Habitat important des baleines à bec communes, population du plateau néo-écossais

Abstract

The Endangered Scotian Shelf population of northern bottlenose whales (NBW) consists of fewer than 170 individuals. The Gully, Shortland, and Haldimand canyons have been designated as Critical Habitat for the population while the inter-canyon areas have been identified as important habitat. Multiple sources of data were considered, including sightings, satellite telemetry data, and detections of NBW foraging clicks from towed hydrophone array surveys and bottom-moored passive acoustic monitoring (PAM) systems. Detected foraging clicks were used to estimate temporal persistence of relative habitat use and develop robust ensemble species distribution models (SDMs) using environmental predictors to help assess additional important habitat for the population. Some reservations were expressed by committee members regarding the model results that may influence the quantitative description of habitat suitability within the proposed boundaries of important habitat; however, the important habitat boundaries are also supported by the other sources of data. Continental slope waters (400-3,200 m bottom depth) extending from the Canada-US border to southern Labrador were identified as important habitat with year-round presence of NBW. Deeper waters and areas farther north were not assessed. The functions supported by this identified important habitat include foraging, feeding, and movement. Acoustic detections of foraging clicks indicate that foraging occurs throughout the identified important habitat, with most persistent foraging occurring in the Gully and areas northeastward. The habitat identified among areas of higher persistent foraging is important for movement across the entire important habitat area. Other potential habitat functions, such as socialization, resting, and reproduction, could not be evaluated with the available data. The biophysical features supporting foraging, feeding, and movement are the continental slope marine environment, water quality, acoustic environment, physical space including the entire water column, and food supply. There may be additional features that have not yet been defined or evaluated. Quantitative attributes were defined for the continental slope marine environment as areas within a 400-3,200 m bottom depth range. Data were insufficient to define quantitative attributes for the other biophysical features listed above. Activities likely to destroy this habitat are associated with the published threats of climate change, acoustic disturbance, fisheries interactions, vessel presence (associated with the threat “vessel strike” but more relevant for assessing impacts on habitat), and pollution and chemical contaminants. It is unknown if the important habitat identified here is sufficient to achieve the recovery objectives for the population and additional important habitats may remain to be identified. A revised Schedule of Studies should focus on continued data collection in continental slope waters to increase understanding of habitat functions, features, and attributes within this area, as well as data collection in deeper waters to determine if additional important habitat exists beyond continental slope waters.