Surveys were conducted in the northern Gulf of Mexico during the spring sea
sons of 1992, 1993, and 1994 to determine the distribution, abundance, and
habitat preferences of oceanic cetaceans. The distributions of bottlenose d
olphins (Tsursiops truncatus), Risso's dolphins (Grampus griseus) Kogia spp
. (pygmy [kogia breviceps] and dwarf sperm whales [Kogia sima]) pantropical
spotted dolphins (Stenella attenuata), and sperm whales (Physeter macrocep
halus) were examined with respect to depth. depth gradient, surface tempera
ture, surface temperature variability the depth of the 15 degreesC isotherm
, surface chlorophyll concentration, and epipelagic zooplankton biomass. Bo
ttlenose dolphins were encountered in two distinct legions: the shallow con
tinental shelf (0-150 mi and just seaward of the shelf break (200-760 mi. W
ithin both of these depth strata, bottlenose dolphins were sighted more fre
quently than expected in regions of high surface temperature variability wh
ich suggests an association with ocean fronts. Risso's dolphins were encoun
tered over the steeper sections of the upper continental slope (200-1000 m)
, whereas the Kogia spp. were sighted more frequently in waters of the uppe
r continental slope that had high zooplankton biomass. The pantropical spot
ted dolphin and sperm whales were similarly distributed over the lower cont
inental slope and deep Gulf (>1000 m), but sperm whales were generally abse
nt from anticyclonic oceanographic features (e.g. the Loop Current. warm-co
re eddies) characterized by deep occurrences of the 15 degreesC isotherm. H
abitat partitioning, high-use areas, species accounts, environmental sampli
ng limitations, and directions for future habitat work in the Gulf of Mexic
o are discussed.