The critically endangered fish live in the upper 80 feet of a deep water-filled cavern, which makes it the smallest range of any vertebrate species on the planet, according to officials. The area is a detached unit of Death Valley National Park, near Ash Meadows National Wildlife Refuge in Nye County.

The count is seasonal, and the highest since Sept. 2003. Decades ago, the count was around 400 to 500 in the fall.