of coastal fishes and invertebrates (North

Atlantic)--Atlantic tomcod. U.S. Fish Wildl. Serv. Biol. Rep. 82(11.76). U.S.

Army Corps of Engineers, TR EL-82-4. 8 PP.
PREFACE

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

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

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

comprehensive sketch of the biological characteristics and environmental

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

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

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

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

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

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

and the U.S. Fish and Wildlife Service.

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

the following addresses.

Information Transfer Specialist

National Coastal Ecosystems Team

U.S. Fish and Wildlife Service

NASA-Slide11 Computer Complex

1010 Gause Boulevard

Slidell, LA 70458

or

U.S. Army Engineer Waterways Experiment Station

Attention: WESER-C

Post Office Box 631

Vicksburg, MS 39180

iii
CONVERSION TABLE

Multiply .Q To Obtain

millimeters (mm) 0.03937 inches

centimeters (cm) 0.3937 inches

meters (m) 3.281 feet

meters (m) 0.5468 fathoms

kilometers (km) 0.6214 statute miles

kilometers (km) 0.5396 nautical miles

square meters (me) 10.76 square feet

square kilometers (km*) 0.3861 square miles

hectares (ha) 2.471 acres

liters (1) 0.2642 gallons

cubic meters (m3) 35.31 cubic feet

cubic meters (m3) 0.0008110 acre-feet

milligrams (mg) 0.00003527 ounces

grams (9) 0.03527 ounces

kilograms (kg) 2.205 pounds

metric tons (t) 2205.0 pounds

metric tons (t) 1.102 short tons

kilocalories (kcal) 3.968 British thermal units

Celsius degrees ("C) 1.8("C) + 32 Fahrenheit degrees

inches

inches

feet (ft)

fathoms

statute miles (mi)

nautical miles (nmi)

U.S. Customary to Metric

25.40

2.54

0.3048

1.829

1.609

1.852

millimeters

centimeters

meters

meters

kilometers

kilometers

square feet (ft2) 0.0929 square meters

square miles (mi*) 2.590 square kilometers

acres 0.4047 hectares

gallons (gal) 3.785 liters

cubic feet (ft") 0.02831 cubic meters

acre-feet 1233.0 cubic meters

ounces (oz) 28350.0 milligrams

ounces (oz) 28.35 grams

pounds (lb) 0.4536 kilograms

pounds (lb) 0.00045 metric tons

short tons (ton) 0.9072 metric tons

Metric to U.S. Customary

British thermal units (Btu)

Fahrenheit degrees (OF)

0.2520

0.5556 (OF

iv

kilocalories

32) Celsius degrees
l

CONTENTS

PREFACE ...................................

CONVERSION TABLE ..........................

ACKNOWLEDGMENTS ...........................

NOMENCLATURE/TAXONOMY/RANGE ....

MORPHOLOGY/IDENTIFICATION AIDS .

REASON FOR INCLUSION IN SERIES

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

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

Fecundity and Eggs ...........

Larvae .......................

Juvenile and Adults ..........

GROWTH CHARACTERISTICS .........

FISHERY ........................

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

ENVIRONMENTAL REQUIREMENTS .....

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

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

Habitat ......................

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LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . .

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Page

iii

iv

vi

V
ACKNOWLEDGMENTS

We are grateful for the review by W. Smith and T. Pacheco of the National

Marine Fisheries Service, Sandy Hook, New Jersey. We also thank Constance

Fontaine and Andrew Shepard for patiently dealing with drafts and the computer.

Mary Jane Spring expertly prepared figure 1.

vi
Figure 1. Atlantic tomcod (Microgadus tomcod).

NOMENCLATURE/TAXONOMY/RANGE

Scientific name ._.._.

tomcod (Walbaum)

Preferred common name

tomcod (Figure 1)

Other common name . . . .

Class . . . . . . . . . . . . . . . .

Order . . . . . . . . . . . . . . . .

Family . . . . . . . . . . . . . . .

. . . . Microgadus

. . . . . . Atlantic

. . . . . Frostfish

. . Osteichthyes

. . . . Gadiformes

. . . . . . . Gadidae

Geographic range: Coastal waters of

the northwest Atlantic from southern

Labrador and northern Newfoundland

to Virginia (Figure 2). Generally

occurring in brackish water but

occasionally in freshwater (Bigelow

and Schroeder 1953; Leim and Scott

1966).

