Jeffreys Ledge is a “very productive area for marine life,” so it’s not surprising that it attracted an unusually large number of the critically endangered species, O’Brien said.

Jeffreys Ledge is east of Portsmouth, New Hampshire. In a Friday evening announcement, Keliher urged fishermen to remove gear that is set deeper than 300 feet from the surrounding area.

A group of about 75 endangered North Atlantic right whales was spotted off the western edge of Jeffreys Ledge. That's about 20 percent of the surviving population.

Jan. 15—Dozens of North Atlantic right whales are gathered off Jeffreys Ledge, east of Portsmouth, New Hampshire, triggering a slow zone for boaters. Surveyors at the New England Aquarium ...

"The area of Jeffries Ledge is an area that is heavily fished, but it's not an area that consistently has large numbers of whales, like definitely not 70 whales every January," she said.

The whales were just off the western edge of Jeffreys Ledge, “a raised underwater area along the coast of New Hampshire and Maine that brings whales, fish and fishers together,” officials said.

"The area of Jeffries Ledge is an area that is heavily fished, but it's not an area that consistently has large numbers of whales, like definitely not 70 whales every January," she said.