BUZZARDS BAY — A pair of North Atlantic right whales swimming in the Cape Cod Canal led Army Corps of Engineers officials to close the waterway for four hours Monday.
The endangered marine mammals were spotted in the canal shortly after 9 a.m., Dennis Arsenault, an Army Corps marine traffic controller, said Monday. Two government ships were sent out to keep tabs on the whales, which were last seen heading east in a strong current near the Sagamore Bridge, most likely exiting into Cape Cod Bay, Arsenault said. The canal was reopened at 1 p.m.
The right whales are considered endangered under the federal Endangered Species Act. Fewer than 500 remain in the world, according to Whale and Dolphin Conservation Society communications manager Karen Urciuoli. The conservation society, which has offices in Plymouth, was not directly involved in the sighting.
"This is about the time we start to see right whales in Cape Cod Bay," Urciuoli said Monday. "In the past few years, there's been about one sighting in the canal a year. It's really fantastic for them to spot them and shut the canal, to restrict the traffic. One of the leading dangers to the North Atlantic right whale is ship strike."
Closing the canal when right whales are spotted is standard operating procedure because of the whales' scarce numbers. The canal is 14 miles long and typically sees about 20,000 ships pass through its waters each year.
Since Nov. 30, right whales have been seen in the bay by spotters for the conservation society, Urciuoli said. A handful of right whales were seen in mid-December off the coast of Provincetown, according to the Provincetown Center for Coastal Studies.
The majority of the western population of North Atlantic right whales spends winters calving in coastal waters off southeastern U.S. lands. The whales move north to New England, the Bay of Fundy and beyond for summer feeding and nursery grounds.
Massachusetts Bay and Cape Cod Bay are designated by the federal government as areas of "high use" for right whales and a primary habitat.
In December 2008, the Cape Cod Canal was closed for 2½ hours because one right whale swam east to west through the canal, exiting at Buzzards Bay.
Before that, the last one to traverse the canal was seven years previous, according to a Center for Coastal Studies spokesman.
Staff writer Steve Doane contributed to this report.