Habitat Index Analysis of the Harbor Porpoise (Phocoena phocoena) in the Southern Coastal Bay of Fundy, Canada

Abstract

Boat transects were run through a variety of potential habitats of the harbor porpoise (Phocoena phocoena). Depth, topography, current speed, tidal amplitude, surface temperature, and lateness of season were considered in relation to mean sightings of harbor porpoises along each transect. Abundance of porpoises within the study areas was inversely correlated to mean August surface temperatures, possibly because a major prey species (Atlantic herring, Clupea harengus) was associated with vertically mixed waters. Abundance of porpoises was positively correlated both with physiographic features which concentrate herring in near-surface waters, and with increasing depth. The latter correlation may reflect the association of herring with deep water during daylight hours, as well as an aversion of porpoises to shallow, turbulent water. Equations based upon these correlations (adjusted r2 ≥ 0.97 at a scale of 1.0 km2) can be used to estimate the seasonal population density of harbor porpoises in areas of known depth, topography, and surface temperature.