Observations on the fish fauna associated with offshore platforms in the northeastern Gulf of Mexico

Abstract

The fish fauna associated with two U.S. Navy research platforms, Stage I and Stage II, in the
northeastern Gulf of Mexico off Panama City, Fla., was studied at irregular intervals from 1970 to
1974. Such platforms function as artificial reef habitats and support diverse and abundant fish
populations not normally characteristic of the open sandy bottoms in the area.
A total of 101 taxa (identified to family or species) was recorded at the two platforms; 61 species
were observed at Stage I in water 32 m deep and 86 taxa at Stage II in water 18 m deep. The greater
number of species recorded at the shallower location may be more a result of the greater number of
observations made there than of differences in the two habitats. The number of species present at the
platforms varies considerably at different times of the day and year. Species numbers are greatest
during the summer and fall, but many species begin to move offshore or southward as the water
temperature drops, and only about 50-60% of those recorded at the platform remain in December. The
number of species diminishes to about 16% in February at Stage II, then increases gradually with the
rising water temperature in the spring.
Major species occupying the platform habitats include fishes usually characteristic of pelagic,
inshore (coastal or estuarine), and rocky reef environments. At the platforms, the pelagic species and
most of the larger predators occupy various levels of the water column, either directly below or
surrounding the structure, while most of the other species are associa ted either with the pilings and
cross-members of the platform or with the bottom. For some of the species, the platform provides food
and shelter, while for others, it offers only shelter. Some species may be present only to feed on the
numerous fishes and other organisms concentrated there. Diel rhythms of activity are obvious for
many of the fishes, with some species active only during the day, and others only at night.