Something happened to the population of North Atlantic right whales in the last decade, as their numbers shrank and fewer calves were born.

Scientists had long speculated that a change had occurred in the whales’ sources of food. By 2017, only 411 animals were counted, down from 482 in 2010. A paper published this month in the journal Oceanography, links warming in the Gulf of Maine with the life cycle of the copepod Calanus finmarchicus, a tiny shrimplike creature that forms the foundation of the right whale diet.

Although it is hard to prove cause and effect, the paper’s lead author, Nicholas Record, said the study connected “the big ocean-scale climate changes” in the North Atlantic with the water coming into the Gulf of Maine and the whale’s food resources.

“All of these pieces lined up together really well,” said Dr. Record, senior research scientist at the Bigelow Laboratory for Ocean Sciences, a nonprofit institute in Boothbay, Maine. “It was really kind of stunning.”