Blue Whale

(Balaenoptera musculus)

 

Family: Balaenopteridae

Species: Balaenoptera musculus

Length: 20 to 25 meters. The biggest specimen was 33,58m, captured in South Georgia.

Weight: 75 to 130 metric tons.

Life expectancy: estimated around 70-90 years, with an inferred generation time of 31 years.

Diet: Primarily Krill (euphausiids) and copepods. The St Lawrence blue whales are known to feed predominantly on Krill species Meganyctiphanes norvegica and Thysanoessa raschii.

Behaviour: Found mainly as solitary individuals or in pairs, and occasionally in small groups. They do, however, aggregate in larger groups in areas of dense prey patches.

 

Blue whale fluke

Fluke (tail) of a blue whale (Balaenoptera musculus)

 

The Blue Whale (Balaenoptera musculus) is the largest known animal ever to inhabit our planet, and surpasses even the largest dinosaurs in size. The Blue whale is what is commonly referred to as a 'cosmopolitan species', meaning that they can be found across most oceans. In Quebec, they can be seen in the estuary of the Saint-Lawrence river and along the Gaspesian peninsula in the summer and fall. They used to commonly occur in the Gulf of St Lawrence in the Mingan-Anticosti area, but are much less frequently observed there now as we have seen a decrease in sightings over the last 10 years. Some individuals are sporadically seen in the St. Lawrence in winter.

Blue whales used to be abundant around the world, but their population was severely depleted following the nineteenth and early twentieth-century commercial whale hunt, when at least 13,000 specimens were caught in the North Atlantic. The species is very slowly recovering at a global level, however they remain well below pre-whaling numbers and have been classified as 'Endangered' according to the IUCN (International Union for Conservation of Nature). The North Atlantic population is divided into two geographical subpopulations: Northwest Atlantic (NWA) and Northeast Atlantic (NEA). The Northwest Atlantic population has been added to the list of the Species At Risk Act (SARA) in Canada. MICS' research results indicate that there is very low population recruitment, meaning that the birth rate (measured by calf sightings) has remained quite low. In almost 40 years of blue whale research, only 23 calves have been identified in the NWA.

MICS was the first organization to carry out long-term studies of the endangered blue whale. We have since studied blue whales throughout the St. Lawrence, in the Sea of Cortez, off Iceland, West Greenland and the Azores. We have compiled extensive blue whale photo-identification catalogues for the Northwest and Northeast Atlantic as well as the Sea of Cortez. MICS is the curator of the North Atlantic catalogues, which means that any blue whale photos taken in this region by other researchers, sailors, and whale-watchers are sent to us for matching. The Northwest Atlantic catalogue now contains around 500 individual whales, while 560 have been cataloged for the Northeast Atlantic. New whales are added to the catalogue almost every year. In 2017, 41 blue whales were identified, which is a bit below average considering it can range between 30-100. Blue whales are identified thanks to their mottled grey pigmentation pattern. Richard Sears was the first to use this feature as a method for identifying and recognizing individual blue whales as a research tool.

However, estimating the population size throughout the North Atlantic has proven most difficult due to the constraints of following and surveying such a transient species across ocean basins. Based on mark-recapture models, the Northwest blue whale population has been estimated at around 150-200 individuals in the St Lawrence Estuary, where sighting data has been most consistent. Their migratory movements are not yet very well understood, but some NWA blue whales travel North as far as Davis Strait and the western shore of Greenland, or South through the Cabot Straight along the US east coast as far south as the Carolinas. They also disperse seasonally throughout eastern Canadian shelf waters and the St. Lawrence. Thus far there appears to be only limited exchange between NWA and NEA subpopulations, because we have only discovered one blue whale that was matched to both NWA and NEA catalogues.

Blue whales can be found in the St. Lawrence from April to January; however, they are seen regularly in the Estuary and along the Gaspésie Peninsula from August to December. Concentrations can be found in the Mingan/Anticosti region, off Sept-Îles, and from Pointe-des-Monts to Grandes Bergeronnes. Since 2010, MICS has been involved in a satellite tagging project, which aims to discover more on blue whale regional dispersal and migration.

 

Blue whale

 Photo-ID of Phoenix - RSD (Right Side Dorsal)