Cape Breton Trough IMMA

Criterion A: Species or Population Vulnerability

While the main qualifying species that occurs in this area, the population of long-finned pilot whales (Globicephala melas) that aggregates here, is not considered vulnerable, it is worth mentioning that four IUCN red-listed species are found regularly in the area. The blue whale (Balaenoptera musculus) is IUCN red-listed as Endangered (EN; Cooke 2018a,b), the North Atlantic right whale (Eubalaena glacialis) is Critically Endangered (CR; Cooke 2020), the fin whale (Balaenoptera physalus) is Vulnerable (VU; Cooke 2018c), and hooded seals (Cystophora cristata) are also Vunerable (VU; Kovacs 2016).

Three of these species are also listed under Schedule 1 of the Canadian Species at Risk Act (SARA – the Canadian legislation for conservation of at-risk species): Atlantic blue whale (Endangered), North Atlantic right whale (Endangered) and Atlantic fin whale (Special Concern).

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

A well-documented aggregation of long-finned pilot whales (Globicephala melas) summers in the Cape Breton Trough and surrounding areas (Kinglsey and Reeves 1998). High site fidelity within this area has been documented for pilot whales. Individuals are known to regularily return to this area, with 61.2% of inidividuals being documented more than once, and 36.2% being documented more than three times despite relatively minimal monitoring coverage from a single whale-watching vessel during the months of July and August (Augusto et al. 2017).  Social structure studies on this population have delineated 21 long-term stable social units, with units being encountered approximately 3-21 days per year from 1998-2011 (Augusto et al. 2017). This regular summer aggregation has also been documented by the Cape Breton Pilot Whale Project through various additional research projects (e.g., McComb-Turbitt et al., 2021; Ottensmeyer and Whitehead, 2003).   There are no other regions along the eastern Canadian coastline currently documented to be occupied consistently by a large aggregation of long-finned pilot whales over the summer and autumn months.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The majority of long-finned pilot whale calves in the Northwestern Atlantic are born during the summer and early autumn (Sergeant, 1962). The Cape Breton Trough area is known to be an important summering ground and calving area for this species, with approximately 85% of encountered groups containing calves (Augusto et al. 2017). Neonate calves are commonly sighted in the July thru September period in this area (Cape Breton Pilot Whale Project, unpublished data). Data collected by Sergeant (1962) from nearby historical inshore summering pilot whales off Newfoundland – a drive hunted population that has not been observed occupying inshore waters since they were exploited in large numbers in the mid 20^th century – showed a defined calving season with a maximum frequency of births occurring mid-August and cessation of calving by the end of October. This is consistent with observations of calves in this IMMA. Given that the gestation period of long-finned pilot whales is approximately a year in duration (Sergeant, 1962; Betty et al. 2023), this also implies that these waters in the Cape Breton Trough where calves are observed are likely an important breeding ground for this species as well.

Sub-criterion C2: Feeding Areas

While the target forage species for many of the marine mammal species that feed in the Cape Breton Trough are unknown, it is an important area for zooplankton and many species of fish driven by strong phytoplankton productivity in the northern portion of the Cape Breton Trough (DFO 2007; Lavoie et al. 2007). Additionally, the Cape Breton Trough is along a known migration route for baitfish species such as the alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), American shad (Alosa sapidissima), Atlantic saury (Scomberesox saurus), and Atlantic mackerel (Scomber scombrus) (Dufour and Ouellet 2007).

It is thought that the large numbers of long-finned pilot whales that come inshore within the Cape Breton Trough area in the summer are following shortfin squid (Illex illecebrosus) (Abend and Smith 1999), though they likely also forage on other species of fish, such as mackerel and herring when available. Pilot whale feeding and foraging hotspots have been well documented within this area (McComb -Turbitt et al. 2021), providing evidence of the importance of the Cape Breton Trough as a foraging area for this species.

It is also worth noting that there is a documented aggregation of minke whales (Balaenoptera acutorostrata) that use this area during the summer for feeding (Coomber et al. 2021 ; Cape Breton Pilot Whale Project, unpublished data). Some individual minke whales have been observed returning to the same feeding area annually over the past decade (Cape Breton Pilot Whale Project, unpublished data). Other species such as fin whales, Atlantic white-sided dolphins (Lagenorhynchus acutus) , harbour porpoises (Phocoena phocoena), and humpback whales (Megaptera novaeangliae) forage in this area during the ice-free months (Lesage et al. 2007; Coomber et al. 2021), while grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina vitulina) are more generalist predators that forage in the area throughout the year (Coomber et al. 2021; Vacquie-Garcia et al 2024). While these other species are known to feed in the area, there is less evidence available to demonstarte that the Cape Breton Trough is a particularly important foraging area for these other species.

Criterion D: Special Attributes

Sub-criterion D2 – Diversity

There is a large diversity of marine mammal species observed to regularly use the Cape Breton Trough area (Coomber et al. 2021; Cape Breton Pilot Whale Project, unpublished data), thought to mainly be driven by strong phytoplankton productivity found in northern areas of the Cape Breton Trough (DFO 2007; Lavoie et al. 2007). Some species use the trough all year, like grey and harbour seals (Coomber et al. 2021; Vacquie-Garcia et al 2024). Others marine mammals occur here seasonally during the ice-free months (approximately May to December), such as pilot, minke, fin, and humpback whales, as well as white-sided dolphins and harbour porpoises (Coomber et al. 2021; Lesage et al. 2007; Cape Breton Pilot Whale Project, unpublished data). There are also additional cetacean species more occasionally reported in the area such as blue and right whales, as well as white-beaked (Lagenorhynchus albirostris) and common dolphins (Delphinus delphis) (Coomber et al. 2021; Lesage et al. 2007; Cape Breton Pilot Whale Project, unpublished data). Other pinnipeds, such as hooded and harp seals (Pagophilus groenlandicus), come to this area during the middle of winter when pack ice forms to give birth to their pups on the ice (Coomber et al. 2021; Lesage et al. 2007). It is clear from available data that the Cape Breton Trough is important to marine mammals throughout the year, with strong seasonal significance for a number of species.

The Cape Breton Pilot whale Project, led by the Whitehead Lab at Dalhousie University, has been conducting cetacean research surveys from whale-watching vessels in this area annually since its establishment in 1998.   Though these surveys have been mainly focused on long-finned pilot whales, any other cetacean species observed are also documented. Sightings from these efforts over the past two and a half decades demonstrate regular occurrence of long-finned pilot, minke, fin, humpback, right, and blue whales, Atlantic white-sided, common, and white-beaked dolphins, as well as harbour porpoises in the Cape Breton Trough (Cape Breton Pilot Whale Project, unpublished data).