Research Document - 2009/098
Information relevant to the documentation of habitat use by St. Lawrence beluga (Delphinapterus leucas), and quantification of habitat quality
By A. Mosnier, V. Lesage, J-F. Gosselin, S. Lemieux Lefebvre, M.O. Hammill, and
T. Doniol-Valcroze
Abstract
The current population size and distribution range of St. Lawrence beluga are a fraction of those used historically. Their core distribution is centered on the Saguenay River, and is now located between the Battures-aux-Loups-Marins and Rivière-Portneuf / Rimouski in the Estuary, and Baie Ste-Marguerite in the Saguenay River. Concentration areas outside of this sector vary seasonally, as they did in the 1930s, but are now constrained within a zone located between Battures-aux-Loups-Marins and Sept-Îles / Cloridorme (vs west of Quebec City to Natashquan in the 1930s), with only rare observations in the Baie des Chaleurs. St. Lawrence beluga distribution range is small compared to other beluga populations, and even smaller during summer.
The timing and extent of seasonal movements of beluga are likely dictated by at least three key drivers: sea ice, predation risks, and food availability. However, little is known about beluga distribution outside of summer. Currently available knowledge indicates that sex- and age-sêcific spatial segregation is typical of the species during summer. The Upper Estuary, where females accompanied by calves and juveniles concentrate, is likely an important habitat for calving and juvenile rearing. Reasons for sexual segregation and habitat characteristics that are critical to the survival of females, juveniles and calves in this sector are unclear. The species also consistently aggregates at certain river mouths during summer, which suggest that they are an essential part of beluga habitat. The functions of these areas are unknown. Several smaller areas where beluga occur on a regular basis or where they spend relatively large proportions of their time exist within their seasonal distribution area, some of which have been identified for the summer period. However the current understanding of the functions and key features of these habitats and of habitat use and movements among these areas by beluga does not allow the assessment of their relative importance for the survival of the population. Given that current distribution is small relative to that used historically, a degradation of key habitat features or a reduction in key habitat availability would probably result in negative effects on recovery. In this context, preserving access to and integrity of areas used currently or historically by a large proportion of the population is considered important for the recovery and future range expansion of the population. Species characteristics such as longevity, social organization and learned behaviours may influence seasonal habitat use, and might delay re-colonization of areas used historically.
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