MORPHOLOGY/IDENTIFICATION AIDS

Bigelow and Schroeder (1953) and

Leim and Scott (1966) provided

complete descriptions of the Atlantic

tomcod and guides for its differentiation from other species. Atlantic

tomcod generally have the same body

plan as the much larger Atlantic

cod (Gadus morhua). - - The body is

elongated, and the upper jaw projects

past the lower jaw. There is a

barbel on the chin. Differences in

several key external characters

allow easy differentiation: The

second rays of the ventral fins of

the tomcod are long, narrow, and

tapering (the tapered portion is

as long as the rest of the fin),

whereas those of the cod are shorter,

broad, and rounded (the filament is

one-quarter the length of the fin).

The caudal fin of the tomcod is

rounded, in contrast to the squarish

fin of the cod. Coloration of the

tomcod is olive, olive-brown, or

muddy green, with some yellow on

the dorsal surface; lower lateral

surfaces have a more yellowish cast,

especially in larger fish; dorsal

fins are mottled with dark spots

or blotches; and the belly is gray

or yellow-white and the margin of

the anal fin is olive.

Booth (1967) and Hardy (1978)

provided descriptions of the

development of eggs and larvae,

which can be distinguished from

other species on the basis of

morphology.

1
MAINE

1 CANADA \

\

ATLANTIC OCEAN

Coastal distribution

0 5 0

-

, 100 ,I

0 5 0 100

KILOMETERS

MILES

Figure 2. Coastal distribution of the Atlantic tomcod (Microgadus tomcod) in the

North Atlantic region.

2
REASON FOR INCLUSION IN SERIES

Altantic tomcod are widespread

along coastal regions of the northeastern coast of the U.S. They are

abundant in estuarine habitats such as

river mouths and salt marshes. These

same habitats are subject to a wide

variety of human sources of disturbance.

LIFE HISTORY

Spawning

Although the range of the tomcod

extends south to Virginia, no spawning

has been reported in estuaries south

of the Hudson River (DeSylva et al.

1962; Schwartz 1964; Massmann 1975);

however, spawning occurs in many

estuaries in the northern part of the

range. North of the Hudson River,

tomcod spawn from November to February

with a peak in January (Vladykov 1955;

Pearcy and Richards 1962; Howe 1971;

Dew and Hecht 1976; Able 1978).

Spawning occurs in shallow waters of

estuaries or stream mouths, in salt,

brackish, or freshwater (Nichols and

Breder 1926; Bigelow and Schroeder

1953).

Fecundity and Eggs

Females 170 to 340 mm long

produce an average of 20,000 eggs

within a range of 6,000 to 30,000

(Schaner and Sherman 1960). Nichols

and Breder (1926) reported that

average fecundity was 25,000 eggs

(maximum 44,000).

The eggs of Atlantic tomcod are

large, approximately 1.5 mm in diameter, and have a large oil globule.

They sink to the bottom after spawning

and adhere in masses to available

substrate (Bigelow and Shroeder 1953;

Dew and Hecht 1976).

Salinity affects fertilization,

development, and subsequent hatching

success. Sperm motility is greatest

at low salinities (Booth 1967); hence

fertilization success is also highest

at low salinity. Eggs generally occur

and develop mostly in freshwater, due

to stream flow characteristics at the

heads of estuaries; seawater intrusion

occurs only at extreme high tides.

Normal development does not occur

when eggs are continuously exposed to

salinities of 30 ppt or higher

(Peterson et al. 1980). Booth (1967)

found that the percentage of eggs that

developed to the blastula stage was

highest when salinities ranged from

0 to 15 ppt.

Incubation time is approximately

30 days at 6.1 OC and 24 days at

4.4 “C (Bigelow and Schroeder 1953).

Peterson et al. (1980) demonstrated

that time to hatching decreases as

salinity increases (up to 30 ppt).

For example, at temperatures between

approximately 4 and 9 “C, median times

of hatching were reduced from 53 days

at 0 ppt to 38 days at 30 ppt (at 30

ppt development was abnormal).

Larvae

Atlantic tomcod larvae became

photopositive within 24 h after

hatching, and swim to the surface

to inflate the swim bladder by

gulping air. Larvae are transported

seaward as water temperatures

begin to increase (Peterson et al.

1980).

