After an algal bloom off Cape Cod was identified earlier this month as a possible cause in the deaths of gannet seabirds on the coasts of Maine and Massachusetts, scientists are now considering whether toxic algae may have caused the death of six North Atlantic right whales in the Gulf of St. Lawrence.
The whale carcasses all have been spotted within the past month floating off the Magdalen Islands, according to Canadian news media reports.
The deaths are of particular concern because of the critically endangered status of the North Atlantic right whale population, which is estimated to number around only 500 animals. Six dead right whales account for more than 1 percent of the species total estimated population.
The population of northern gannets in North America, by contrast, is believed to be approximately half a million, according to the U.S. Fish & Wildlife Service.
The Globe and Mail reported Monday that scientists have taken some samples at sea from the floating whales and have tagged three of the corpses with radio trackers but have yet to tow any of them to land, where they can conduct comprehensive necropsies that may reveal why they died. The Canadian Broadcasting Corp. has reported that entanglement in fishing gear and ship strikes have not been ruled out as possible factors.
The well-being of North Atlantic right whales has received a lot of attention in Maine because of the impact federal regulations aimed at protecting whales has had on the state’s iconic lobster fishery. Rules that govern how lobstermen must configure their gear to decrease the risk of entanglement has had a significant impact on the fishery, which employs thousands of Mainers and produces half a billion dollars of lobster each year.
Earlier this year, U.S. officials said they are investigating a spike in the deaths of humpback whales along the East Coast over the past 18 months. The deaths, some of which have been attributed to ship strikes, come at a time when the numbers of humpbacks in the western North Atlantic have been on the rise, which last fall resulted in the population segment being de-listed from the federal Endangered Species Act.
If toxic algae is found to be behind the deaths of the right whales in the Gulf of St.Lawrence, it would not be the first time that algae has been blamed for killing whales.
From 2005 through 2014, deaths of young southern right whales off the Valdes Peninsula in Argentina spiked into the hundreds. The species, which can be found in the southern Atlantic, Indian and Pacific oceans, has an overall estimated population range of 7,000 to perhaps twice that, though some more regional populations such as off the west coast of South America still are considered to be critically low.
In a scientific paper published in 2015 in the journal Marine Mammal Science, researchers identified the likely culprit as a bloom of the toxic algae Pseudo-nitzschia, some varieties of which can produce domoic acid, a potent neurotoxin that also can affect bivalve shellfish and cause amnesiac shellfish poisoning in people who consume it.
Right whales populations in the northern Pacific and Atlantic oceans each are considered to be a separate species from their southern counterparts because of the whales’ inability to travel through warm equatorial waters that separate Earth’s northern and southern hemispheres.
All right whale species are listed as endangered under the federal Endangered Species Act, as are some other whales species, because of severe population declines caused by centuries of commercial whale hunting.