_

QL

155

.S63

L?brary

Nzanal Wetlands Research Center

Biological Report 82 (11.54)

July 1986

TR EL-82-4

Species Profiles: Life Histories and

Environmental Requirements of Coastal Fishes

and Invertebrates (South Florida)

SOUTHERN, GULF, AND SUMMER FLOUNDERS

no. 82 . _ . ____. ..“‘.,

11.54

Fish and Wildlife Service

U.S. Department of the Interior

Coastal Ecology Group

Waterways Experiment Station

U.S. Army Corps of Engineers

Biological Report 82(11.54)

TR EL-82-4

July 1986

Species Profiles: Life Histories and Environmental Requirements

of Coastal Fishes and Invertebrates (South Florida)

SOUTHERN, GULF, AND SUMMER FLOUNDERS .

Carter R. Gilbert

Florida State Museum

University of Florida

Gainesville, FL 32611

Project Manager

Larry Shanks

Project Officer

John Parsons

National Wetlands Research Center

U.S. Fish and Wildlife Service

1010 Gause Boulevard

Slidell, LA 70458

Performed for

Coastal Ecology Group

U.S. Army Corps of Engineers

Waterways Experiment Station

Vicksburg, MS 39180

and

National Wetlands Research Center

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 histo;i;s

and environmental requirements of coastal fishes and invertebrates. . .

Fish Wildl. Serv. 8iol. Rep. 82(11). U.S. Army Corps of Engineers, TR EL82-4.

This profile can be cited as follows:

Gilbert, C.R. 1986. Species profiles: life histories and environmental

requirements of coastal fikhes and invertebrates (South Florida)--southern,

gulf, and summer flounders. U.S. Fish Wildl. Serv. Biol. Rep. 82(11.54). U.S.

Army Corps of Engineers, TR EL-82-4. 27 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 Wetlands Research Center

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
Multiply !Y To Obtain

millimeters (nun)

centimeters (cm)

meters (m)

kilometers (km)

0.03937 inches

0.3937 inches

3.281 feet

0.6214 miles

square meters (m')

square kilometers (km')

hectares (ha)

10.76 square feet

0.3861 square miles

2.471 acres

liters (1)

cubic meters (m')

cubic meters

0.2642 gallons

35.31 cubic feet

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 1.102 short tons

kilocalories (kcal) 3.968 British thermal units

Celsius degrees l.S('C) + 32 Fahrenheit degrees

inches 25.40

inches 2.54

feet (ft) 0.3048

fathoms 1.829

miles (mi) 1.609

nautical miles (rmi) 1.852

square feet (ft2)

acres

square miles (mi2)

0.0929 square meters

0.4047 hectares

2.590 square kilometers

gallons (gal) 3.785

cubic feet (ft3) 0.02831

acre-feet 1233.0

ounces (oz)

pounds (lb)

short tons (ton) ,_ .

28.35 grams

0.4536 kilograms

0.9072 metric tons

British thermal units (Btu) 0.2520 kilocalories

Fahrenheit degrees 0.5556('F - 32) Celsius degrees

CONVERSION TABLE

Metric to U.S. Customary

U.S. Customary to Metric

millimeters

centimeters

meters

meters

kilometers

kilometers

liters

cubic meters

cubic meters

iv
CONTENTS

Page

iii

iv

vi

vii

:

2

2"

6

:

:

9

11

::

14

14

16

16

:87

:;

19

19

20

23

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

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

FIGURES. ...................................................................

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

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

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

Adults ...................................................................

Southern Flounder ......................................................

Gulf Flounder ..........................................................

Summer Flounder ........................................................

Postlarvae ...............................................................

REASON FOR INCLUSION IN SERIES .............................................

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

Reproduction .............................................................

Early Development Stages .................................................

Migration and Movement of Adults .........................................

Subpopulations ...........................................................

GROWTH CHARACTERISTICS .....................................................

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

Food and Feeding .........................................................

ENVIRONMENTAL REQUIREMENTS .................................................

Substrate ................................................................

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

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

Vegetation ...............................................................

Dissolved oxygen .........................................................

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

Quality and Value of Commercial Fishery ..................................

Sport Fishery ............................................................

LITERATURE CITED..................; ........................................

V
Number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

FIGURES

Southern flounder (Paralichthys lethostigma) . . . . . . . . . . . . . . . . . . .

Gulf flounder (Paralichthys albigutta) .........................

Summer flounder (Paralichthys dentatus) ........................

Areas of greatest abundance of southern flounder in

south Florida ..................................................

Areas of greatest abundance of gulf flounder in

south Florida ..................................................

Areas of greatest abundance of summer flounder

in south Florida ...............................................

Late postlarval pigmentation of summer flounder ................

Late postlarval pigmentation of southern flounder ..............

Egg development and yolk-sac larva of summer flounder ..........

Yolk-sac larva to larval stages of summer flounder .............

Larval stages of summer flounder ...............................

Length-weight relationship for summer flounder .................

Length-weight relationship for southern flounder ...............

Length-weight relationship for gulf flounder ...................

Percentage of volume and percentage of occurrence of

food items in seasonal diet of young summer flounder

and southern flounder from Pamlico Sound, North Carolina .......

Page

1

1

1

3

4

5

6

6

10

10

11

13

14

15

16

V i
ACKNOWLEDGMENTS

I wish to thank Ms. Rosemarie Mulholland, Florida Department of Natural

Resources, Clermont, Florida, for providing access to information she had compiled on the southern and gulf flounders while a graduate student at the University of Florida.

Museum,

I also wish to thank Mr. George H. Burgess, Florida State

University of Florida, Gainesville, for the loan of various reference

items used in preparation of this report. I wish to express my appreciation

to the journal CoPeia for permission to reproduce Figures 7 and 8, and to

Estuaries for permission to reprint Figure 15.

vii

Figure

(Paralichtiis

Southern flounder

lethostigma) (Powell

1974; redrawn from Ginsburg 1952).

Figure 2. Gulf flounder (Paralichthys

albigutta) (Powell 1974; redrawn from

Ginsburg 1952).

Figure flounder

(Paralichthi; denta%yer(Powell 1974;

redrawn from Ginsburg952).

SOUTHERN, GULF, AND SUMMER FLOUNDERS

NOMENCLATURE/TAXONOMY/RANGE

Scientific name Paralichthys

lethostigma Jordan'and Gilbert

Preferred common name . . . . . Southern

flounder (Figure 1)

Other common names . . . Mud flounder,

southern large flounder, doormat,

flounder, fluke, halibut

Scientific name . . . . . . . Paralichthys

albigutta Jordan and Gilbert

Preferred common name . . . . . . . . . Gulf

flounder (Figure 2)

Other common names . . Sand flounder,

flounder, fluke

Scientific name

dentatus (Linnaeusj"'

Paralichthys

Preferred- common name . . . . . . . Summer

flounder (Figure 3)

Other common names American

turbot, long-toothed"' flounder,

common flounder, flounder, fluke;

flounder of New York (New York);

plaice (New York, Massachusetts);

turbot (Massachusetts); flatfish

(Long Island, New York; Chesapeake

Bay!; chicken halibut, halibut,

brail, puckermouth (Rhode Island)

Class . . . . . . . . . . . . . . . . . Osteichthyes

Order . . . . . . . . . . . . Pleuronectiformes

Family . . . . . . . . . . . . . . . . . . . ..Bothidae
Geographic ranges:

Southern flounder: Occurs from

Albemarle Sound, North Carolina,

south to Loxahatchee River, on

lower east coast of Florida; it is

absent from there south and around

tip of peninsular Florida, but

occurs in Caloosahatchee River

Estuary, on southwest coast of

Florida, and from there around the

Gulf of Mexico to northern Mexico

(Hoese and Moore 1977; Manooch

1984) (Figure 4). Most common in

western half of the Gulf of Mexico. Generally occupies water of

lesser average depth than either

the gulf flounder or the summer

flounder. It is common to depths

of 47 m (Nail 1979); the greatest

confirmed depth is about 61 m

(Stokes 1977). Frequently occurs

in water of low salinity or even

freshwater (Ross 1980).

