Characterization of beaked whale (Ziphiidae) and sperm whale (Physeter macrocephalus) summer habitat in shelf-edge and deeper waters off the northeast US

Sperm whales (Physeter macrocephalus) and beaked whales (Mesoplodon spp. an d Ziphius cavirostris) are deep-diving cetaceans that frequent shelf-edge a nd Gulf Stream waters off the northeast U.S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995-1998) shipboard surveys we re analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates we re lower for beaked whales, both taxa occupied similar habitats. Beaked wha les were concentrated at the colder shelf edge, whereas sperm whales were a ssociated with warmer off-shelf water. Mean sighting rates for both taxa we re higher in canyon features, but only beaked whale sighting rates were sig nificantly different between canyon and non-canyon habitat (Wilcoxon signed rank test P = 0.007). Within the shared habitat, the two taxa were separat ed at fine-scale based on oceanographic features.