We describe an integrative approach to studying the fine-scale distribution of harbour porpoises Phocoena phocoena in the Bay of Fundy, using satellite telemetry, line transect surveys and remote sensing techniques. Analysis of satellite telemetry data from 6 porpoises (5 male, 1 female) revealed that over the course of a month individuals ranged across large areas (7738 to 11 289 km 2 ) but concentrated their movements in small focal regions (August mean = 294 km 2 , September mean = 252 km 2 ), often proximate to islands, headlands, or restricted channels. Line transect surveys (n = 25 flood tide, n = 20 ebb tide) in the focal region of 2 tagged animals revealed that relative porpoise density (animals km -2 ) was significantly greater during flood (9.59) than ebb tide phases (1.79). Hydro-acoustic prey surveys revealed aggregations of prey along localized fronts in this region. Remote sensing images indicated the presence of an island wake in the focal region during flood tides, providing an ecological context for our observations of high densities of porpoises. Remote sensing revealed the existence of a headland wake in the focal region of another porpoise near Campobello Island. These results support the hypothesis that regions of enhanced relative vorticity, like island and headland wakes, aggregate prey and represent important foraging habitat for harbour porpoises in the Bay of Fundy.KEY WORDS: Harbour porpoise · Foraging · Fine-scale oceanography · Island wake · Satellite telemetry · Line transects · Remote sensing Resale or republication not permitted without written consent of the publisher

No abstract

Marine predators forage in tidally induced oceanographic features, where they exploit predictable aggregations of prey. Very little, however, is known about how the physical forcing within these features affects their behaviour at a fine scale. During the summers of 2000 and 2002, we combined a series of cliff-top observations and boat-based surveys to describe the movements of fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata within a predictable island wake occurring near Grand Manan Island in the Bay of Fundy, Canada. We recorded the location of fin and minke whales as they surfaced in or near the wake. We also examined the movements of individual fin whales using focal follow techniques to assess their habitat use within 3 distinct oceanographic regions (non-wake habitat, eddy habitat and free stream habitat) of the study area. Fin and minke whale occurrence was highest during flood tides and lowest during the mid-ebb phases. Fin (33) and minke whale (64) sightings were concentrated in areas characterised by slower current velocities -the region influenced by the eddy system formed within the wake. Nine individual fin whales, identified through photographs, spent a disproportionate amount of time within the eddy habitat portion of the study area, with occasional forays into free stream habitat. Foraging in the high-vorticity regions of the wake likely allows whales to exploit higher prey concentrations than in the free stream habitat or non-wake habitat.

No abstract

We collected data on the distribution of fin whales (Balaenoptera physalus) and minke whales (Balaenoptera acutorostrata) in the Bay of Fundy, Canada from a whale-watching vessel during commercial tours between July and September 2002. A single observer recorded the positions, species, numbers and surface activity of whales encountered during boat tours. We controlled for biased search effort by calculating sightings rates for both species in cells measuring 2' latitude by 2' longitude throughout the study area. Sightings rates were calculated by dividing the number of sightings of fin and minke whales in each cell by the number of visits by the tour boat to that cell. We used generalized additive models and generalized linear models to examine the influence of benthic topography on whale distribution patterns. Models showed a non-linear relationship for minke whale sighting rates with increasing benthic slopes and a linear relationship for minke and fin whale sightings rates with increasing water depth. Sightings of minkes were concentrated in areas subject to tidal wakes near the northern tips of Grand Manan and Campobello Island. Fin whales were also found off the northern tip of Grand Manan but sighting rates for this species were highest in areas with less benthic sloping topography adjacent to the relatively deep Owen Basin. Foraging was recorded during 87% of all whale encounters and our results indicate that whale distribution in this area is likely to be influenced by depth, bottom topography and fine scale oceanographic features that facilitate foraging.