Gulf flounder: Ranges continuously

in coastal waters from Cape Lookout, North Carolina, to Corpus

Christi, Texas (Figure S), usually

in waters less than 92 m deep, but

occasionally as deep as 128 m

(Ginsburg 1952; Gutherz 1967). Has

occasionally been recorded from

extreme western Bahamas (Bohlke and

Chaplin 1968), and is most common

in eastern half of Gulf of Mexico

and along eastern coast of Florida.

Rarely enters waters of reduced

salinities, and never enters freshwater.

Summer flounder: Ranges from Gulf of

Maine (Bigelow and Schroeder 1953)

and occasionally Nova Scotia (Leim

and Scott 1966) south along Atlantic coast at least to Sebastian

Inlet, on southeast coast of Florida (Figure 6). Reports of occurrence in Gulf of Mexico (Poole

1962; Powell 1974; Rogers and Van

Den Avyle 1983) are in error (Ginsburg 1952; Gutherz 1967; Topp and

Hoff 1972; Hoese and Moore 1977;

Wilk et al. 1980; Manooch 1984).

Most common between Cape Cod and

Chesapeake Bay, usually in waters

less than 37 m deep, and occasionally down to 183 m; but occurs at

greater average depths to the

south. Rarely enters waters of

reduced salinities, and never

recorded from freshwater.

MORPHOLOGY/IDENTIFICATION AIDS

Adults

All species of Paralichthys are

relatively larae. robust. darkish,

lefteyed "flatfishes with jarge mouths

(upper jaw extending to or beyond

posterior margin of eye) and welldeveloped teeth. The bases of both

pelvic fins are short and neither

extends forward to the urohyal bone.

Southern Flounder

Diffuse dark spots 'and blotches

on pigmented side of body, ocellated

spots absent (Figure 1); gill rakers

on lower limb of outer arch 8-11

(usually 9-10); anal rays 63-73 &

(usually 65-71); dorsal rays 80-95

(usually 84-92); scales in straight

portion of lateral line 52-69

(usually 56-64); size relatively

large: attains a maximum standard

length (distance from snout to base

of tail) of 660 mm and a weight of

over 3 kg (Nail 1979).

Gulf Flounder

Three small, usually conspicuous,

ocellated spots on pigmented side of

body in a triangular pattern, with

the apex of the triangle pointing

posteriorly and the posteriormost

spot situated astride lateral line

(Figure 2); gill rakers on lower limb

of outer arch 9-12 (usually 10-11);

anal rays 53-63 (usually 56-61);

dorsal rays 71-85 (usually 75-81);

scales in straight portion of lateral

line 47-60 (usually 52-57); size

relatively small: attains a maximum

standard length (SL) of about 420 mm

.

2 d
GULF Of

MEXICO

CAPE

0

Q

‘6

PALM BEACH

FLORIDA

MIAMI

ROMAN

.

B

THOUSAND ISLAN ?

-1_

100

I

0 60 100

KILOMETERS

Figure 4. Areas of greatest abundance of southern flounder in south Florida.

3
9 -

b . . . .... :.:..::: ., :..

.:..::...: ,F,>. ._::_. P- LAKE\ _ _

<

OKEECHO’&?EE

h I

% ( y&:.‘~ji&b’l BEACH

ST. PETERSBURG

FLORIDA

0 50 100

KILOMETERS

Figure 5. Areas of greatest abundance of gulf flounder in south Florida.

4
CAPE ROMAN

0

Q

‘6

FLORIDA

THOUSAND ISLAND

PALM BEACH

MILES

4

0

-I

5 0 100

---. 1

0 50 100

KILOMETERS

MIAMI

Figure 6. Areas of greatest abundance of summer flounder in south Florida.

5
and a wei ght of about 1.7 kg (Nall

1979). Vick (1964) suggested a

maximum 1 ength of over 700 mm.

Summer Fl ounder

Five

usually

small ocellated spots

present on pigmented side of

body (becoming obscure in larger

specimens), with the first two and

last two situated on the lateral line

(Figure 3); gill rakers on lower limb

of outer arch 13-18 (usually 15 or

more); anal rays 61-73 (usually

66-70); dorsal rays 80-96 (usually

85-90); scales in straight portion

of lateral line 56-76 (usually

62-70); size relatively large:

attains a maximum standard length

(SL) of about 700 mm and a weight of

over 4.4 kg (Powell 1974).

Postlarvae

Postlarvae (i.e., individuals

that have metamorphosed into an

adult-like form) of the summer

flounder can be distinguished from

those of the southern and gulf

flounders by pigmentation pattern

(Deubler 1958). Summer flounder at

9-15 mm SL have a well-defined band

of black pigment along the border of

the anterior four-fifths of the dorsal fin and along the anterior twothirds of the anal fin (Figure 7);

pigment is lacking in these areas in

both the southern and gulf flounders

(Figure 8). Vertebral differences

are also useful for separating postlarval summer flounder from the other

two species: P. dentatus has 40-42

total vertebFae (usually 41), and

the other two species have 36-38,

usually 37. Gill rakers are not

sufficiently developed at this size

to be of aid in identification.

Postlarval southern and gulf flounders are difficult to separate at

small sizes, inasmuch as no pigmentary differences have been discovered

and vertebral counts for the two species are identical. Number of anal

Figure 7. Late postlarval

tion of summer flounder

1958).

pigmenta-

(Deubler

Figure 8. Late postlarval pigmentation of southern flounder (Deubler

1958).

rays is the most diagnostic character, but number of dorsal rays will

also separate most specimens (see

summary of adult characteristics).

REASON FOR INCLUSION IN SERIES

The three species of Paralichthys

are important components of both the

commercial and sport fishery catches,

but since they are combined in catch

statistics under the collective name

"fluke" (BCF 1964b-1968b; NMFS 1969b1985b), the exact importance of each

species cannot be ascertained. In

general, however, the summer flounder

is considered the most important of

the three species because of its

prominence in the sport and commercial fishery catches on the upper

Atlantic coast from Cape Hatteras

northward. Commercial fishery statistics from 1964 to 1985 indicate

6
that "fluke" have become an increasingly more important part of the

commercial catch in terms of both

dollar value and the amount of fish

taken.

LIFE HISTORY

Of the three species, the summer

flounder has received the greatest

attention with regard to studies of

its life history and ecology; Powell

(1974) and Rogers and Van Den Avyle

(1983) have provided the most complete summaries. T~PP and Hoff

(1972) summarized biological data

for the gulf flounder. Stokes (1977)

studied the life histories of both

the gulf and southern flounders in

the Aransas Bay area of Texas, and

Nall (1979) studied age and growth

of these two species in the northern

Gulf of Mexico. Powell (1974), in

his study of the summer flounder .in

North Carolina, also included considerable ecological data on the

southern flounder and limited data

for the gulf flounder.

Reproduction

Reproductive strategies appear to

be similar for the three species of

Paralichthys. Adults of each species

spend most of the year in bays and

estuaries, emigrating into deeper

offshore waters during fall and

winter as temperatures drop.

