(DRAFT) - Taxonomy
Species flounder, southern
Species Id M010021
Date 27 AUG 96
TAXONOMY
NAME - flounder, southern
OTHER COMMON NAMES - flounder, mud flounder, doormat and halibut
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Chordata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Pleuronectiformes,
FAMILY AND SUBFAMILY - Bothidae,
GENUS AND SUBGENUS - Paralichthys,
SPECIES AND SSP - lethostigma,
SCIENTIFIC NAME - Paralichthys lethostigma
AUTHORITY - Jordan and Gilbert
TAXONOMY REFERENCES - 77
COMMENTS ON TAXONOMY -
Other common names are Flounder, mud flounder, doormat, and halibut.*77*
Taxonomy - 1 (DRAFT) - Status
Species flounder, southern
Species Id M010021
Date 27 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Commercial/consumption
REFERENCES FOR STATUS - 77
COMMENTS ON STATUS -
The southern flounder is a valuable sport and commercial fish along the gulf
coast. Sport fishing is done by hook and line and by gigging. Most of the
commercial catch is incidental to the catch by shrimp trawlers. The
southern flounder is "one of the most sought after and prized fish in the
area and is recognized for its fine flavor."*77*
Status - 1 (DRAFT) - Distribution
Species flounder, southern
Species Id M010021
Date 27 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Estuarine
Habitat Associations - 1 (DRAFT) - Food Habits
Species flounder, southern
Species Id M010021
Date 27 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 77
LIFESTAGE FOOD FOOD PART
Juvenile Invertebrate Cordates See Comments
Adult Osteichthyes See Comments
REFERENCES FOR ADULT FOOD - 77
REFERENCES FOR JUVENILE FOOD - 77
COMMENTS ON FOOD -
Small southern flounders eat a variety of invertebrates, but become
piscivorous when they are about 200 mm long (TL).*77*
COMMENTS ON ADULT FOOD -
In Louisiana, adult southern flounders eat shrimp and fish. In a more
detailed study in Louisiana, Fox and White (1969) reported that striped
mullet (Mugil cephalus) was the major food item of southern flounders,
followed by fat sleepers (Dormitator maculatus) and anchovies (Anchoa).
Larger flounders (150 mm long) ate primarily fish, among which anchovies,
menhaden (Brevoortia sp.), sciaenids, and mullet (Mugil sp.) were most
common.*77*
COMMENTS ON JUVENILE FOOD -
In Texas, Stokes (1977) reported that small flounders (10 to 150mm long) ate
mostly invertebrates (95%) among which mysids were the most common
(32%).*77*
Food Habits - 1 (DRAFT) - Environment Associations
Species flounder, southern
Species Id M010021
Date 27 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
A Water Temperature: Specified in Comments
J Water Temperature: Between 15-21 degrees C
A
J
LIM Dissolved Oxygen: Low [less than 5 mg/l] oxygen concentrations
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 77
REFERENCES FOR FEEDING ADULT ENVIRONMENTAL ASSOC_ - 77
REFERENCES FOR FEEDING JUVENILE ENVIRONMENTAL ASSOC_ - 77
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
Temperature influences the migration of postlarval and adult southern
flounders.*77*
COMMENTS ON FEEDING ADULT ENVIRONTAL ASSOC_ -
In Louisiana coastal waters, adult southern flounders have been collected
at temperatures ranging from 5 to 35 degrees C.*77*
COMMENTS ON FEEDING JUVENILE ENVIRONMENTAL ASSOC_ -
Postlarval migration to estuaries from offshore waters peak when water
temperatures are about 16 degrees (Stokes 1977).*77*
In a laboratory study, postlarval southern flounders attempted avoidance
when dissolved oxygen concentrations fell below 3.7 mg/l. No avoidance
differences were noted at temperatures of 6.1 degrees, 14.4 degrees, or
25.3 degrees C.*77*
Environment Associations - 1 (DRAFT) - Life History
Species flounder, southern
Species Id M010021
Date 27 AUG 96
LIFE HISTORY
Morphology and Identification Aids:
Dorsal fin rays range from 80 to 95; anal rays from 63 to 74, and pecotoral
fin (eye side) rays from 11 to 13. Upper gill rakers on the upper limb of
the first fill arch range from 2 to 3 and lower gill rakers on the lower
limb from 8 to 11. Scales in the lateral line range from 85 to 100. Body
depth is 30% to 47% of standard length (SL). The eyes are on the left side
and color is light to dark brown with diffuse nonocellated dark spots and
blotches. The blindside is white or dusky.*77*
Spawning:
Most southern flounders spawn in late fall and early winter, but some spawn in in
in early spring.
