Adults are found from 60 to 250 feet deep and occasionally
to over 500 feet. Gag tend to orient themselves
around some sort of bottom relief, rocks, reefs, shipwrecks,
or offshore oil and gas platforms. Size is related to
water depth, with average size increasing as the water
becomes deeper. Young fish can be found in nearshore waters
and even bays and other estuarine waters.
are most identifiable by their lack of distinguishing features.
Their body color is an overall mottled gray. The darker body
marking may be arranged in "kiss-shaped" patterns,
resembling the box-shaped patterns on the true black grouper.
They lack the streamer-points on the tail fin that scamp and
yellowmouth grouper have and lack the yellow color in and
near their mouths. They most closely resemble the black grouper,
but are lighter in color, especially on the fins.
Gag are a fairly well researched grouper. They spawn from
December to May, with peaks on the full moons between February
and early April. After hatching, the tiny baby grouper are
carried into nearshore and inshore waters by currents. Many
young gag spend their first summer on oyster reefs feeding
on small shrimp and other creatures. After 4 months, the survivors
have grown to 5 inches and switched to a fish diet, which
preferred food for the rest of their lives.
With the cooler temperatures of fall, the small gag move to
channels for migration offshore. By October, they are 12 inches
long and all are females. After moving offshore, gag grouper
stake out a territory that they seldom leave until old enough
to spawn. Gag grouper grow rapidly until they are 10 years
old and an average size of over 40 inches. After that, growth
rates are very slow. Either alone or in small groups, gag
will travel to specific areas to form spawning groups. After
spawning, the largest fish
will turn into males. Gag under 32 inches and 5 years old
females. By 42 inches and 11 years of age, the sex ratio is
about even. Larger fish are mostly males. Female fish outnumber
In recent years, this imbalance in sex ratios has become more
pronounced, causing some fisheries managers to become concerned.
The larger male fish are aggressive feeders and once located,
they are easy to catch. The increased efficiency of fishermen
is allowing them to target specific gag habitat.