Spawning occurs at these times; ripe

individuals have been collected from

September to mid-April (Bigelow and

Schroeder 1953; Smith 1973) at

depths ranging from 20 to 136 m.

Spawning begins earlier at more

northerly latitudes (Smith 1973),

and occurs progressively later as

one proceeds southward. Eggs and

newly hatched larvae float at or

near the surface, and the developing

individuals are carried inshore by

winds and currents into nursery

areas, where further growth and

development take place. Appearance

of juvenile (i.e., late postlarval)

flounders in bays and estuaries

along the Atlantic coast usually

peaks when stratification and tidal

exchange ratios are at a yearly

maximum. Juveniles may move to the

surface at night and then be carried

by flood tides into tidal creeks

(Weinstein et al. 1980). In North

Carolina, newly metamorphosed

juvenile Paralichthys SPP. were

captured from December through April

i n estuarine nursery areas (Powell

and Schwartz 1977). Juveniles

remain in nursery areas until sexual

maturity is reached, and do not move

into offshore waters until just

prior to spawning (Powell and

Schwartz 1977).

Controversy exists with regard to

age at which sexual maturity is

reached, primarily because of

differences in interpretation of

aging techniques. Stokes (1977) and

Manooch (1984) indicated that both

southern and gulf flounders attain

sexual maturity at 2 years of age;

Powell (1974) reached a similar

conclusion for the southern flounder.

Powell (1974) and Manooch (1984) also

stated that the summer flounder does

not achieve sexual maturity until it

is 3 years old. However, Nall (1979)

reported that the southern flounder

does not reach sexual maturity until

at least 4 years of age, and that

sexual maturity of all individuals

was not achieved until they were

more than 6 years old.

Stokes (1977) reported adult

southern flounder leaving Aransas

Bay, Texas, for the Gulf of Mexico

from mid-October to mid-December.

Emigration peaked during mid-November

and seemed to be correlated with a

sudden drop (4-5OC) in temperature.

Males appeared to leave somewhat

earlier than females (Simmons and

Hoese 1959; Stokes 1977).

Southern flounder spawn from

September to April, although peak

7
activity is from November to January

(Gunter 1945). Spawning apparently

occurs at depths of 20-60 m (Benson

1982). Arnold et al. (1977), who

observed summer flounder spawning in

the laboratory, reported that

spawning females swam upward in the

water column and released their eggs,

which were immediately fertilized by

a single attending male.

Immigration of juvenile southern

flounder into Texas bays begins in

January and increases rapidly into

February, after which there is a

gradual increase in numbers of

individuals throughout the spring;

abundance peaks during mid-summer

(Stokes 1977). Immigration begins

when the average water temperature

is as low as 13.8oC, and peaks when

average water temperature is between

16.0 and 16.2oC. Adult summer

flounder return to Texas bays and

estuaries from February to April,

and remain there until the following

fall.

The only available figures on

fecundity are those of Arnold et al.

(1977), who indicated an average of

40,000 eggs per female in the l-3 kg

weight range. Nall

developing eggs in

(1;:;)) found

female

southern flounder over 6 years old,

but in only S-18% of females 4-6

years old. The smallest maturing

female reported by Nall (1979) was

256 mm SL (308 mm total leng;;nk;;;

of snout to tip of tail]).

(1984), who indicated that this

species becomes sexually mature at 2

years of age, gave the average total

length (TL) of 2 year-old individuals

as around 365 mm.

Reproduction in the gulf and

southern flounders is similar in most

respects. Gulf flounder spawn in the

Gulf of Mexico from mid-fall through

mid-winter, and Stokes (1977)

reported ripe adults leaving Aransas

Bay, Texas, from mid-October through

December. Spawning evidently occurs

offshore, and specimens with ripe

gonads have been collected at depths

of 20-40 m in the eastern Gulf of

Mexico from November through February

(Topp and Hoff 1972).

Larval gulf flounder appear in

the eastern Gulf of Mexico from

December to early March (Topp and

Hoff 1972), and juveniles are seen

in bays and estuaries in January

throughout their range, with peak

movement usually occurring in early

February (Reid 1954; S;;dnger and

Woodburn 1960; Tagatz Dudley

1961; Stokes 1977). Juvenile gulf

flounder, like southern flounder,

begin immigrating into Aransas Bay

when water temperatures reach 14-160C

(Stokes 1977). Topp and Hoff (1972)

reported spent females in Tampa Bay

in February.

No fecundity data are available

for the gulf flounder. Gonadal

examination by Nall (1979) indicated

that females mature at sizes as small

as 145 mm SL. Manooch (1984) stated

that sexual maturity in this species

is attained at two years of age. He

also indicated the average total

length of two-year-old individuals to

be around 350 mm, and the average

length of three-year-olds to be about

400 mm.

Most information on the summer

flounder is based on studies of

populations from Pamlico Sound, North

Carolina, northward. Smith (1973)

observed a seasonal progression in

spawning from north to' south. He

found that peak spawning at the

northern limits of its range occurred

in early September, spawning north of

Chesapeake Bay peaked in October, and

spawning south of Chesapeake Bay

peaked during November. Bigelow and

Schroeder (1953) reported collection

of a ripe female in mid-April off

Nantucket Is1 and, Massachusetts, but

this is unusual. During the 1971-72

season, spawning did not occur until

February around Cape Lookout, North

Carolina. Powell (I974), on the

basis of gonadal development,

8

* ’

d
-

reported that most summer flounder in

North Carolina waters south of Cape

Hatteras spawned from December

through February.

As is true of the other two

species, summer flounder spend the

warmer months in coastal embayments

and sometimes in nearshore shelf

waters, and migrate offshore during

the fall as waters cool. Rogers and

Van Den Avyl e (1983) reported

spawning over a broad depth range

(30-200 m). Individuals move into

deeper water near the peak of their

gonadal development cycle, with the

oldest and largest fish apparently

moving out first (Morse 1981). The

most important nursery areas are

located between Long Is1 and, New

York, and South Carolina (Powell

(1974) ; the heaviest concentrations

are in Virginia and North Carolina

(Poole 1966). Summer flounder less

than 280 mm TL are uncommon off New

England, which suggests that individuals found in those waters have

migrated there from the south and

that most are about three years old

(Lux and Nichy 1981).

Smith (1973) reported that eggs

found at or near the surface were

most common when bottom temperatures

were 12-19OC. Powell (1974) found

the most eggs in North Carolina

waters when bottom temperatures were

about 150C.

Prior to Smith's (1973) study,

it had generally been accepted that

currents transport larval summer

flounder from the north to major

nursery areas farther south, but it

now appears that, although eggs and

larvae may drift with the current,

this is less important than formerly

believed.

Female summer flounder appear to

reach sexual maturity at 300-330 mm

TL and males at 240-270 mm TL. The

smallest female examined by Morse

(1981) was 250 mm TL, and the

smallest mature male was 190 mm TL.

Early Developmental Stages

Bal on (1975) defined developmental stages larva,

juvenile, ad$t

egg,

and Transition

from egg to embryo occurs when the

egg membrane ruptures; the embryo

becomes a larva when the individual

switches from endogenous to exogenous

feeding; and the larva becomes a

juvenile upon metamorphosis to an

adult-like form. Inasmuch as all

three species spawn offshore, the

various life stages are adapted for

development in full-strength seawater. The onset of metamorphosis

in flatfishes appears to be more

closely related to environmental

temperature and/or size of the

individual than to age (Policansky

1982).