Larvae are most abundant in the

water column in early March in

southern New England (Booth 1967;

Howe 1971). They are generally found

near bottom in the (low salinity)

upper reaches of estuaries (Pearcy

and Richards 1962; Howe 1971).

This distribution pattern would

3

Table 2. Age composition by total

lengths of Atlantic tomcod collected

from Weweantic River, 1966-67 (from

Howe 1971).

Age group

Total Total (entire sample

length no. of included)

(mm) fish 0 I II III

45-99 347 347

100-119 36 31 5

120-204 117 117

205-244 36 10 26

245-279 20 20

280-319 7 3 4

Total 563 378 132 49

(67%) (23%) (9%) (I&

southern New England were 63-77 mm

long in fall. These values agree

with the growth found in the more

northern populations in Massachusetts

by Howe (1971).

Tomcod may grow larger during

their first year in southern New

England than those in the Canadian

Maritimes. Leim and Scott (1966)

reported that young-of-the-year fish

reached only 57 mm by August, although

they also reported the longest tomcod

at 330 mm.

The model describing the relation

between length and weight follows:

log W(g) = 5.1087 + 3.032 log L(mm)

where r = 0.995 for both sexes (Howe

1971). No statistically significant

differences between sexes were found.

Growth rates of tomcod are

highest from January, February, or

March (according to region) through

July. Feeding is heaviest after the

fish spawn, as water temperatures

increase (Howe 1971).

FISHERY

Tomcod were a locally important

commercial target species in northern

estuaries during the 1800's. Storer

(1839) reported that they were locally

abundant near Boston, where 2,000 bu

were landed annually at Watertown.

Goode (1888) reported that 10,000 lb

were landed annually from the Charles

River, where they were marketed as

"London trout" and considered a

delicacy. The importance of the

commercial tomcod fishery declined

along the New England coast during the

past century. There have been no

catch statistics for this species in

New England since small amounts were

landed at Point Judith in 1957 and

reported by Edwards (1958). Leim and

Scott (1966) reported that tomcod are

taken incidentally in the smelt trap

fishery in Canada, and are sometimes

caught by hand line and hoop net.

They are also taken in a winter ice

fishery in the St. Lawrence River.

One million pounds, worth $26,000,

were landed in the Canadian Atlantic

area in 1962. Tomcod are now the

target of a winter sport fishery along

the New England coast.

ECOLOGICAL ROLE

Atlantic tomcod feed principally

on small crustaceans and to a lesser

extent on polychaete worms, mollusks,

and fish (Bigelow and Schroeder 1953;

Howe 1971; Grabe 1978, 1980).

Little is known about predation

on tomcod by piscivorous fishes. A

study by Dew and Hecht (1976) in the

Hudson River, New York, suggested that

yearling striped bass, Morone

saxatilis, selectively prey on tomcod

during summer, when other prey species

of suitable size (i.e., juvenile

herrings) are not available. Tomcod

may serve as an alternate prey species

for striped bass during years when

their primary prey, the bay anchovy

(Anchoa mitchilli), is scarce. In

some river-estuarine systems, the

5
tomcod may be an alternate prey

resource critical to the continuous

production of striped bass.

ENVIRONMENTAL REQUIREMENTS

Temperature

Coastal, estuarine, and riverine

water temperatures along the northeast

coast vary over a wide range. Howe

(1971) found no fish at water

temperatures higher than 26 OC.

Kellogg et al. (1978) determined that

the upper lethal temperature of tomcod

eggs was 6.6 OC. Tomcod have been

found at temp,eratures as low as

-1.2 OC (Gordon et al. 1962);

glycoproteins that depress the

freezing point enable the fish to

avoid freezing (Fletcher et al. 1982).

Salinity

In the Hudson River, Dew and

Hecht (1976) found the densities of

larvae and juveniles to be highest

within a salinity range of 4.5 to

8.7 ppt; the total range was 1.5 to

10.0 PPt. Howe (1971) found

young-of-the-year in areas with

salinity higher than 10.0 PPt.

Juveniles and adults have been found

at all salinities from full-strength

seawater to freshwater, in bays and

estuaries (Bigelow and Schroeder 1953;

Leim and Scott 1966).

