Charlie Lean easily recalls when he realized that big changes were sweeping the fish stocks along the northern shores of Alaska. Just over 10 years ago, when Mr. Lean was the state’s fisheries manager for the northwest region, a call came in from the tiny Eskimo outpost of Kivalina, on the Chukchi Sea 150 miles northeast of the Bering Strait. A village elder was reporting “a massive fish kill” in the Wulik River, Mr. Lean said. Everyone assumed it was from some toxic spill upriver at the giant Red Dog zinc mine.

“I rounded up a plane and blasted off and flew up there,” he said. “Flying overhead I could see right away it was the end of a pink salmon run. They were dying of natural causes as they always do once they spawn.”

The elders had never seen a run of this salmon species. But they have shown up every year since.

The colonization of new rivers by pink salmon is just one of many changes in fish and crab stocks that appear linked to retreating sea ice and warming waters in the Chukchi Sea and, farther south, the Bering Sea. The changes are important because the Bering is rich with pollock, salmon, halibut and crab, already yielding nearly half of America’s seafood catch and a third of Russia’s.

Recent studies have projected that in a few decades there could be lucrative fishing grounds in waters that were largely untouched throughout human history.

In a 2002 report for the Navy on climate change and the Arctic Ocean, the Arctic Research Commission, a panel appointed by the president, concluded that species were moving north through the Bering Strait. “Climate warming is likely to bring extensive fishing activity to the Arctic, particularly in the Barents Sea and Beaufort-Chukchi region where commercial operations have been minimal in the past,” the report said. “In addition, Bering Sea fishing opportunities will increase as sea ice cover begins later and ends sooner in the year.” Read more….