Although a detailed description

of early developmental stages exists

only for the summer flounder (Martin

and Drewry 1978: 157-163), one can

assume that the characters given

apply in large measure to the other

two species as well. Martin and

Drewry (1978) described the eggs of

the summer flounder as "small,

spherical, and transparent . . . with

a rigid shell," and measuring from

0.90 to 1.13 mm (mean = 1.02 mm).

The eggs are buoyant (thus, pelagic)

and contain a single oil globule in

the yolk (Figure 9).

Eggs of the summer flounder have

been observed to hatch in from 2 to 9

days (48 to 212 hrs) under laboratory

conditions, at temperatures from 21OC

down to 5OC (Johns and Howell 1980;

Johns et al. 1981). Lengths at

hatching were from 2.83 to 3.16 mm

(Johns et al. 1981). Although those

authors reported hatching at

temperatures as low as 5OC, they

also indicated that temperatures

below ll°C were lethal to larvae

during development. Yolk-sac

absorption (i.e., transition to

larval stage) in this species occurs

at about 3.6 mm, and Johns et al.

(1981) indicated that this size is

9
reached approximately 5.7 days after

hatching at ll.ZOC, or in 2.8 days at

21oc. At this point the eyes are

pigmented, the mouth functional, and

the digestive tract complete (Figure

10). Hildebrand and Cable (1930)

indicated that newly hatched embryos

of "Paralichthys spp." from Beaufort,

North Carolina (the summer flounder

is the dominant species in that area)

are about 2.5 mm long. At 7 mm the

larvae lose their symmetry and the

right eye begins to migrate dorsally.

Martin and Drewry (1978), however,

showed that this change in symmetry

occurs at a slightly larger size

(ca. 9.5 mm). At 10.5-11 mm, the

right eye becomes situated on the

ridge of the head (Figure ll), the

body becomes increasingly compressed,

and the left side of the body is

noticeably more pigmented than the

right side. At 16 mm, individuals

have a form and shape resembling the

adult, and pigmentation is almost

entirely restricted to the left

(i.e., eyed) side of the body. At

77 mm, the body is completely scaled

and has the characteristic form and

pigmentation of the adult.

Arnold et al. (1977) reported

that eggs of the southern flounder

hatched at 61 to 76 hrs under

laboratory conditions. Time at

which transition from embryo to

larva occurred was not indicated,

but time required for metamorphosis

to begin in the laboratory was 40 to

46 days after hatching (at 8 to 11

mm), and this process was completed

in 50 to 51 days.

4 mm NL

Figure 9. Egg development and yolksac larva of summer flounder, from

less than 32 h after fertilization

to 75 h after fertilization. Lengths

expressed in standard length (SL) or

notochord length (tip of snout to

end of notochord) (NL) (Martin and

Drewry 1978).

Figure 10. Yolk-sac larva to larval

stages of summer flounder: (A) 12 h

after hatching, (B) 96 h after hatching, and (C-E) subsequent stages

(Martin and Drewry 1978).

10
Figure 11. Larval stages of summer

flounder, showing transition of eyes

from symmetrical to asymmetrical

position (Martin and Drewry 1978).

Migration and Movement of Adults

Seasonal inshore-offshore

movements of adult Paralichthys are

related to spawning activities, as

discussed earlier. Tagging studies

of summer flounder show that latitudinal movement occurs along the

Atlantic coast. Of a total of 6,679

individuals tagged off New Jersey

during 1960-67, 2 were recaptured

south

Carolina Of(MuC,Zki

Hatteras, North

1970). Poole

(1962) reported 1 return from below

Cape Hatteras out of 5,845 individuals tagged in New York waters

during 1956-59. Lux and Nichy

(1981) reported 1 return (out of

2,839) in early 1963 from off

southern Maryland; the individual

had been tagged in New York waters

the preceding September. Lux and

Nichy (1981) and Rogers and Van Den

Avyle (1983), however, said that in

general tagging studies in the

Middle Atlantic Bight (i.e., from

Cape Hatteras northward) indicated

an overall movement of this species

toward the northern limits of the

Bight as the fish grow older.

The only published results of

tagging studies involving the

southern flounder are those by Stokes

(1977) from Texas, who reported 28

returns out of a total of 1,298

individuals

early 1974

taggedlatL2.2%) between

and 1975. He

reported some movement between and

within Texas bays, although no

consistent patterns were evident.

Returns showed movement of from 0 to

18.2 km over periods of 3 to 212

days; the most rapid movement was

9.3 km in 3 days. One individual

tagged in November 1973, in Aransas

Bay, was recovered 1 year later 451

km to the east.

The only tagging study of gulf

flounder was by Stokes (1977), who

reported no returns out of a total

of 33 individuals tagged.

Although the above data seem to

indicate more extensive movements of

the summer flounder than the other

two species, this may be, at least

in part, a result of the greater

number of summer flounder tagged, as

well as the longer period of time

during which studies on the summer

flounder were carried out.

Subpopulations

Analysis of morphometric and

meristic characters in 1,214

specimens of summer flounder from

New York to central Florida indicate

two distinct subpopulations, one in

the Middle Atlantic Bight north of

Cape Hatteras, North Carolina, and

the other in the South Atlantic

Bight (Wilk et al. 1980). Discriminant analysis coefficients indicate

these subpopulations are separable

at a level of 93%. These results

are partly confirmed by tagging

11
studies by Poole (1962) and Murawski

(I97D), who found little evidence of

movement of individuals between

these two areas, as well as Smith's

(1973) studies of distribution

patterns of eggs and larvae. Smith

(1973) had also suggested that the

subpopulation in the Middle Atlantic

Bight could be further subdivided,

with one group occurring in New York

and New Jersey and the other from

Delaware Bay to Cape Hatteras; but

Wilk et al. (1980) could neither

confirm nor deny this hypothesis on

the basis of their work.

There is insufficient data to

indicate whether or not distinct

subpopulations of southern and gulf

flounders exist; however, the wide

distributional break of the southern

flounder around the tip of peninsular

Florida (Figure 4) suggests that

this is a reasonable possibility.

GROWTH CHARACTERISTICS

Almost all age-growth studies of

Paralichthys have used otoliths to

determine age. Analyses of yearly

size classes, even at small sizes,

have been shown to be of limited

value because of variable individual

growth rates and protracted spawning

seasons. Body lengths may be

expressed either as standard length

or total length. Sometimes method

of measurement is not indicated,

although in such cases one can

usually assume this to be total

length. Since the tail makes

about 17% of the total body lengtzp

one can substract this percentage,

when necessary, to obtain approximate

standard length. Sex of individuals

analyzed is not always indicated,

despite evidence that Paralichthys

females reach a larger size than

males.

Controversy exists regarding

results of various otolith aging

studies on the species of Paralichthys. Different investigators

have ' . ..variously indicated the

first 'annulus' ’ the summer

flounder to form at iies II through

VII, indicating that length-at-age

information is subject to considerable error" (Rogers and Van Den Avyle

1983). Poole (1961) and Powell

(I974), working on New York and North

Carolina populations, respectively,

determined that the first opaque

ring on the otoliths of summer

flounder was a valid first annulus.

Poole also concluded that the species

attains a maximum age of no more than

5 years, but he did not attempt to

estimate maximum longevity. Eldri&;

(I962), Smith (1969)) Daiber

Smith (1969), and Smith and Daiber

(1977) determined that the first

distinct opaque ring does not represent the first annulus, and concluded

that this species lives as long as 8

or 9 years. Smith et al. (1981)

concluded that estimates of greater

longevity are more likely correct.

