PLEIADES

A text by Audrey Tawel-Thibert

A column-shaped spout over six metres high, a body reaching up to a phenomenal 27 metres and bluish-gray in colour with dark speckling: even at a considerable distance, it’s hard to be mistaken… it’s the imposing blue whale! The long-awaited return of this giant to our waters is confirmed, with two individuals having recently been seen. It was on July 23, in Les Escoumins, that our research assistant photographed them. The identity of one of them is soon confirmed: it is B197, a female who in fact is featured in the catalogue of St. Lawrence blue whales kept by the Mingan Island Cetacean Study (MICS), under the name “Pleiades”. There’s just one way to recognize her, and that is to carefully scrutinize her colour pattern.

In 2006, telemetric monitoring was carried out on her within the framework of the large rorqual monitoring project. The suction-cup tag, which held for 24 hours, provided insight into her diving behaviour. Then, in 2008, B197 really stirred up the industry and researchers when she returned with a calf… an extremely rare event, as it was just the 17^th blue whale calf documented in the St. Lawrence since 1979!

B197’s visits to our sector have been rather irregular since her first stint here in 1988. Where does she go? She seems to prefer the waters off the Gaspé Peninsula. She was seen in 2004 at Cap de Grosses-Roches, in 2012 off L’Anse-à-Valleau and in 2015 off the northern coast of the Gaspé Peninsula. The migratory patterns of blue whales are still very much an enigma. However, a study led by Véronique Lesage published this year revealed a considerable portion of the seasonal movements of the North Atlantic blue whale population through satellite tracking. The tags deployed in early autumn by the research team, introduced into the fat or the cartilage of the dorsal fin of 24 animals, were mainly aimed at better identifying the areas used by the species in winter to “refuel” and reproduce. Impressive factoid: Symphonie (B244) remained in US waters between mid-December and mid-February, and returned to Canadian waters in mid-March… she travelled a total of 11,918 km during this migration! Substantial results to further shed light on the lives of these fragile mastodons.

Jaw-Breaker, B093 and B197

This week, we present three blue whales that have recently been identified in the Marine Park. Individuals can be distinguished by the color pattern on their backs. Also, in the St. Lawrence, 15 to 18% of these whales show their tails when they dive. This is the case of Jawbreaker: her tail has a white spot that’s easy to identify, but pay attention to the details – she’s not the only one to have a spot there.

B093 is one of the oldest males known to have been identified by the Mingan Island Cetacean Study (MICS) run by Richard Sears. Identified several times in the estuary, in 2012 B093 was seen off the coast of Nova Scotia. This year, it was spotted by several cruisers off Les Escoumins and Les Bergeronnes. B197 is also among the blue whales seen in the Marine Park in recent weeks. As for Jawbreaker, the cruisers’ star was finally spotted. Two other blue whales have also been identified in the Estuary in recent weeks: B275 and B236.

Blue whales are often seen alone. But in the St. Lawrence, they sometimes form more or less stable pairs in early autumn. These associations can last for more than a day, or for weeks on end. According to MICS biopsy monitoring, these are most often male-female pairs. The formation of pairs could be a precursor to reproduction in these animals, which takes place during the winter season. Occasionally, a second male joins the duo and the three individuals take part in what is known as a rumba; the female swims in front and the two males compete to be closest to her. After a race, which can last several hours, one of the males abandons the race and the other becomes the female’s escort. Do these pairs really result in reproduction of both individuals? A difficult question to answer in the short term! In 2010, B093 was observed participating in one of these rumbas.

Last August 20, about two kilometres off the coast of Cap Granite, while the GREMM-DFO team was attentively monitoring the movements of the humpback whale Irisept (Cocotte) after fitting her with a telemetry tag, two other humpbacks and at least three blue whales were spotted nearby. Among them: female blue whale B197.

In 2006, B197 was also the focus of : telemetric monitoring jointly conducted by these same research teams. This monitoring allowed her dive profiles to be documented over a 24-hour period. Over the course of the first day, she alternated deep dives (80 to 100 m) and shallow dives (20 to 40 m), with or without feeding. In the evening, her dives were even less deep (5 to 30 m). During the night, B197 fed essentially at the surface, and in the early morning, deeper and deeper dives were recorded, stabilizing at 80 to 100 m until the telemetry tag fell off.

What was she eating? Probably her favourite prey: krill. Every mouthful counts for this fragile titan, considered to be endangered. In order to afford this species peace and respect in the Marine Park, a 400 m buffer must be maintained during boat-based observations. Members of the Eco-Whale Alliance have even committed to complying with this distance beyond park boundaries.

In the Marine Park this summer: B137 (Chaparal) and B227 (Eperon) were also identified, namely thanks to the constellation of blue and gray spots that cover their bodies. These two individuals are registered in the MICS-managed blue whale catalogue, which includes over 420 individuals identified to date.