Scientists scrambling to figure out why Western Alaska chum and chinook stocks are crashing

Scientists have been scrambling to figure out why Western Alaska chum and chinook stocks are crashing. 
They’re starting to hone in on one primary cause for the chum collapse: recent marine heatwaves in the Bering Sea and Gulf of Alaska, alaskapublic.org writes. 
Katie Howard from the Alaska Department of Fish and Game said that’s linked to climate change. There have always been marine heatwaves, but the recent ones are different.
“They were just bigger, they were geographically larger, they were more intense,” said Howard. “And they lasted over a much, much longer period of time than is typical. And so that is what has been tied to a changing climate — that it’s more extreme when it happens. And the other expectation is that they may occur more often.”
But Howard said scientists aren’t exactly sure what’s impacting wild chinook, and that species has been on the decline in many Alaska rivers for a decade now.
Many residents also point to another driver behind the low returns of both species: commercial fisheries in the Bering Sea. State and federal managers have allowed these commercial fisheries to continue to operate, even as they have placed more stringent measures on Yukon River subsistence users.

Alex Shishlo for Rough&Polished