Similar controversy results from

the age-growth studies on southern

flounder by Stokes (1977) and Nall

(1979) on Texas and northern Gulf of

Mexico populations, respectively.

Stokes concluded that this species

lives a maximum of 5 years, as

opposed to the 9 (occasionally 10)

years projected by Nall (1979). The

only age-growth studies on the gulf

flounder were also conducted by

Stokes (1977), who indicated that

they live a maximum of 3 years.

Assuming that Stokes (1977) was

consistent in his aging techniques

for southern and gulf flounder, one

may presume that the latter species

has the shorter life span of the

two, although it may be longer than

that indicated by Stokes.

Manooch (1984) summarized agegrowth data for all three species.

He indicated a maximum age of 9

years for the summer flounder, and

listed the following average yearly

total lengths in mm for age groups

I-IX (females only): 215, 288, 377,

12
k 428, 488, 511, 531, 564, and 597

mm. These data are comparable to

those provided for females of this

species by Eldridge (1962) and Smith

and Daiberyea!;;77), who gave the

following total

lengths (also in mm~vef~~g~ge groups

I-VII: 170, 250, 332, 377, 415, 446,

and 456 mm. As indicated from the

above, females not only reach

larger size but also apparently livi

longer, inasmuch as all individuals

examined by Eldridge (1962) that

were over 7 years of age were

females. In all studies but one it

was concluded that females live 1

year longer than males; the exception

was reported by Smith (1969), who

determined that male summer flounder

achieve a maximum age of only 5

years, as opposed to 8 for females.

Daiber and Smith (1969) found

the respective maximum sizes for

female and male summer flounder from

Delaware to be 661 and 517 mm TL.

Powell (1974) found that only two

i

individuals from North Carolina (out

of a total of 1,029) exceeded 650 mm

TL, with the largest being 750 mm.

Poole (1966) determined the maximum

size of females from New York to be

around 800 mm TL and 5.5 kg, and for

males 600 mm TL and 2.2 kg. DeSylva

(1965) reported that although this

species occasionally reaches 11-13.6

kg, a weight of 7 kg is unusual; he

indicated that most adults weigh

between 0.9-2.3 kg. Powell (1974)

presented a graph showing lengthweight relationships based on 1029

specimens (sexes combined) from North

Carolina (Figure 12).

Manooch (1984) indicated life

spans of only 5 and 3 years for the

southern and gulf flounder, respectively. This information is in accord

with, and may partly have been based

upon, Stokes' (1977) studies from

Texas. However, Nall (1979), based

on examination of 152 specimens from

the northern Gulf of Mexico, calculated a life span of 9 (occasionally

10) years for the southern flounder,

4.w I

LOG W = -5.25363 + 3.0989 LOG L

R = 0.995

Figure 12. Length-weight relationship with fitted curve for summer

flounder. Weight expressed *

grams; length in total length (PoweiC

1974).

and provided the following average

standard lengths in mm (sexes combined) for each year of life approximate converted (total lengths indicated in parentheses): Age 0 = 63

(76)> I = 102 (122), II = 145.5

[;;;I, III = 190.5 (250), IV = 230.5

V = 272 (327), VI = 320 (384),

VII =‘35!.5 (423), VIII = 382 (460).

Stokes (1977), in studies of Texas

populations of the southern flounder,

found differences in size and life

span between males and females

similar to those reported earlier

for the summer flounder. He reported

that females live up to 5 years and

reach a total length of up to 620 mm,

whereas males live only up to 3 years

and reach a maximum total length of

320 mm. Although Stokes may have

3
underestimated the overall life span

of this species, his data clearly

indicate that females live longer

and attain a larger size than males.

The largest individual southern

flounder (620 mm TL) reported by

Stokes (1977) is slightly larger

than that examined by Nall (1979)

(493 mm SL, or ca. 595 mm TL).

Ginsburg (1952), however, reported a

maximum size for this species of 630

mm SL (= 762 mm TL). Nall (1979)

presented a graph showing lengthweight relationships based on 152

specimens (sexes combined; Figure 13).

Stokes (1977) conducted the only

age-growth study of the gulf

flounder, although Nail's (1979)

study contained limited data. Both

studies were conducted in conjunction

100 200 ml 400 5

STANDARD LENGTH IN MM

Figure 13. Length-weight relationship with fitted curve for southern

flounder. Weight expressed in grams;

length in standard length (Nail

1979).

with work on the southern flounder, * >

which is much more common in the

respective study areas (Texas and

the northern Gulf of Mexico); the

small number of specimens available

to Nall (33) precluded his attempting

any aging estimates. Stokes (1977)

concluded, based on a total of 123

specimens, that female and male gulf

flounder live only 3 and 2 years,

respectively, and these figures were

repeated by Manooch (1984). Although

the gulf flounder may live longer

than indicated by Stokes, his data

nevertheless strongly suggest a

shorter life span for this species

as compared to both the southern and

summer flounders. The largest female

and male gulf flounders examined by

Stokes were 420 and 290 mm TL,

respectively. This is substantially

smaller than(s;;e

individual

710 mm .TL.(5 kg)

not indicated)

reported by Vick (1964) from St.

Andrews Bay, Florida. The markedly

greater size of Vick's specimen

suggests the possibility of species

misidentification (most likely with

the southern flounder), and thus this

record requires confirmation. Nall

(1979) presented a graph showing

length-weight relationships of gulf

flounder, based on 33 specimens

(sexes combined) (Figure 14).

There is some evidence that

southern flounder from different

areas grow at different rates, independent of differing interpretations

.

%ris?~~g1979. Nall 1979)

techniques (Etzo:Ris ;I;

be due to comb)inations of *differences

involving genetic stock, prey availability, temperature and salinity

(DeublerP,~~rE$); Stickney and White

1973; and Kjelson 1975;

Laurence 1977).

ECOLOGICAL ROLE

Food and Feeding

The three species of Paralichthys

under consideration consume animal

1 4
1W 200 300 400 500

STANDARD LENGTH IN MM

Figure 14. Length-weight relation-

$

ship with

flounder.

fitted curve for gulf

Weight expressed ’

grams; length

(Nall 1979).

in standard lens::

matter throughout life. Postlarvae

feed on zooplankton and adu'lts feed

on benthic and pelagic fishes, as

well as crustaceans.

Peters and Angelovic (1971) reared

postlarval summer flounder on a diet

of zooDlankton (mostlv CODeDOdS) and

Artemia' nauplii: Deubler' (i958)

raised postlarvae of summer,

southern, and gulf flounder "to a

definitive size" on brine shrimp

(Artemia), white worms (Enchytraeus);

and cut shrimp (Penaeus). Lasswell

et al. (1977) found that

metamorphosed -southern

newly

flounder feed

readily upon rotifers (Branchionus

plicatilis). Houde and Taniguchi

(1979) determined that the planktonic

larvae of many fishes, including

species of Paralichthys, feed on a

wide variety of animal organisms,

with copepod nauplii predominating.

Plankton density is an important

factor in larval survival, particularly since it affects the growth

rate of the individual and length of

the larval period, which is the time

during which these fish are most

vulnerable to predation (Houde and

Schekter 1980).

