A judge has asked U.S. biologists to explain part of a determination that a trout native to Colorado and New Mexico doesn't merit an endangered species listing.
But U.S. District Court Senior Judge Marcia S. Krieger found that a 2014 decision by the U.S. Fish and Wildlife Service not to list the Rio Grande cutthroat trout was otherwise sound.
The Center for Biological Diversity sued the agency after it changed course from a 2008 finding that the trout merited protection.
In a ruling issued Thursday, Krieger vacated part of the 2014 decision. She ordered the agency to explain why it considers isolated trout populations of less than 2,500 to be stable.
The Rio Grande cutthroat was the first North American trout to be recorded by Spanish explorers centuries ago.