Habitat

Tomcod are found at the high tide

mark of saltmarshes and mudflats

(Dutil et al. 1982), in eelgrass beds

(Howe 1971), and to an approximate

maximum depth of 6 m in bays,

estuaries, and coastal waters within

about 1.6 km of shore (Bigelow and

Schroeder 1953). Tomcod are also

reported to ascend rivers well beyond

the furthest point of seawater

intrusion (Bigelow and Schroeder 1953;

Leim and Scott 1966).
LITERATURE CITED

Able, K.W. 1978. Ichthyoplankton of

the St. Lawrence Estuary:

composition, distribution, and

abundance. J. Fish. Res. Board Can.

35:1518-1531.

Bigelow, H.B., and W.C. Schroeder.

1953. Fishes of the Gulf of Maine.

U.S. Fish Wildl. Serv. Fish. Bull.

53:1-577.

Booth, R.A. 1967. A description of

the larval stages of the tomcod,

Microgadus tomcod, with comments on

its spawning ecology. Ph.D. Thesis.

University of Connecticut, Storrs.

53 PP.

DeSylva, D.P., F.A. Kalber, and C.N.

Shuster, Jr. 1962. Fishes in the

shore zone and other areas of the

Delaware Estuary. Univ. Del. Mar.

Lab. Inf. Ser. No. 5:1-164.

Dew, C.B, and J.H. Hecht. 1976.

Observations on the population

dynamics of Atlantic tomcod

(Microgadus tomcod) in the Hudson

River Estuary. Proc. 4th Symp. on

Hudson River Ecology. Paper 25.

Hudson River Environmental Society,

Bronx, N.Y.

Dutil, J.D., M. Fortin, and Y.

Vigneault. 1982. L'importance des

zones littorales pour les resources

halieutiques. Can. MS. Rep. Fish.

Aquat. Sci. No. 1653F. 32 PP .

Edwards, R.I. 1958. Species

composition of industrial trawl

landings in New England, 1957. U.S.

Fish Wildl. Serv. Spec. Sci. Rep.

Fish. No. 266. 23 PP.

Fletcher, G.L., C.L. Hew, and S.B.

Joshi. 1982. Isolation and

characterization of antifreeze

qlvcoproteins from the frostfish.

Microgadus tomcod. Can. J. Zool:

60:348-355.

Goode, G.B. 1888. American fishes.

W.A. Houghton, N.Y. 496 pp.

Gordon, M.S., B.H. Amdur, and P.F.

Scholander. 1962. Freezing

resistance in some northern fishes.

Biol. Bull. (Woods Hole) 122:52-56.

Grabe, S.A. 1978. Food and feeding

habits of juvenile Atlantic tomcod,

Microgadus tomcod, from Haverstraw

Bay, Hudson River, New York. U.S.

Natl. Mar. Fish. Serv. Fish. Bull.

76:89-94.

Grabe, S.A. 1980. Food of age 1 and

2 Atlantic tomcod, Microgadus

tomcod, from Haverstraw Bay, Hudson

River, New York. U.S. Natl. Mar.

Fish. Serv. Fish. Bull.

77:1003-1006.

Hardy, J.D. , Jr. 1978. Development

of fishes of the mid-Atlantic Bight,

an atlas of egg, larval, and

juvenile stages. Vol. 2:Anguillidae

through Syngnathidae. U.S. Fish.

Wildl. Serv. Biol. Serv. Program

FWS/OBS-78/12. 458 pp.

Howe, A.B. 1971. Biological

investigations of Atlantic tomcod,

Microgadus tomcod (Walbaum), in the

Weweantic River Estuary,

Massachusetts, 1967. M.S. Thesis:

University of Massachusetts,

Amherst. 82 PP.
Kellogg, R.L., J.J. Salerno, and D.L.

Latimer. 1978. Effects of acute

and chronic thermal exposure on the

eggs of three Hudson River

anadromous fishes. Tech. Info.

Center, U.S. Dep. Energy, Oak Ridge,

Tenn. DOE Symp. Ser. No. 48:714-725.

Leim, A.H., and W.B. Scott. 1966.

Fishes of the Atlantic Coast of

Canada. Fish. Res. Board Can. Bull.

No. 155. 485 pp.

Massman, W.H. 1957. New and recent

records for fish in Chesapeake Bay.

Copeia 1957:156-167.

Nichols, J.T., and C.M. Breder. 1926.

The marine fishes of New York and

southern New England. Zoologica

9:1-192.