Reid (1954) reported that gulf

flounder under 45 mm TL feed

primarily on amphipods and other

small crustaceans; above this size

they begin to feed on fish, which

subsequently become the main item in

their diet. Stokes (1977) found

that, numerically, 95% of the food

items of juvenile southern flounder

(lo-150 mm TL) from Texas consists

of invertebrates. Juvenile southern

flounder over 80 mm TL consume

progressively larger food items as

the fish increases in size, but

there is no indication that large

adult flounders eat larger prey than

subadults (Darnell 1958; Fox and

White 1969). Powell and Schwartz

(1979) compared the year-long diets

of young (100-200 mm TL) summer and

southern flounder from Pamlico Sound,

North Carolina (Figure 15). A much

higher percentage of empty stomachs

was noted during the winter months.

Powell and Schwartz (1979) found the

two species to feed on basically the

same food items. Fish and mysids

(malacostracan crustaceans) formed

the bulk of their diet at all

seasons; however, they found the

relative percentages of food items

to be consistently different, with

the southern flounder feeding more

heavily on fish. They considered

that this most likely resulted from

differing food availability in the

different habitats occupied by the

two species (i.e., the summer

flounder prefers higher salinities

and a sand bottom, whereas the

southern flounder occurs in lowersalinity water over a mud-silt-clay

bottom); however, they did not discount the possibility of selective

1 5
Figure 15. Percentage of volume and

(in parentheses) percentage of occurrence of food items in seasonal diet

of (100-200 mm TL) summer

floun~~~n~nd southern flounder from

Pamlico Sound, North Carolina.

Numbers above each bar graph indicate

number of stomachs with food/total

number of stomachs examined (Powell

and Schwartz 1979).

SEASON

feeding, since Williams (1972) has

shown that the greatest densities of

mysids in Pamlico Sound are in those

areas where southern flounder predominate.

Larger southern and gulf flounder

feed proportionally more on fish than

on other organisms (Reid 1954;

