Bryde's whales Balaenoptera edeni are the only resident baleen whale species in the Gulf of Mexico (GoM), where they are extremely rare, have a restricted distribution, and represent a unique evolutionary lineage. The reasons for the restricted distribution and small population size are unknown, but high levels of industrial activity in the GoM may be a major factor. We evaluated the geospatial overlap of GoM Bryde's whales with 2 industries known to impact baleen whale species: commercial shipping and commercial fisheries. We further evaluated the potential for impacts by examining the first dive behavior data collected from a kinematic tag attached to a GoM Bryde's whale for 3 d. Vessel traffic and fishery effort are low in GoM Bryde's whale habitat compared to the rest of the northern GoM, but several shipping lanes transit through the habitat, and the reef fish bottom longline fishery exerts considerable effort within the habitat. The tagged whale exhibited diel diving behavior with diurnal deep dives and foraging lunges at or near the sea floor, and shallow nocturnal diving, with 88% of its nighttime spent near the surface within the draught depths of most large commercial vessels. Given the location of commercial shipping traffic in GoM Bryde's whale habitat, ship strikes may pose a threat to this population if the whales commonly spend time near the surface, especially at night. Also, if bottom or near-bottom feeding is a normal feeding strategy for these whales, there is potential for entanglement in bottom longline gear. Managing these threats may improve population recovery.

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Guiana dolphin (Sotalia guianensis) encounters were documented in Sepetiba Bay. For the purpose of this study all dolphin sightings were classified as groups or aggregations. Groups (N ¼ 268, x ¼ 20, range ¼ 1-90) consisted of dolphins in apparent association usually engaged in the same behaviour and moving in the same direction. Aggregations (N ¼ 108, x ¼ 204, range ¼ 100 -450) consisted of temporal association of numerous groups gathered in an area, totalling several hundred individuals usually engaged in the same behaviour but not necessarily moving in the same direction. Guiana dolphin groups and aggregations differed significantly in behavioural activity, spatial and temporal distribution and age composition. Most aggregated dolphins were engaged in foraging/feeding activities and primarily located at the interior of the bay, and also, aggregations were more likely recorded during morning hours and had more neonates and calves present when compared to groups. The plotted GPS records of aggregations formed two distinct clusters of distribution within the bay, indicating potential areas where conservation strategies could be implemented.

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