New Hope for the Leon Springs pupfish

Endangered Species Bulletin, Dec, 2007 by Nathan Allan, Jennifer Gumm

The Leon Springs pupfish (Cyprinodon bovinus) keeps beating the odds. In spite of threats from hybridization, pollution, and habitat loss, it continues to survive in its desert oasis. Although usually less than 2 inches (5 centimeters) in length, they are not without charisma. During their breeding season, males turn a bright iridescent blue and aggressively patrol their territories with what has been described as a "puppy like energy" (thus the name pupfish). The Leon Springs pupfish was reportedly extinct by the 1950s due to the destruction of its one known habitat, Leon Springs in west Texas. Fortunately, Dr. W.L. Minckley of Arizona State University rediscovered the fish in 1965 in Diamond Y Draw, a small nearby spring system north of Fort Stockton, Texas.

Before the fish was listed as endangered in 1980, extraordinary efforts to prevent its extinction were long underway. In the early 1970s, the Texas Parks and Wildlife Department (TPWD) and the Natural Resources Conservation Service (then called the Soil Conservation Service) teamed up with a private landowner to construct an earthen berm around the source of Diamond Y Spring to divert potential pollution from nearby oil and gas production. However, biologists soon discovered a larger threat to the pupfish. A genetic analysis showed that some of the pupfish had hybridized with sheepshead minnows (Cyprinodon variegatus), a related but invasive species native to the Gulf Coast. They presumably were introduced to Diamond Y Draw by a "bait-bucket" release. In 1976, some of the remaining genetically pure Leon Springs pupfish were taken to the Dexter National Fish Hatchery (now a National Fish Hatchery and Technology Center) in Dexter, New Mexico, to establish a genetic reserve. This action would later prove vital to preventing the species' extinction. (It was among the first species brought to Dexter as a refuge population for native fish, but not the last; the hatchery currently maintains 16 native species.) From 1976 to 1978, biologists led by Dr. Clark Hubbs of the University of Texas applied a fish toxicant at Diamond Y Draw to eliminate the hybrid population, then successfully restocked pure Leon Springs pupfish.

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In 1994, Dr. Anthony and Alice Echelle of Oklahoma State University found that the pupfish in Diamond Y Draw were again hybridized with sheepshead minnows. A second round of intensive recovery efforts took place between 1998 and 2001, involving a large group of partners and grants from the Fish and Wildlife Service and TPWD. The hybrid pupfish once again were eliminated from Diamond Y Draw using a combination of chemical and mechanical means before pure Leon Springs pupfish were repatriated from Dexter. Subsequent genetic assessments have shown the restoration efforts succeeded in reducing genetic contamination to acceptable levels at or near zero.

As if the threat from hybridization were not enough, the habitat is surrounded by active oil and natural gas wells. Fortunately, in 1990 The Nature Conservancy (TNC) purchased about 1,500 acres (about 600 hectares) from Mr. M.R. Gonzales and established the Diamond Y Spring Preserve. Immediately, TNC (led by long-time conservation scientist John Karges) initiated on-site stewardship in cooperation with energy production partners, who granted funds for the land purchase and modified their facilities to provide safeguards against contaminants. A matching grant in the mid-1990s from an energy producer and the National Fish and Wildlife Foundation provided funds to remove some oil well pad sites and access roads that had impeded natural surface water flow. More recently, TNC was awarded a Recovery Land Acquisition Grant from the Fish and Wildlife Service and expanded Diamond Y Preserve to more than 4,000 acres (over 1,600 hectares).

Using video surveillance, Dr. Murray Itzkowitz of Lehigh University investigates the fascinating world of social and breeding behavior of the Leon Springs pupfish. He has observed that large territorial males defend areas on rocky shelves in shallow open water. Intermediate- and small-sized males act as "satellite breeders" by sneaking in to mate with females while the territorial male is occupied with fending off neighbors or courting other females. Females then enter the male's territory to spawn. The female lays a single egg at a time, but will repeat the sequence many times before she leaves the territory for another male or leaves the breeding shelf altogether. As many as 25 territorial males can pack into a 30-square-foot (3-square-meter) area. Territorial males also show complex communication among each other known as "dear enemy recognition." This is where territorial males show less aggression to familiar neighbors than to strangers.

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Other research continues to monitor genetic integrity, as well as document genetic diversity in the wild and captive populations of Leon Springs pupfish. Maintaining high levels of genetic variation is important to the species' recovery objective of ensuring self-sustaining, genetically-uncontaminated populations in Diamond Y Draw.