Southern California’s Imperial Irrigation District, which supplies water to farmers who grow most of the nation’s winter vegetables, planned to start a conservation program in April to scale back what it draws from the critical Colorado River.

But a tiny, tough fish got in the way.

Now, those plans won’t start until at least June so water and wildlife officials can devise a way to ensure the endangered desert pupfish and other species are protected, said Jamie Asbury, the irrigation district’s general manager. The proposal to pay farmers to temporarily stop watering feed crops such as alfalfa this summer has environmentalists concerned that irrigation drains could dry up, threatening the fish that measures the length of an ATM card.

“Drains are created for farmers to be able to convey irrigation runoff, and the pupfish decided it was a good place to live,” Asbury said.