Gulf of St. Lawrence Fin Whale sightings

During the last two seasons large concentrations of fin whales have been observed in the Mingan Island-Anticosti Region. The 2004 season was characterized by dense aggregations of individuals (up to 60 finbacks observed in a single day) consistently located in a small area south of Riviere-au-Tonnerre. In 2005, fin whales were more dispersed throughout the Jacques Cartier Passage, which tends to be the norm. This season was marked by an unusually high number of calves. Until now, the average number of calves per season was two to three, but we identified eight cow/calf pairs this season: six in Mingan, one off Matane, whose mother had been previously seen off Mingan without her calf, and one in the St-Lawrence Estuary. One calf was found beached near Mingan, lying on its right side, which prevented identification. Comparison of a skin sample taken from this dead calf may enable us to make a genetic match with one of the samples taken of the 5 calves biopsied at sea this season. It is interesting to note that 2005 was also a record year for numbers of humpback calves in the Gulf of St. Lawrence. Could the increased number of calves in 2005 be correlated with a generally greater abundance of food detected throughout the 2004 season?

Until recently year to year re-sighting of finback calves had been hampered by the poor quality of their identification photographs. However, our studies and those of researchers in the Gulf of Maine have demonstrated strong site fidelity in adult fin whales and have found that fin whales return each year to the same feeding grounds they first visited as a calf. One of only two calves identified in the St. Lawrence in 2003 was re-sighted there in 2004. We hope to encounter some of the 2005 calves next season.

The high number of finback sightings over the last two seasons led to increased numbers of photo-identified individuals, with 120 and 140 IDs for 2004 and 2005 respectively. However, a good amount of matching needs to be completed for these years in order to eliminate internal matches and arrive at an accurate final count of individuals. Thus far 70 individuals photographed in 2005 have been matched to our fin whale catalogue, 20 new ones have been added (now containing 380 individuals), and as many as 40 additional individuals may be added once the matching is completed. It was interesting to note the presence of several whales that had not been photo-identified in the area for 12-13 years. One wonders if we simply missed them during all these years, or do they frequent the area irregularly? Movements of fin whales between the Gulf of Maine, Nova Scotia and Gulf of St. Lawrence have been documented, but only for a very small portion of the Western North Atlantic population. A few fin whales from the Gulf of Maine may occasionally enter the Gulf of St. Lawrence, which could explain the large time intervals between sightings for certain individuals. We still, however, have a great deal to learn concerning the dispersal of this species in eastern Canadian and New England waters and how it uses the varying habitats it encounters over its range.

The large number of finback IDs collected over the last two years reflects the many study sites we cover as well as the number of fin whales that visit the St. Lawrence in summer. Though our principal study site is the Mingan/Anticosti Island region our mobile team also covers the Estuary and the Gaspe Peninsula, where we search for blue whales, as well as humpbacks and fin whales. At least two finbacks were seen both off Mingan and Matane in 2005, and one of these was actually sighted later in the Estuary. This suggests that some fin whales forage over a large portion of the St. Lawrence during the feeding season even if the majority identified in Mingan occur there recurrently throughout the field season. Finbacks seen in Mingan are also known to use the Sept-Iles area, though in smaller concentrations, as indicated by Jacques Gelineau’s sightings and ours.

In addition to studying the population dynamics and distribution of fin whales in the St. Lawrence, MICS is interested in their social and acoustic behavior. Next season, Julien Delarue, a MICS team member for the last five years, will start a study on the acoustic behavior of finbacks as part of his Masters’ thesis. A more detailed description of the project will be posted in March 2006.