If ever
a motto could be used to describe a fish, this one describes
the dolphin (Coryphaena hippurus). This brilliantly-colored
open-ocean fish is found worldwide wherever waters are above
68ºF. In the Gulf of Mexico, dolphin support a substantial
fishery, primarily in the summer months.
Dolphin
have an explosively fast growth rate. It may be the only fish
for which scientists can measure their growth rate per day.
In the Gulf of Mexico, dolphin grow at the rate of five inches
per month, toping out at a maximum size of four and one-half
to five feet in length in two years. Then they die! Scientists
estimate that 100 percent of Gulf of Mexico dolphin die before
they are two years old. Live fast-die young!
Dolphin
begin spawning when they are almost 21 inches long during
their first year of life. In the Gulf, spawning occurs in
the summer in high-salinity offshore waters at water temperatures
of 75ºF or higher. Particularly high numbers of larval
(baby) dolphins have been found near the Mississippi River
delta. They spawn repeatedly during the season, laying 85,000
to 1.5 million eggs per spawn, with larger fish producing
more eggs.
Dolphin
are eating machines. In the Gulf of Mexico and south Atlantic,
they eat more triggerfish than anything else, followed by
decapods (shrimp relatives), squid, jacks and flying fish.
Dolphin
are pursued by both recreational and commercial fishermen,
with recreational landings being six times higher than commercial
landings in the Gulf of Mexico. More females than males are
caught in the fishery. It seems that small fish of both sexes,
and females of all sizes, spend more time around floating
objects and seaweed rips, and are therefore easier to locate.
Large males spend more time in open water traveling between
female dominated schools near floating cover. This makes females
(and small dolphins) easier for fishermen to find and therefore
catch. Females resemble males in color, but have a more rounded
forehead profile compared to the blunt vertical profile of
male fish. The biology of this fish — short life span,
fast growth rate, and early maturity — suggests that
dolphin are a fish that is not easily overfished.
The dolphin
may be difficult to separate from its smaller relative, the
pompano dolphin, (Coryphaena equisetis). The only
sure way is to inspect the shape of the tooth patch on the
tongue. In dolphin it is round; in pompano dolphin it is noticeably
squarish in shape. Pompano dolphin are often found offshore
mixed with dolphin. It is likely that a high percentage of
the small dolphin caught in the Gulf of Mexico are pompano
dolphin. The maximum size of pompano dolphin is about five
pounds, but they usually average much smaller.
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