An estimated 22,000 trout have been killed this year along a 15-mile stretch of the Guadalupe below Canyon Dam toward New Braunfels, according to the Texas Parks and Wildlife Department.
Fire ants are toxic to the fish.
Some trout had as many as 500 ants in their stomachs, officials said. Andrew Labay, regional pollution biologist with the wildlife department, said fire ants go on mating flights after the first strong rain every May. From 3,000 to 4,000 winged ants per mound take to the air to continue their species, he said. The males die and fall to the ground. The females land and start new colonies.