Researchers from the Northeast Fisheries Science Center (NEFSC) in Woods Hole, Massachusetts, have identified 187 individual North Atlantic right whales in the Gulf of St. Lawrence during the summer. The whales comprise about 40% of the entire catalogued North Atlantic right whale population. The study was published in November in Endangered Species Research.
The team used photographs of right whales collected during whale surveys conducted between 2015 and 2019. The whales were identified by unique patterns of the rough patches of tissue, called callosities, on the top and sides of their heads. Other researchers deployed underwater hydrophones throughout the Gulf. They detected an increase in right whales in some areas beginning in 2015.
Many of the right whales remain in the area through the summer and autumn, feeding and socializing primarily in southern parts of the Gulf. Most of the 187 right whales return to the Gulf every year and stay for up to five months.
Their travel route is not without peril. The northern and southern regions of the Gulf of St. Lawrence are separated by the Laurentian Channel and Honguedo Strait. These shipping corridors connect commercial vessel traffic from the Atlantic Ocean to the St. Lawrence Seaway and the Great Lakes.
Leah Crowe, a NEFSC marine mammal researcher and lead author of the study, noted that during the last decade right whale distribution and habitat occupancy patterns have become less predictable. The whales spend less time in places where they have typically aggregated and are showing up in places where they were not found before.
Between about 1980 and 2010, many right whales spent the spring in Cape Cod Bay and waters off Cape Cod. During the summer, they moved north into the northern Gulf of Maine, Bay of Fundy, and Roseway Basin to feed on copepods and court. The historic patterns, however, began to change in 2010.
Continuing aerial and underwater surveys have confirmed right whales in larger numbers in the Gulf of St. Lawrence during the summer and with few in the Gulf of Maine. The surveys also documented an increase in the numbers of right whales using Cape Cod Bay in the late winter and spring; right whales also occur south of the islands of Martha’s Vineyard and Nantucket almost year-round.
Other interesting finds from the study are that in general, individual whales did not travel far each day while present in the Gulf of St. Lawrence. Some individuals spent time in both the northern and southern parts of the Gulf of St. Lawrence, and pregnant females were among the animals moving back and forth between northern and southern areas.