Research Document 2018/007

Occurrence of Blue Whales (Balaenoptera musculus) off Nova Scotia, Newfoundland, and Labrador

By Moors-Murphy, H.B., Lawson, J.W., Rubin, B., Marotte, E., Renaud, G., and Fuentes-Yaco, C

Abstract

This study presents a summary of multiple sources of information to assess the spatial and seasonal distribution of Blue Whales in areas off eastern Canada outside the Gulf of St. Lawrence. Aerial and vessel-based systematic surveys, opportunistic sightings, acoustic monitoring, and species distribution modelling (SDM) identified five potentially important areas for Blue Whales off Nova Scotia, Newfoundland and Labrador: (1) deep water areas along the continental slope of the Scotian Shelf, (2) deep water areas along the continental slope of the Grand Banks south of Newfoundland, (3) deep water areas of the Laurentian Channel, (4) shallower water areas off the southwest coast of Newfoundland, and (5) shallower areas on the western Scotian Shelf. While Blue Whales were detected visually and/or acoustically in these areas, and their importance is further highlighted by the SDM results, there has been little Blue Whale focused research in these areas and therefore exactly how, and why, Blue Whales use these areas remains unknown. There is some suggestion in the acoustic data of a difference in use of these areas in summer (when the majority of arch calls are detected, which are made by both sexes and are thought to be related to foraging) and winter (when male-specific songs thought to be related to reproductive activities are detected). Sightings and acoustic detections indicate that Blue Whales occur year-round outside the Gulf of St. Lawrence with some seasonal peaks in call presence observed in July-August and December-January that appear to correspond to inward/outward movements of Blue Whales through the Cabot Strait. Photo-identification studies suggest that some individuals that occur off Nova Scotia and Newfoundland also occur in the Gulf of St. Lawrence, but also that some Blue Whales appear to remain outside the Gulf. Future research can be informed by the results of this and other recent studies. Suitable habitat for Blue Whales predicted by the SDM represent priority areas where monitoring efforts for Blue Whales (including passive acoustic monitoring and aerial and/or vessel-based surveys) should be focused in the future. Future monitoring efforts should also include expanded monitoring of Blue Whales and their prey in offshore areas where little survey effort has occurred. Additional photo identification effort outside the Gulf of St. Lawrence is warranted as a means to collect information on Blue Whale movements and activities, especially in deeper offshore waters. The potential impact of ice entrapment mortality should also be better studied given the number of mortalities that have occurred in the past few decades.

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