FOOD-SALMON-SHRINKAGE-GET

Joseph John Jr. washes freshly caught salmon with his son, Jeremiah John, while waiting for the tide to come in, in Newtok Andrew Burton/Getty Images

At OBI Seafoods, a sprawling operation with outposts throughout Alaska, there’s all sorts of extra machinery for workers to master. At Whole Foods Market, there are new guidelines for purchasing salmon from wholesalers. And at Ivar’s, a fixture on Seattle’s waterfront for eight decades, the chef is sending back skimpy salmon delivered to his kitchen.

Behind all these changes is an alarming trend that’s been building for years: The giant schools of wild Pacific salmon that can turn southeast Alaska’s ice-cold waters into a brilliant orange blur are thinning out, and those that do survive are shrinking in size.