Bp059, A.K.A. “Trou”

Bp059, known as “Trou”(meaning “hole” in french), joined the photo identification catalog of fin whales in the Estuary in 1994.
The average frequency of her visits to the Estuary is more than three years out of four, making it a
“regular” St. Lawrence River. Some fin whales are only occasional visitors, while others remain faithful to their feeding grounds. The recurrence of her visits allows GREMM researchers to study her and learn more about her species. It must be said that Trou is easily identifiable: she owes her name to the hole in the shape of a volcanic crater on her left flank.

In 1996, thanks to a radio transmitter attached to her back, she was followed for 12 hours to study the territory used by fin whales and to evaluate the impact of boats on their behavior. In 2000, the taking of a sample of its blubber (or biopsy) reveals that Trou is a female, which suggests that the calves that accompanied her in 2006 and 2009 could be hers. A calf was also seen in her company in 2020. Repeated observations in July confirmed that it is indeed hers.

In addition to contributing to GREMM’s documentation of fin whales, Trou offers a unique show in 2016 when she plunges with its tail out. This is a very rare behaviour among fin whales.

Bp059 is nicknamed “Trou” (Translator’s note: “hole” in French) in the Marine Park due to the protuberance behind her blowhole on her left flank that resembles a volcanic crater. Her dorsal fin is marked by two notches at both ends; her chevrons show very little contrast. A biopsy taken in 2000 allowed researchers to conclude that Trou is a female. In 2006 and 2009, Trou was seen with a calf. This year again, Trou was sighted with a little one at her side. Keep your eyes peeled, as we will need to observe the calf multiple times at her side over the course of the season to confirm whether or not this offspring indeed belongs to Trou. In 1996, Trou was tracked by radio telemetry as part of a program to study fin whales’ use of the area and to evaluate the impact that boats have on their behaviour. The tag remained in place 12 hours. Trou’s frequent use of the Estuary means that she is considered a “seasonal resident”.

Like the other cetaceans of the St. Lawrence, fin whales frequent the mouth of the Saguenay to feed. They are known for their particularly impressive feeding strategies. Thanks to the use of drones and aerial observations from research groups around the world, we have a better understanding of these fascinating behaviours. We can occasionally see them execute a complete roll-over. Similar to blue whales, fin whales turn on their sides, accelerate and open their mouths by angling their lower jaws to nearly 90° to engulf a volume of water that sometimes exceeds their own volume. In fact, a fin whale’s belly, with its expandable ventral grooves, increases on average 162% in circumference and 38% in length, allowing it to take in up to 80,000 litres of water in just a few seconds. This water is then expelled through the baleen, leaving only prey trapped inside the animal’s mouth. With gulps spaced just over 40 seconds apart, this large rorqual can thus take more than one bite per dive.

The colouration of the fin whale’s jaw is asymmetrical: white on the right side and darker on the left. Some researchers hypothesize that this asymmetry might allow the animal to better camouflage itself when it is hunting large schools of fish. Others believe that fin whales use this particular trait to better disorient their schools of prey when encircling them. Hopefully we’ll have the chance to witness such displays this season!

At last, fin whales are being seen more regularly in the Marine Park! Among them was Bp059, photo-ID’d off Cap de Bon-Désir between Les Bergeronnes and the Paradis Marin campground, and later near Pointe à Pierre-Paul. Bp059 received the somewhat unusual name of “Trou” (French for “hole”) in reference to the protuberance on her left flank behind her blowhole. The cavity at the centre of the bulging outgrowth resembles the shape of a volcanic crater. Trou also has two slight notches in her arched dorsal fin and her back is marked by a discreet dip just in front of the dorsal fin. The light gray markings of her chevron are not strongly contrasting.

Fin whales may occasionally be confused with another species of the same family that sometimes frequents the area: sei whales. The sei whale is often described as a smaller version of the fin whale: 12 to 16 m versus 18 to 21 m. Unlike the fin whale, the sei whale shows no pigment asymmetry in the jaw and baleen. The back of the fin whale is slate gray, while that of the sei whale tends toward dark green, with small white dots under the belly.

This cosmopolitan species is found scattered throughout the oceans of both hemispheres; observations in the St. Lawrence are rare. Thanks to genetic analysis, Marine Mammal Emergencies was able to confirm that a sei whale carcass washed up in Baie-Comeau in 2009.

One feeding habit of the sei whale that is not found in other rorquals is that it often “skims” its prey – even if it has ventral grooves – thus filtering its food as it swims along.

Sei whales, which have been decimated by hunting, are under-studied. Encounters with these denizens of deep waters far from the coast are rare, unpredictable and brief. However, the Falkland Islands (South Atlantic) have been designated as a hot spot for the species, hence the creation in 2016 of the Sei Whale Project in the archipelago, which aims to gather data to better understand these animals.

Trou owes her name to a huge depression surrounded by a blister behind her blowhole on the left side. On her right side, less spectacular characteristics are used to identify her: a rather curved dorsal fin with two quite discrete notches; another depression in front of her dorsal fin breaks the continuous line of her back. Trou lacks the contrasting chevron present in most fin whales.

This year, she was seen for the first time by the GREMM team on June 11. After disappearing from the Marine Park for some time, she reappeared on August 11.

Trou is considered a seasonal resident of the Estuary, as she has been seen more than three quarters of the years since she was first observed in 1994.

Trou was spotted with a calf in 2006 and in 2009, though it is not possible to determine the existence of kinship between them. This three-year interval corresponds well however to the minimum time span between births in fin whales. After a gestation period of 11 to 12 months, calves are born between November and January. The newborn weighs nearly 2 t and measures over 6 m. It is nursed by its mother for 6 to 7 months. Once weaned, the young sometimes seeks the company of an adult, though not necessarily that of its mother.

In winter, fin whales of the North Atlantic – including those individuals that frequent the St. Lawrence – set out for temperate waters to reproduce. Their calving grounds, which are certainly farther south in the ocean, are poorly known, as are their migratory movements. These solitary animals form temporary associations in pairs or in groups. In the 1980s and 90s, groups of several dozen fin whales (up to 40 individuals) were observed in the Estuary.

Since 1986 the GREMM has been managing a catalogue of fin whales of the Estuary, which contains approximately 100 individuals. Fin whales identified in the Gulf – about 450 individuals – have been catalogued by MICS since 1980. In Canada, the conservation status of the fin whale is “Special Concern”.

Video of a breathing sequence of a group of fin whales.