BOSTON, Mass. — Over the past three weeks, six critically endangered North Atlantic right whales have died in Canadian waters. With only about 500 of these massive plankton feeders still alive, these deaths represent a loss of more than one percent of the entire population in less than 20 days. This unprecedented loss over such a short period of time has alarmed right whale scientists, including those at the Anderson Cabot Center for Ocean Life at the New England Aquarium and the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Mass.
“[I]t is great cause for concern,” said Rosemary Seton, Allied Whale research associate and marine animal stranding coordinator. “This is a highly endangered species, and to have six dead in a short period of time in a particular region is unprecedented.
Mark Baumgartner, an associate scientist at WHOI and chairman of the North Atlantic Right Whale Consortium, said, “This is a right whale mortality disaster. The loss of so many animals so quickly has probably not occurred since right whales were hunted in the early 1800s.”
Last autumn, researchers officially recognized that the right whale population has declined in recent years, caused by reduced birth rates, the highest rate of human-caused deaths ever recorded and changes in right whale feeding areas.
Changes in the oceanographic characteristics of their traditional feeding waters in the Gulf of Maine have led to changes in right whale movements. The right whales’ broader search for copepods, their preferred rice-sized zooplankton, has prompted a search by whale scientists to find other possible feeding areas further north in Canada’s Maritime Provinces.
All six whale carcasses were first sighted in waters north of Prince Edward Island and southeast of Quebec’s Gaspe Peninsula. Aerial survey flights over the past week have spotted dozens of other live right whales still in the region.
One of the dead right whales was found entangled in snow crab gear, but the cause of death of the other five whales is unknown.
“Over the past 30 years, the two leading causes of death for right whales have been vessel strikes and entanglement in fixed fishing gear,” said Amy Knowlton, an Anderson Cabot Center researcher who has worked at reducing human-caused deaths of right whales. Five of the whale carcasses still at sea have yet to show evidence of entanglement or trauma from a collision with a boat or ship.
In other large whale die-offs, humpback whale deaths in the northwest Atlantic were tied to naturally occurring biotoxins associated with red tide algae. However, Anderson Cabot Center scientists who manage the right whale photographic catalog point out that there has never been a right whale mortality attributed to biotoxin poisoning in the nearly 40 years of their study.
The next suspect for such a cluster of unexpected mortalities might be disease. Four of the six right whales have been individually identified through photo comparison by Anderson Cabot Center staff and had not appeared to be in poor health at the time of their last sighting.
The first dead whale spotted on June 6 was a 10-year-old male who was last seen in Cape Cod Bay on April 23 by the Center for Coastal Studies. The elapsed time between those sightings was only about six weeks. The other identified dead whales included two adult males, at least 17 and 37 years old, and a highly valuable 11-year-old female. Through DNA analysis, two of the males were known to have sired calves. The two remaining unidentified whales were a male and a female.
“For a small population like right whales, the difference between population growth and a path toward extinction can be the matter of a handful of animals,” said Scott Kraus, vice president and senior science advisor at the Anderson Cabot Center. “This abrupt loss of reproductive potential in a critically endangered species is a major setback. We greatly appreciate that Canada’s Department of Fisheries and Oceans has gone to such great effort to help retrieve images, tissue samples and carcasses so that we might learn what are the contributing factors to such a wildlife emergency.”