Pearcy, W.G., and S.W. Richards.

1962. Distribution and ecology of

fishes of the Mystic River Estuary,

Connecticut. Ecology 43:248-259.

Peterson, R.H., P.H. Johansen, and

J.L. Metcalfe. 1980. Observations

on early life stages of Atlantic

tomcod, Microgadus tomcod. Natl.

Mar. Fish. Serv. Fish. Bull.

78:147-158.

Schaner, E., and K. Sherman. 1960.

Observations on the fecundity of the

tomcod, Microgadus tomcod (Walbaum).

Copeia 1960:347-348.

Schwartz, F.J. 1964. Fishes of Isle

of Wight and Assawoman Bays near

Ocean City, Maryland. Chesapeake

Sci. 5:172-193.

Storer, D.H. 1839. Fishes of

Massachusetts. Dutton and

Wentworth, Boston. 426 pp.

Vladykov, V.D. 1955. Fishes of

Quebec-Cods. Quebec Dep. Fish.

Album No. 4:1-12.

Warfel, H.E., and D. Merriman. 1944.

Studies on the marine resources of

southern New England. Vol. 1: An

analysis of the fish population of

the shore zone. Bull. Bingham

Oceanogr. Coll. 9(2):1-91.
REFORT GOCUMENTATION 1. “Ema~ ~0. 2.

PAGE Biological Report 82(11.76)*

4. m*~ndsumnl~

Species Profiles: Life Histories and Environmental

Requirements of Coastal Fishes and Invertebrates

(North Atlantic)--Atlantic Tomcod

7. Autbww

Lance L. Stewart and Peter J. Auster

i. hr(ormh!g O~w~lzattoot N*me and Addns8

3. RadPhlt’m Acc*sslon NO.

% n*Poli Pa19

August 1987

&

a f+wfomlin# O~wliutlon R.pt. N

1Q Pmiact/l~sk/Work Unit No.

11. bntract(c) or Gnnt(G) No.

(0

12 Swn~ Oqanlzatlan N8ma and Addnas

(Cl

U.S. Department of the Interior U.S Army Corps of Engineers

Fish and Wildlife Service Waterways Experiment Station

National Wetlands Reserach Center P.O. Box 631

Washington, DC 20240 Vicksburg, MS 39180

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

1S. Abstract (Limit: 2M) words)

Species profiles are literature summaries on taxonomy, morphology, range, life

history, and environmental requirements of coastal finfishes and shellfishes. They

are designed to assist in environmental impact assessment. The Atlantic tomcod

(Microgadus tomcod) is of regional importance in a winter recreational sport fishery.

Tomcod are widespread along coastal regions of the northeast coast of the United

States. They are abundant in estuarine habitats such as river mouths and saltmarshes,

and thus are subject to a wide variety of anthropogenic sources of disturbance.

Tomcod spawn from November to March. Young-of-the-year remain in the estuary where

they were spawned during succeeding summer months. Adults live in full-strength

seawater to freshwater, but eggs and larvae have narrower salinity requirements.

17. Bacunm( hulyis a. O*sctipton

Estuaries Feeding habits

Fishes Life cycles

Fisheries Growth

Salinity Temperature

b. Idmtltten/Own-Endad Terms

Atlantic tomcod

Microgadus tomcod

c. COSATI FleldlGroup

1 la AvDll~bilitY Statement

Unlimited release

19. 9ecurity CIJSS (This Report) 21. No. of PaS*s

Unclassified 8 - -

20. Sacurity Class CThis Pace) a. price

Unclassified

(Jn ANSl-299.lSI OCTIONAL FORM 272 (4-7

(Fo,mwly NTlf35)

hpwtmwt ot Comm*rc9
As the Nation’s principal conservation agency, the Department of

the Interior has responsibility for most of our nationally owned

public lands and natural resources. This includes fostering the

wisest use of our land and water resources, protecting our fish

and wildlife, preserving the environmental and cultural values of our

national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses

our energy and mineral resources and works to assure that their

development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation

communities and for people who live in island territories under U.S.

administration.

U.S. DEPARTMENTOFTHEINTERIOR

FISH AND WILDLIFE SERVICE

w TAKE PRIDE

in America

UNITED STATES

DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

National Wetlands Research Center

NASA-Slide11 Computer Complex

1010 Gause Boulevard

Slidell. LA 70458