Interesting article on OPB yesterday about the decline of mega-Chinook. Our official position at OFFB is that the sole mammal species responsible for salmonid declines is sitting behind our keyboards. But there is some interesting stuff about orca biology here.
A study from federal researchers in November found that orcas’ consumption of chinook salmon in the Northeast Pacific Ocean has doubled since 1975, surpassing humans’ catches, which have fallen by a third over that time.
“There is a large number of resident killer whales out there that really target chinook, and they target the large chinook,” Ohlberger said.
“As far as we can see, the killer whales are taking the older and bigger fish,” said Craig Matkin, a whale researcher with the North Gulf Oceanic Society in Homer, Alaska. Matkin, who was not involved in Ohlberger’s paper, studies Alaskan orcas’ diets.
“They’re going to go for the biggest, oiliest fish there are,” Matkin continued. “That’s chinooks.”
Salmon born in Oregon and Washington spend most of their lives out at sea, often in Alaskan waters, where orcas aplenty await.
“Our [orca] populations have increased faster than anywhere else, and they’re eating chinook from all over the place,” Matkin said.