BOISE, Idaho (AP) — Northwest fisheries managers are creating a response plan should there be a return of warm water conditions biologists say was the main factor in killing some 90 percent of adult sockeye salmon returning to the Columbia Basin last summer.

The report this spring will suggest ways to cool water temperatures that became lethal for most of the 510,000 sockeye that entered the Columbia River basin to spawn. But Ritchie Graves with the National Oceanic and Atmospheric Administration says options are limited.

In related action, a coalition of environmental groups in a February letter to the U.S. Army Corps of Engineers says massive fish kills put federal managers at risk of violating the Endangered Species Act. Thirteen populations of salmon and steelhead are listed as endangered or threatened in the basin.