Boomerang

Distinctive Traits

Boomerang, also known by the identification number Bp060, has been observed in the Saguenay-St. Lawrence Marine Park area since September. This female is recognizable by the shape of the rear part of her boomerang-shaped dorsal fin. A semicircular notch is located at the base of her dorsal fin and since 2011, an additional, albeit inconspicuous notch located at the tip of this fin makes identifying her that much easier. Boomerang has been a regular summer visitor to the Estuary for over 20 years. To identify her via photo pairing – i.e. comparing pictures taken on the water with those in the catalogue – researchers focus their attention on her right chevron, and more precisely on the set of lines and patterns on the back of her head.

Her Story

Just like other fin whales, such as: Captain Hook, Newkie Brown, or U2, Boomerang belongs to the North Atlantic population of fin whales. These rorquals are known to migrate between their feeding and wintering grounds each year. Though we know they visit the estuary in the summertime and go to the warmer Atlantic waters in the wintertime, we do not know where exactly they go when they are not in the North Atlantic. Boomerang comes to the cold and nutrient-rich waters each summer to feed on krill or small schooling fish, such as: herring and capelin. She sometimes hunts on the surface by going in a circular or semicircular pattern to trap and capture her prey. When using this feeding technique, she rolls her body over to a side; most often it is her right side.

Boomerang was seen with a calf in 1990. Due to the lack of biopsy samples and the infrequent number of their encounters together, we cannot confirm her as the calf’s mother.

boomerang

From the bulletin Portrait de baleines, October 5, 2018

Fin whales and blue whales that visit the Estuary feed mainly on krill. From 2007 to 2017, a hydrophone anchored downstream of Les Escoumins recorded the infrasound vocalizations of these two species of whales as well as the concentration of krill present. Researchers Yvan Simard and Nathalie Roy of Fisheries and Oceans Canada published the results of this decade-long monitoring in the journal Le Naturaliste canadien, on the occasion of the 20th anniversary of the Saguenay-St. Lawrence Marine Park. Thanks to these data covering the entire year, i.e. every day regardless of meteorological conditions, these two researchers were able to observe that the presence of fin whales and blue whales has been relatively stable over the years, and that individuals seem to visit the park in greater concentrations in the fall. In winter, or rather as soon as ice forms, there is an almost complete absence of fin whales and blue whales. Unsurprisingly for observers on the water, fin whales tend to have a longer and stronger presence than blue whales. Interannual variability can be distinguished for the two species, though at the present time there does not seem to be any correlation between the presence of these species and that of krill. In fact, the presence of krill is high, and on average, krill biomass was higher in winter, when these rorquals were absent. However, krill concentrations fluctuate significantly over short periods of time, and do not show a strong correlation with semi-monthly tides. It should be noted that links between krill and rorqual concentrations can be difficult to establish, since infrasound detection is carried out over a vast area whereas krill detection concerns a more restricted area.

Learn more:

Fin whale