Sperm whales (Physeter macrocephalus) and beaked whales (Mesoplodon spp. and Ziphius cavirostris) are deep‐diving cetaceans that frequent shelf‐edge and Gulf Stream waters off the northeast U. S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995–1998) shipboard surveys were analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates were lower for beaked whales, both taxa occupied similar habitats. Beaked whales were concentrated at the colder shelf edge, whereas sperm whales were associated with warmer off‐shelf water. Mean sighting rates for both taxa were higher in canyon features, but only beaked whale sighting rates were significantly different between canyon and non‐canyon habitat (Wilcoxon signed rank test P= 0.007). Within the shared habitat, the two taxa were separated at fine‐scale based on oceanographic features.
Aerial counts of harbor seals (Pboca vitulina concolor) on ledges along the Maine coast were conducted during the pupping season in 1981, 1986, 1993, 1997, and 2001. Between 1981 and 2001, the uncorrected counts of seals increased from 10,543 to 38,014, an annual rate of 6.6 percent. In 2001 30 harbor seals were captured and radio‐tagged prior to aerial counts. Of these, 19 harbor seals (six adult males, two adult females, seven juvenile males, and four juvenile females) were available during the survey to develop a correction factor for the fraction of seals not observed. The corrected 2001 abundance estimate was 99,340 harbor seals. Productivity in this population has increased since 1981 from 6.4% pups to 24.4% pups. The number of gray seals (Halichoerus grypus) counted during the harbor seal surveys increased from zero in both 1981 and 1986 to 1,731 animals in 2001.
The stock structure of the sei whale Balaenoptera borealis in the North Atlantic is unknown, despite years of commercial hunting. New and up-to-date data on distribution and movements are essential for the creation of plausible hypotheses about the stock structure of this species. Between 2008 and 2009 satellite tracks of 8 sei whales were obtained, 7 during spring and 1 in late September. Using a hierarchical switching state-space model we investigated the movements, behaviour and the role of distinct areas in their life history. Two distinct phases corresponding to migratory and foraging movements were identified. A migratory corridor between the Azores and the Labrador Sea is clearly identifiable from the data. Behaviour consistent with foraging was observed frequently in the Labrador Sea, showing that it constitutes an important feeding ground. A link between the Labrador Sea and other feeding grounds to the east is deemed likely. The data also support a discrete feeding ground in the Gulf of Maine and off Nova Scotia. A possible link between the feeding grounds in the Labrador Sea and wintering grounds off northwestern Africa is proposed.
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