Scientists from a New England aquarium have spotted North Atlantic right whales in waters south of Massachusetts this month, prompting federal authorities to designate a voluntary slow zone. Anderson Cabot Center for Ocean Life scientists saw the whales during two different aerial surveys south of Nantucket: Scientists say at least 23 unique whales have been identified so far, including two females that have calved in recent years and a young adult female who may be nearing calving age. “These three females were all seen in surface active groups, a social behavior that involves several right whales closely interacting at the surface. These surface active groups can also provide mating opportunities, although not always,” reads a news release from The New England Aquarium. Assistant scientist Kate Laemmle, who was one of the observers aboard the survey plane, says the whales were “rolling, splashing, and bursting out of the water.” “Seeing these critically endangered right whales on our first surveys of the New Year is a great way to start the season and leaves us hopeful for more whales returning to the area,” she said. The whale sightings near Nantucket triggered a voluntary slow speed zone, in effect until Jan. 20, for mariners to reduce their speed to 10 knots to protect the whales. It is one of several active voluntary slow zones from Massachusetts to Virginia. “Vessel strikes are one of the leading causes of injuries and deaths for this species, which numbers about 380 individuals, making it critical that vessels slow down to the recommended speed,” reads the release. The winter/spring season is the peak time of year for right whale sightings in southern New England waters. Right whales have also been spotted in Cape Cod Bay over the last month. The area is subject to a mandatory slow zone for boats and ships, known as a Seasonal Management Area, until May 15. The aerial surveys conducted by the New England Aquarium help monitor changes in animal populations, identify various species, recognize trends using standardized data, and monitor aggregations.