National Geographic : 1995 Oct
A Desert Realm of Fish SA small valley in the Chihuahuan Desert, Cuatro Cienegas harbors within its 500 or so square miles one of the world's rare inland-desert wetlands. Underground water some warm, some cool, most of it highly mineralized flows to the surface through a little-understood system of subterranean channels, prob ably from deep aquifers. While human beings have been exploiting this water for centuries, only recently have biologists discovered that an amazing number of other species have been exploiting it as well. When I first came here in 1978 to photograph box tur tles, the count was not in. Now more than 60 species found only here have been identified, ranging from cac tuses to snails, scorpions, fish, and reptiles. What's more, hundreds of nonen demic species make the val ley a biological garden. Where there is water, so are there fish-in the lagunas (lakes), in the pozas (pools), and in the many canals, such as those tapping the blue wa ters of Pozas Azules (bottom right). Countless pozas are natural aquariums, with only a few hundred gallons of wa ter. Even the larger lagunas are seldom more than 250 feet wide or 25 feet deep. In Poza de la Becerra-"pond of the young calf"-tetras swirl about diver Jesus Lopez.