Springer and Woodburn 1960; Topp and

Hoff 1972; Stokes 1977; Powell and

Schwartz 1979). Stokes (1977) found

that fish comprise more than 70% of

the food items in individuals over

150 mm TL; penaeid shrimp and blue

crabs are the most frequently

consumed invertebrates. Genera or

~~~~~eSin

of fishes that have been

the diet of both southern

and gulf flounder include mullet

(Mugil spp.), menhaden (Brevoortia

SPP.), Atlantic croaker (Micropogonias undulatus), and pinfish

(Lagodon rhomboides) (Reid 1954;

Darnell 1958; Springer and Woodburn

1960; Fox and White 1969; Topp and

Hoff 1972; Stokes 1977; Overstreet

and Heard 1982). Frequency of

occurrence of different fish species

in the diet appears to depend more

on local and/or seasonal prey

abundance than on specific prey

selection (Darnell 1958; Fox and

White 1969).

Feeding behavior has only been

described for the summer flounder,

but presumably is similar for all

three species. The summer flounder

is primarily a diurnal feeder that

can capture its prey equally well on

the bottom or in the water column

(Olla et al. 1972; Powell and

Schwartz 1979). Although it may

bury itself in bottom sediments, it

does not ambush passing prey, but

rather stalks its quarry along the

bottom before striking at speeds of

40 to 50 cm/set (Olla et al. 1972).

ENVIRONMENTAL REQUIREMENTS

Substrate

The three species of Paralichthys

under discussion apparently prefer

specific substrates. Most studies

indicate that the summer flounder

prefers a hard and/or sandy substrate

(Hildebrand and Schroeder 1928;

Bigelow and Schroeder 1953; Powell

and Schwartz 1979), as does the gulf

flounder (Ginsburg 1952; Stokes 1977;

Nall 1979), but the southern flounder

is most abundant on soft bottoms

comprised of rich organic mud, clay,

or silt (Ginsburg 1952; Stokes 1977;

Nall 1979; Powell and Schwartz 1979).

The contrasting relative abundance

of southern and gulf flounder in the

eastern Gulf of Mexico may reflect

these habitat preferences, inasmuch

the western gulf' (where the

&thern flounder predominates) ’

substantially muddier, on t;l:

average, than the eastern gulf

(Lynch 1954).

16
kw Tabb and Manning (1961) reported

that southern flounder from southwestern Florida occur over shell and

firm marl bottoms, but Topp and Hoff

(1972) questioned their

? :

species

identifications, since the area where

these observations were made is

outside the known geographic range

of this species. Dahlberg and Odum

,

(1970) reported southern flounder in

Georgia from bays with primarily

sand bottoms. Springer and Woodburn

r (1960) collected gulf flounder over a

wide variety of habitats in the

Tampa Bay area of Florida. Moe and

Martin (1965) collected a few gulf

flounder near rocky offshore reefs,

and this species occasionally has

been found around coral reefs in the

extreme western Bahamas (Bohlke and

Chaplin 1968). Nall (1979), based

on observations of 152 specimens,

never found southern flounder over an

exclusively sand bottom, but noted I

that gulf flounder were somewhat

less specific with regard to bottom

type. Of 33 specimens analyzed, 12

&

were collected over a sand bottom, 16

came from a combination sand-mud

bottom, and 5 were from a strictly

mud bottom.

Salinity

Adult southern flounder, in

contrast to adult gulf and summer

flounder, are highly euryhaline, as

indicated by their frequent occurrence i n rivers (Ross 1980).

Analyses of collections of adult

southern and gulf flounders from a

wide geographic area (Florida to

Texas) usually indicate a strong

preference by the former species for

salinities less than 20 ppt (Gunter

1945; Tagatz 1968; Stokes 1977) and

by the latter species for salinities

greater than this (Reid 1954;

Springer and Woodburn 1960; Stokes

1977). Perret (1971), however,

reported samples of southern flounder

(totaling about 800 individuals)

taken from Louisiana estuaries to be

equally distributed over salinities

ranging from 0 to slightly over 30

I$' Powell (1974), in his analysis

the relative numbers of adult

southern and summer flounder in a

North Carolina estuary, found an

inverse relationship between the two

species with regard to salinity;

southern flounder predominated at

salinities up to 11 ppt (85% of the

total), but above 11 ppt the summer

flounder predominated (65% of the

total). Another sharp change in

relative percentages of individuals

of these two species was noted as

salinity increased from 17 to 18

PPt; at this point the relative

abundance of summer flounder

increased from 65% to 94%.

Juvenile southern flounder appear

to be more strongly euryhaline than

juveniles of the other two species,

and have been shown to survive abrupt

transfer from nearly full-strength

seawater (30 PPt) to freshwater

(Deubler 1960). Although juvenile

southern flounder have been collected

from North Carolina estuaries at

salinities ranging from 0.2 to 35.0

ppt (Powell and Schwartz 1977), it

appears that a change in salinity

tolerance occurs during development

from early postlarval to a more

advanced postlarval stage. Early

postlarvae of this species grow most

rapidly at higher salinities (ca. 30

ppt), but individuals of this size

(0.1 g) are not very tolerant of

extremely low salinities; however,

advanced postlarvae do best at

salinities of 5-15 ppt (Stickney and

White 1973). Deubler and White

(1962) showed that advanced postlarval summer flounder, by contrast,

exhibit the greatest percentage

weight gain at salinities between 20

and 30 ppt. The differing salinity

levels at which optimal development

of southern and summer flounder

occurs during laboratory experiments

reflect the different natural

environmental conditions under which

these two species are found.

,L 1 7
Powell and Schwartz (1977)

reported collecting juvenile gulf

flounder from North Carolina estuaries at salinities ranging from 6 to

35 ppt, whereas Williams and Deubler

(1968) reported taking them only over

a sal;;:y range from 22 to 35 ppt.

In cases, however, it was

indicated that greatest abundance

was found near mouths of estuaries,

where salinities were highest.

Hickman (1968) found that adult

southern flounder exhibit seasonal

changes in osmoregulatory processes

that correspond to spawning

migrations between estuarine and

offshore waters.

Temperature

Adults of the three species of

Paralichthys under discussion have

been reported over 'comparable

temperature ranges. Perret (1971)

reported collecting adult southern

flounders from Louisiana estuaries

over a temperature range of 5.0-

34.9OC (41.0-94.8oF). These figures

represent both the minimum and

maximum temperatures reported for

adults of this species throughout its

range, and exceed the temperature

ranges reported by Barrett et al.

(1978) from Louisiana, and by Gunter

(1945) and Stokes (1977) from Texas.

All temperature data on adult gulf

flounders are based on observations

from Florida, and range from 8.3OC

(46.9oF) (Reid 1954) to 32.5OC

(90.5OF) (Springer and Woodburn

1960). Powell (1974) reported the

minimum and maximum temperatures at

which summer flounders were collected

in Pamlico Sound, North Carolina, to

range from 7oC (44.6OF) in February

to 290C (84.4OF) in July and August.

Stokes (1977) found that adults

of both the southern and gulf

flounders left Aransas Bay, Texas,

during the period when the mean2;a$

temperature dropped from

(73.4oF) in October to 14:l°C

(57.4oF) in December. Maximum

emigration often (though not always)

coincided with the passage of cold

fronts, when sudden drops in temperature (up to 4-5oC) occurred.

Williams and Deubler (1968)

reported the capture of juvenile

southern and gulf flounders in

Atlantic estuaries at water temperatures as low as 2-4°cfo~~~.6-39.20F),

and Gunter (1945) juvenile

southern flounder (17-40 mm) in Texas

estua;;eio;t temperatures from 14.5

to (58.1-70.9oF).

(1977) 'found that juvenile sol%%

and gulf flounders began to immigrate

into Texas estuaries from the Gulf

of Mexico at water temperatures as

low as 13.8OC' (56.8OF), but peak

movement occurred between 16.0 and

16.2OC (60.8-61.2OF). Williams and

Deubler (1968) reported the capture

of juvenile summer flounder over a

temperature range of 2-22OC (35.6-

71.6OF); most individuals were found

in the 8-160C (46.4-60.8OF) temperature range.

Temperature is important in the

life histories of these species, and

affects such things as time of

spawning, movement of adults and

larvae into different habitats,

availability of preferred food

items, maximal efficiency of food

conversion, and rapidity of growth.

Vegetation

Aquatic vegetation does not

appear important to the basic ecology

of adult Paralichthys, but is

utilized by juveniles. Adams (1976)

and Orth and Heck (1980) reported

that juvenile summer flounder occur

in eelgrass (Zostera marina) beds

during daylight hours, either to take

advantage of the cover afforded or to

feed on small fish and invertebrates

that congregate there. Stokes

(1977) found juveniles of both

southern and gulf flounders to be

most abundant in those areas of

1 8
L estuaries where dense patches of

shoal grass (Diplanthera wrightii)

were present and covered 30% to 60%

of the total area. Reid (1954)

reported juvenile gulf flounder to

be abundant on shallow grass flats

around Cedar Keys, on the gulf coast

of northern peninsular Florida.

Dissolved oxygen

Deubler and Posner's (1963)

laboratory study of juvenile southern

flounder apparently is the only work

published on oxygen requirements of

any Paralichthys species. They found

that juvenile southern flounder

actively moved into more highly

oxygenated water when the dissolved

oxygen concentration fell below 3.7

mg/liter. Although they noted

increased general activity with an

increase in water temperature, there

was no increase in sensitivity to

oxygen depletion at temperature

levels of 6.1°, 14.4O, and 25.301:

b

(43.0°, 57.90, and 77.5 OF, respectively).

FISHERY

Quality and Value of Commercial

Fishery

The three species of Paralichthys

under discussion are highly prized

North American food fishes; the

relative importance of each species

greatest in the area of its

iyghest abundance. From late spring

into the fall most commercial catches

of these fish are made by shrimp

trawlers fishing close inshore or in

estuaries, and smaller numbers are

caught by individual fishermen

"gigging" (i.e., spearing) in the

shallows at night. Lesser numbers of

summer flounder are caught at this

time in fyke nets, weirs, traps, and

pound nets (Manooch 1984). During

the winter months, most are caught by

vessels fishing with otter trawls in

deeper waters offshore.

k

The three species are lumped

together (either as "fluke"

"flounder") in Federal commerciif

;;",;h statistics (BCF 1939a-1968a;

1969a-1977a; BCF 1964b-1968b;

NMFS 1969b-1985b). In some cases

they were distinguished from other

commercially important flatfish

species living along the upper

Atlantic coast (i.e., north of North

Carolina), such as "blackback," or

winter flounder (Pseudopleuronectes

americanus) and yellowtail flounder

(Limanda ferruginea), whereas in

other cases these species were

combined *

Dnfortunateliy

catch statistics.

in those cases in

which the above taxa were separated,

catch statistics were combined for

the entire Atlantic coast and Gulf of

Mexico (BCF 1964b-1968b; NMFS 1969b1985b); alternately, when this broad

geographic region was broken down

