From the Cortez Journal (Reid Wright):
Unlike sport fish introduced from outside sources, native species have been swimming local rivers for an estimated 2 million years. But the past few decades, they have become not only low on the food chain, but low on the water chain after water is prioritized for irrigation, industry, drinking water and recreation.
This year, after a winter of below average precipitation, water officials will be releasing a trickle of spill water a little early from the cold bottom of the McPhee Reservoir before the spring rafting spill in an effort to keep water temperatures low during warm spring weather and prevent native fish from spawning too soon…
“The problem is when you get a really rapid rise in temperature very quickly, and then these fish start to mature, there are eggs, and they start to get in spawn mode,” said Jim White, an aquatic biologist with Colorado Parks and Wildlife. “Then the spill [for whitewater enthusiasts] comes along and that water temperature just plummets. That can be very hard on the newly hatched larval fish.”
Recognizing that a threatened or endangered species designation for the native fish could bring government intervention and regulation of the river, whitewater boating organizations have agreed to sacrifice some spill water for the fish, said Mike Preston, manager of the Dolores Water Conservancy District.