| Summary: | Relatively little is known of community ecology associated with cetacean distributions. A multi-species approach was used to investigate physical and biological environments associated with several cetacean species in the northwest Atlantic. Cetacean distributions were analyzed for relationships to physical oceanographic variables and to densities and species composition of zooplankton. Both physical and biological variables helped explain variation in cetacean distributions. Although zooplankton are not prey items for the species examined here, results showed the zooplankton community can be used to describe differences in habitat preference between cetacean species. Zooplankton community composition was not separable from physical factors, but did contribute explanatory power not provided by analyses of cetacean distributions in terms of the physical environment alone. The importance of physical or biological data in describing cetacean distributions varied between cetacean species, and apparent similarities in habitat use were found for some species. Variance in sperm whale (Physeter catodon) distributions were not well explained by the zooplankton community, but a clear relationship of sperm whales with thermal habitat was found in the vicinity of a warm-core ring. The thermal habitat most used by sperm whales was found to have a zooplankton community differing from the other regions where sperm whale densities were low. Greater than half the variance in Atlantic white-sided dolphin (Lagenorhyncus acutus) distributions was explained by the zooplankton community. Physical and biological data described niche separation between minke whales (Balaenoptera acutorostrata), beaked whales (Mesoplodon spp.), white-sided dolphins and pilot whales (Globicephala spp.), but demonstrated niche similarity for sperm whales, striped dolphins (Stenella coeruleoalba) and common dolphins (Delphinus delphis). Zooplankton communities and densities were used to suggest that a hypothesized preference of cetaceans for submerged canyon regions is more a function of bathymetric structure than of secondary production. Niche similarities and differences between cetacean species aid in generating hypotheses concerning degree of interaction within the cetacean community, and permit studies of density dependent habitat selection taking trophic relationships into consideration.
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