Once rare, Oregon now has a regular hypoxia season — low-oxygen episodes in near-shore ocean waters — analogous to the wildfire threat that visits the state’s forests every year, scientists say.

“It’s been much more prevalent over the past 15 or so years,” Oregon State University marine ecologist Francis Chan said in a news release Thursday. “It’s like a special season out there in mid- to late-summer that we can’t see, but is very important. On land, we get smoke and fires. In the ocean, it’s dead crabs.”

Not surprisingly, it’s an issue that Oregon’s crab industry — the most valuable single-species fishery in Oregon— is attuned to.

“It’s something that needs to be researched and studied to understand what’s happening and see if there’s anything we can do to mitigate or avoid the threat,” Hugh Link, executive director of the Oregon Dungeness Crab Commission, said in an interview.

Ocean oxygen content reached dangerously low levels this summer, Chan said, before a mid-September storm came through the region.

A video released by the Oregon Department of Fish and Wildlife showed crabs in a research trap struggling and dying as low-oxygen conditions developed over the course of just a few days. Dead crabs were also scattered on the ocean floor. The scientists said many fish and marine creatures can react to and escape the low-oxygen conditions, but not all.

“The leading hypothesis for why this is happening is that the ocean is changing,” Chan said. “Warmer water holds less oxygen, for one, but there also may be increased stratification and other factors.”

The OSU release didn’t mention climate change, but scientists say much of the extra heat trapped by greenhouse gases is absorbed in Earth’s oceans. One recent study said the rate of ocean warming has doubled since the early 1990s.

Oregon lawmakers this year passed a bill declaring “ocean acidification and hypoxia severely endanger the state’s commercially and culturally significant ocean resources.” The bill established an Oregon Coordinating Council on Ocean Acidification and Hypoxia, co-chaired by Jack Barth, director of the Marine Studies Initiative at Oregon State.