Researchers at the Whale Center of New England said they observed the mammoth sea mammal for about 45 minutes Sunday while it was believed to be feeding on a localized prey source, likely plankton, WCVB-TV, Boston, reported Monday.

Staff at the Whale Center said photos taken of both sides of the whale will be contributed to an ocean-wide census of more than 300 blue whales that was coordinated by Canadian whale researchers.

The researchers said the whale was seen near about a dozen feeding humpback whales.

Blue whales are the largest mammals on the planet. The largest blue whale on record was 102 feet long.