Although
18 species of the lefteye flounder family are found in the
northern Gulf of Mexico, flounder in Louisiana almost invariably
means the southern flounder. Its Latin name, Paralichthys
lethosigma, literally means “parallel fish that
forgot its spots.”
In Louisiana, southern flounders can be found from 100 miles
up the Mississippi River in pure fresh water, out to full-strength
seawater off the coast, although most studies show that they
are most common at moderate salinities.
Most research indicates that male flounders stay in offshore
waters year-round. Male flounders are small, seldom growing
larger than 10 to 12 inches, but the females grow larger and
move longer distances. Females may reach 23 inches long, and
spend most of the year in inshore waters, only migrating offshore
during October to December to spawn. Excellent catches of
flounder can be made during this period.
Female southern flounders spawn several times during their
short annual spawning period, producing about 100,000 eggs
each spawn. Spawning seems to be triggered by water temperatures
of about 56 degrees F and usually occurs between 5 and 9 a.m.
After hatching, larval southern flounders grow most rapidly
in highly saline waters. Young flounders begin to appear in
Louisiana inshore estuaries between January and April, and
range 1/4 inch to 2 inches in length. Like other fish, flounders
hatch with one eye on each side of the head. Movement of the
right eye to the left side of the head begins when the fish
is 1/3 to 1/2 inch long and is complete when the fish is 3/4
inch to 1 inch long. At this same time, the left side develops
its dark color and the right side turns white.
After hatching, southern flounder larvae eat microscopic floating
animals (plankton). As juvenile fish, they eat small bottom
animals. At about 6 inches long, they adopt their adult diet
of fish and shrimp. One study in Lake Pontchartrain showed
that 89 percent of their diet was fish, with 41 percent being
anchovies (sardines). In Barataria Bay, another study showed
that 94 percent of their diet consisted of mullets and anchovies.
In Texas,
researchers have noted that the southern flounder is the dominant
predator of shrimp in the spring, and that most of its diet
is anchovies, mullets, shrimp, menhaden (pogies) and croakers.
In Mississippi, southern flounders’ stomachs most frequently
contained fish, with one-third having shrimp in them. Interestingly,
as flounders get larger they don’t eat larger fish,
they just eat more small ones.
Female
southern flounders grow more rapidly than males. A research
project in Louisiana did not find a male southern flounder
over 13.5 inches long. Another study in Georgia showed no
males more than 16 inches long, and research in Texas showed
no males over 12.8 inches long. Female flounders grow quickly
their first two years; then their growth slows. Approximate
average lengths at each age for females are: Age 1, 10 inches;
Age 2, 16.7 inches; Age 3, 18.8 inches; Age 4, 19.6 inches;
Age 5, 20 inches; Age 6, 20.4 inches; and Age 7, 20.5 inches.
Few females live beyond seven years old and almost no males
live past three years old.
Flounders
are considered “ambush predators.” Instead of
actively pursuing their prey, they lie in wait in areas that
are likely to concentrate or disorient small fish or shrimp.
From their position on the bottom, flounders pounce on these
animals as they move by.
Because
of their feeding habits, large numbers of flounders will concentrate
in good ambush areas. Especially productive are current-swept
points and channels that serve as choke points for tidal currents.
Southern
flounders take live bait, jigs, or even spoons that are fished
near the bottom. Because their mouth opens side-to-side, rather
than vertically, small hooks will produce more hook-ups than
large hooks.
Flounders
may also be gigged with a one-pronged spear in shallow waters
at night by fishermen using lanterns for illumination. Firm
sandy bottoms are preferred for easy wading. Gigging is most
successfully conducted on a rising tide and in clear water.
The largest flounders are almost invariably gigged in October
and November near Louisiana’s barrier islands, as the
larger females appear in these waters during their spawning
migration to offshore waters.
Currently,
the daily recreational limit on southern flounders is 10 per
day. The possession limit (on land) is 10 southern flounders
per day per licensed person for each consecutive day spent
on the water. There is no minimum size limit on southern flounders
in Louisiana.
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