into smaller subregions, these taxa

were combined (BCF 1939a-1968a; NMFS

1969a-1977a). This greatly complicates interpretation of catch statistics from the upper Atlantic coast,

and allows meaningful comparison

only for the lower Atlantic coast

and Gulf of Mexico.

For the South Atlantic region,

the total poundage of flounders

remained relatively low until 1945,

ranging from 132,000 lb in 1918 to

1.5 million lb in 1936 (BCF 1939a1968a). In 1945, there was an

increase to about 2.1 million lb, a

circumstance likely related in part

to cessation of the war. Catches

dropped during the late 1950's, but

subsequently increased and reached a

peak of slightly over 5.1 million lb

in 1965, for a total value of just

over 1 million dollars. By 1977 (the

last year for which data are

available for this specific area),

the total catch had risen to 11.4

million lb, for a total value of 5.1

million dollars. (Keep in mind that

dollar values are biased by inflation.) Over 90% of the "flounder"

catch for the South Atlantic area

comes from North Carolina, and can

.9
be attributed in large degree to the

substantially greater abundance of

summer flounder in that area, as

opposed to farther south.

Total catches of "flounder" from

the Gulf of Mexico area are substantially less, but show a similar

upward trend. Commercial catches

ranged from a low of 192,000 lb in

1888 to over 1.1 million lb in 1945,

and had increased slightly to 1.2

million lb by 1965, for a value of

$231,000. By 1977 the total catch

amounted to slightly over 1.5 million

lb, for a value of $561,000. In

contrast to the situation in the

South Atlantic area, no one State

bordering the Gulf of Mexico was

dominant in terms of the number of

pounds harvested.

The relative importance of

"flounder" in commercial catches has

increased substantially in comparison

to most other commercially important

marine food species. Prior to 1945,

for example, catches of "flounder"

along the South Atlantic coast were

substantially less than those for

"croakers" or "drums" (several species, but predominantly the Atlantic

croaker), bluefish, king mackerel,

Spanish mackerel, kingfish or king

whiting, mullet (mostly striped

mullet), sea trout, and spot. By

the total poundage of "flouniz?'exceeded the total for ;;cig7;f

the above except mullet.

the total poundage exceeded that fo;

each of the other species (most by a

substantial amount) except croakers,

and the total dollar value was

greater than for each of the above

in both 1965 and 1977 (comparative

dollar values are not available

prior to 1945).

Recent total poundage and dollar

value figures for "flounder" from

the Gulf of Mexico are well below

those for a number of other commercial fish species, but nevertheless

show an upward trend comparable to

that seen for the South Atlantic

coast.

Commercial catch data for

flounder from Florida during the

period 1964-1983 (Fla. Dep. Nat.

Res., unpub. Florida landings) show

results somewhat different from those

given above. Although total poundage

of flounder increased during this

period, from a low of 336,600 lb in

1967 to a high of 775,400 lb in

1982, the overall importance of

flounder in relation to other edible

commercial marine species in Florida

has stayed about the same. It ranks

about 15th behind such fishes as

groupers (several species, the most

important of whic,h is the red

grouper); several species of snapper,

including mangrove, red, and

yellowtail; Spanish mackerel; king

mackerel; striped mullet; sheepshead;

Florida pompano; jack crevalle;

spotted seatrout; king whiting; spot;

and several species of "croakers" or

"drums," such as Atlantic croaker and

redfish.

Data from Florida also include a

breakdown of commercial catches of

flounder according to location (i.e.,

Atlantic and Gulf of Mexico coasts).

These show consistently higher

catches for the gulf coast. In 1969,

the catch for the Atlantic coast was

less than 50% of that for the gulf

coast (120,000 vs. 268,600 lb), but

for most years the relative percentages ranged above 70%, with a high of

88% in 1981 (276,900 vs. 313,200

lb). Extremes in yields for the

Atlantic coast ranged from 120,000

lb in 1969 to 322,500 lb in 1979;

for the gulf coast these figures

ranged from 182,800 lb in 1967 to

404,200 lb in 1979.

Sport Fishery

Flounder are caught by sport

fishermen using various techniques,

such as still fishing, drift fishing,

casting from shore, and angling from

piers and banks using live, fresh,

or frozen baits cast 6 to 18 inches

above the bottom (Wisner 1965).

20
Another popular method for catching

these fish in some areas is by

"gigging" at night in shallow water,

using a long-handled, three-pronged

spear and a torch or flashlight

(DeSylva 1965). Sport fishing

usually begins in the spring (when

the fish return from deeper waters

offshore, where they have spent the

winter), and continues into the fall.

Sport catch statistics for the

Atlantic and gulf coasts (NMFS 1969b1985b) are more informative than commercial catch statistics because

individual species are identified.

These data indicate that the summer

flounder is one of the most important

game fishes, in terms of numbers

caught, along the mid-Atlantic coast

between Cape Hatteras and Cape Cod,

together with winter flounder, bluefish, white perch, spot, scup, and

various searobins. In 1980, it ranked

second only to bluefish, but in 1979

it ranked about fifth in number.

Based on average size of individuals

caught, it would rank well ahead of

all of the above except winter

flounder and bluefish. Along the

south Atlantic and gulf coasts,

however, the numbers of flounder

caught are well below those for many

other sport species.

2 1

LITERATURE CITED

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eelgrass, Zostera marina (L.), fish

communities. I . Structural

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22: 269-291.

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Lasswell. 1977. Laboratory spawning and larval rearing of red drum

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Balon, E. K. 1975. Terminology of

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Barrett, B. B., J. L. Merrell, T. P.

Morrison, M. C. Gillespie, E. J.

Ralph, and J. F. Burdon. 1978. A

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.

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

1953. Fishes of the Gulf of Maine.

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Deubler, E. E., Jr. 1960. Salinity

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Influence of salin;;;

of postlarvae of

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finfish

A Mississippi m,;i;ne

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Feeding habits of the southern

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Circ. 263. 47 pp.

Hickman, C. P., Jr. 1968. Glomerular filtration and urine flow in

the euryhaline southern flounder,

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427-437.

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1930. Development and life

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43:1-366.

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1980. Feeding by marine fish

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Johns, D. M., and W. H. Howell.

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24
k Lasswell, 3. L., G. Ganza, and W. H.

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b

Lynch, S. A. 1954. Geology of the

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PP.

Moe, M. A., Jr., and G. T. Martin.

1965. Fishes taken on monthly

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Tampa Bay area. Tulane Stud.

zoo1 . 12: 129-151.

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the summer flounder, Paralichthys

t;;t;;;s (L.). J. Fish Biol. 19:

.

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tagging

flounder,

experiments of summer

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from 1960 to 1967. N. -J. Dep.

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and

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25
Peters, D. S., and J. W. Angelovic.

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26
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.

Wilk, S. W., W. G. Smith, D. E.

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penaeid

Chesapeake Sci. 9:27-41.

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Holt, Rinehart and Winston, New

York.

27
50272 -101

REPORT DOCUMENTATION 1. REWRT NO. xl *.

I 3. RM,plcnt’l Actor,.,” No.

PAGE i Biological Report 82(11.54) , 4. Title and Subtitle ----I-S. Rwort cJ*tc

Species Profiles: Life Histories and Environmental Requirements

of Coastal Fishes and Invertebrates (South Florida)--Southern,

July 1986

Gulf, and Summer Flounders b

6.

7. Author(r)

Carter R. Gilbert

S. Pwformong Orcanization Rcpt. No.

i. Pwforming Organization Name and Address

Florida State Museum

University of Florida

Gainesville, FL 32611

10. PmjectlT~sklWark Unit No.

12. Sponsoring Organization Name and Address

11. ContrscUC) or Grant(G) NO.

0

(Gl

National Wetlands Research Center U.S. Army Corps of Engineers

Fish and Wildlife Service Waterways Experiment Station

U.S. Department of the Interior P.O. Box 631

Washington, DC 20240 Vicksburg, MS 39180

13. Tyw of R*port 6 Period Cowmc

14.

IS. Supplcmentwy Notes

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

l& Abstrut (Limit: 200 words)

Species profiles are literature summaries of the taxonomy, morphology, range, life history

and environmental requirements of coastal species. The southern, gulf, and summer flounde

live most of their lives in or near estuaries. Adults migrate into offshore waters during

fall and winter, where spawning occurs from September to April. Eggs and newly-hatched

larvae are carried inshore into estuaries, where further growth takes place. Age at

sexual maturity for the three species has been estimated from 2 to 4 years, and maximum longevity from 3 to 10 years. Females apparently live slightly longer than

males. Southern and summer flounders are estimated to live slightly longer than the

smaller gulf flounder. Postlarvae eat mostly zooplankton, and larger individuals feed on

fish and crustaceans. The summer and gulf flounders prefer a hard and/or sandy substrate,

whereas the southern flounder is more common in a soft bottom of rich organic mud, clay,

or silt. The southern flounder, unlike the other two species, is highly euryhaline, and

frequently occurs in fresh water. Commercial catch statistics lump the three species

together under the name "flounder." Peak commercial catch in the Gulf of Mexico (in 1977)

was 1.5 million lb, for a vaiue of $561,000; peak catch in the south Atlantic region

(also in 1977) was 11.4 million lb, for a value of $5,100,000.

17. Document Analysis a. bcsccrigton

Estuaries Fishes

Fisheries Flatfishes

Salinity Temperature

Feeding Habits Life Cycles

Growth

b. IdwdiR~n/Opcn.Endcd Twms

Southern flounder Gulf flounder Summer flounder

Paralichthys lethostigma Paralichthys albiguttq Paralichthys dentatus

Temperature requirements Spawning Commercial importance

Life history Habitat requirements

c. COSATI Field/Group

lb Availability Statement

Unlimited

21. No. of Pages

27 --

?2. price

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

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