Wildlife Finds: Pecos Pupfish
Photo: Pecos pupfish under observation. Andrew Cannizzaro, CC BY 3.0 , via Wikimedia Commons.
In the harsh climes of the Chihuahuan Desert, adaptability is a virtue, and the Pecos pupfish (Cyprinodon pecosensis) has this in spades. Found occasionally in warm-water tributaries of the Pecos River through New Mexico and Texas, this small fish (usually around an inch or two long) is most prominent in the saline springs, sinkhole lakes, and other isolated bodies of water around the Bitter Lake National Wildlife Refuge.
While they were once a common species in the Pecos River itself, many of these populations have mixed with other small fish like minnows, essentially disappearing from the Pecos. Over the years, monsoon floods, changing river courses, and other events may have carried small populations to the isolated ponds they live in today. With the ability to transition from saline to fresh water with little stress, these fish have a unique capacity for carving out new niches in whatever ecosystem they find themselves in.
Pecos pupfish also have unique tolerance to factors like temperature and oxygen levels in the water, altering their reproductive systems and habits greatly to give a better chance for survival into the next generation. Unfortunately, the years have not been kind to the pupfish population in the Pecos and these unique traits haven't been enough to make the species rebound to past numbers.
In the 1980s, several non-native fish species were introduced to the Pecos River, which hybridized with and outcompeted pupfish rapidly. Algae blooms and other ecological factors have caused mass die-offs, further pushing this species out of its home turf, making it a threatened species in both Texas and New Mexico.