In North Carolina, southern flounders migrate out of estuaries in fall to
spawn. In Texas, they migrate from estuaries into the Gulf of Mexico from
October through December, apparently to spawn. Males move seaward earlier
than females and few remain in the estuaries after November. This
migration is usually preceded by a drop in water temperature of 4 to 5
degrees C. Southern flounders are caught in gulf waters as deep as 63 m.
Females become sexually mature at 2 years of age in Texas. The youngest
mature female southern flounder in northern Florida was 4 years old. Of the
mature females collected in August, 8% of the 4-year-olds, 5% of the
5-year-olds, and 18% of the 6-year-olds were developing eggs.
Southern flounders in Texas were induced to spawn in the laboratory. About
three weeks before spawning took place, males began following gravid females
in the tanks. The first spawning was on December 21. Spawning was at
midday, when females swam to the surface and released eggs that were
immediately fertilized by attending males. Fertilization was 30% to 50%
successful, and 6% to 35% of the eggs hatched in 61 to 76 hr.*77*
Fecundity:
Thirteen southern flounders examined in the laboratory, produced a total of
120,000 eggs (average about 9,230).*77*
Larvae:
In culture, yolk-sac larvae began metamorphosing to postlarvae at 40 to 46
days (8 to 11 mm long): metamorphosis was complete by 50 to 51 days.*77*
Juveniles and Adults:
Postlarvae of southern flounder 18 to 34 mm in total length (TL) were
captured during February, March, and May at Galveston Island, Texas; fish 25
to 51 mm TL were caught in Mississippi River passes during spring.
Southern flounder postlarvae are caught along the Gulf of Mexico coast
during winter and early spring. In Aransas Bay, Texas, the peak movement of
postlarvae flounders into estuaries is in February, when water temperatures
are between 16.0 and 16.2 degrees C. In Texas, Breuer (1962) found
postlarvae 35 to 50 mm TL in December.
Juveniles are generally collected during spring, summer, and early fall.
Juveniles 50 to 100 mm TL were caught on the seaward beaches of islands in
Louisiana in April, and fish 34 to 57 mm long were caught in marsh areas of
the Mobile Delta during December and from February to April. Near the mouth
of the Mississippi River, adults and juveniles were captured during summer
Life History - 1 (DRAFT) - Life History
Species flounder, southern
Species Id M010021
Date 27 AUG 96
in addition to a few adults taken in winter. Near Galveston Island,
Texas, a single juvenile was captured in September. Juveniles and adults
were collected in the Mobile Delta in water of salinities ranging from 0 to
22.2 parts per thousand (ppt).
From April 1974 to February 1975, adult southern flounders migrated in
shallow waters from the Gulf of Mexico to Aransas Bay, Texas; the migrations
were complete by late June. Adult flounders live in Texas bays from June
through November, in water with abundant smooth cordgrass (Spartina
alterniflora).*77*
Growth Characteristics:
The largest southern flounder reported in the literature was 762 mm. The
von Bertalanffy growth model predicts a maximum age of 20 years.
Growth data on the southern flounder are available only from Florida and
Mississippi. Annual growth increments in total length (to the nearest 1 mm)
for southern flounder in Florida, based on scale measurements and analysis
of 177 fish by age group and length (mm), were as follows: 0-I, 79: I-II,
70: II-III, 49; III-IV, 45; IV-V, 46; V-VI, 40; VI-VII, 37; VII-XIII, 34;
and VIII-IX, 41 (Nall 1979). Except for ages VIII-IX, growth rate declined
with an increase in ages.
In Florida the following total length ranges (to the nearest 1 mm) for each
age were reported, I, 79; II, 80-142; III, 84-134; and IV, 170.0-215 (Nall
1979). In Mississippi, southern flounders were larger at the same age
increment than in Florida: II, 230mm; III, 340 mm; and IV, 480mm.*77*
Behavior:
In a Louisiana study of day versus night trawling, 89% of southern
flounders were caught at night, apparently because they are more vulnerable
to trawling at night than during daylight. A tank study confirmed that
flounders are more active at night.
A tag-recapture study of southern flounders in Texas revealed that movements
between and within estuaries rarely exceeded 18 km. The time between
release and recapture ranged from 3 to 212 days.*77*
REFERENCES FOR LIFE HISTORY- 77
Life History - 2 (DRAFT) - Management Practices
Species flounder, southern
Species Id M010021
Date 27 AUG 96
MANAGEMENT PRACTICES
Management Practices - 1 (DRAFT) - References
Species flounder, southern
Species Id M010021
Date 27 AUG 96
References
77* Reagan, R. E., W. M. Wingo. 1985. Species Profiles: Life
Histories and Environmental Requirements of Coastal Fishes and
Invertebrates (Gulf of Mexico) -- Southern Flounder. U.S. Fish
and Wildlife Service Biol. Rep. 82(11.30) pp 9.
References - 1