Science policy of the Endangered Species Act: The little fish story

Once upon a time, large lakes and rivers covered the southern Nevada region. As the climate warmed, these water sources began to dry up. Aquatic species were isolated; among them, a small fish species is believed to evolve into several different species over time. These fish use the remaining small seeps and springs created by groundwater discharge as their homes. Now, they are one of the rarest aquatic animals, and their homes are bounded by desert.

This is the story of the pupfish; one of these species was designated for protection even before the ESA. With a maximum size of less than 3cm long, they are powerful players in determining water distribution in one of the highly contested areas.

During spring break, I went to Las Vegas (for birding), and took a trip to see this amazing little fish. They are beautiful, watch the video and photos to see if you agree.

The place I visited is called the Ash Meadows Complex. Ash Meadows is home to 26 endemic plants and animals species, including three endangered pupfish species (the Devils Hole Pupfish, the Ash Meadows Amargosa Pupfish and the Warm Spring Pupfish) and seven threatened plants.

I’m going to share the information I learned from the visit in this and the next posting. This one will talk more about the species. The next one will discuss the politics about its protection, and my reflection of the subject.

Among the three pupfish species, the Devils Hole Pupfish is the most famous. It is the smallest of all, only 2.5cm long. Their typical life span is only 6 to 9 months, and they reach sexual maturity in 3 months. They live only in this small deep hole (actually a water-filled cavern cut into the side of a hill) with water about 500 feet deep. The water temperature remains constant at 92OF; the fish stay close to the water surface, and travel only as deep as 66 feet.

From a conversation with the ranger who gave guided tours just outside the hole, I learned that scientists are alarmed by a sharp decline in the fish population. Scientists have been monitoring the population, and recorded a peak population of over 500 fish in the mid-1990s. By 2004, the population had plummeted to 210 adult fish. The last count they did in early this year, only 38 fish were recorded, and that translated to an estimate of 100 fish total.

There are two explanations for the decline. First, there could be a lack of algae, the primary food source of the fish. The algal growth depends on the amount of sunlight and the concentration of nutrients in the water. Nutrients in the water are driven by the pellets dropped from the barn owls which use the hole as roosting or nesting site. Simply put, the decline in barn owl population may have a direct effect on the fish population. Second, climate change could be the reason. This explanation is yet to be proved, but it is not hard to believe that global warming is impacting the ecosystem without us even realizing the changes.