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US Fish & Wildlife Service FieldNotes

CARLSBAD FWO: Desert Pupfish and the Salton Sea's Experimental Research Ponds

Region 8, August 31, 2010
Juvenile desert pupfish in net. (USFWS/Carol A. Roberts)
Juvenile desert pupfish in net. (USFWS/Carol A. Roberts) - Photo Credit: n/a
Sharon Keeney, California Department of Fish and Game, sorting through desert pupfish to remove exotics before transport. (USFWS/Carol A. Roberts)
Sharon Keeney, California Department of Fish and Game, sorting through desert pupfish to remove exotics before transport. (USFWS/Carol A. Roberts) - Photo Credit: n/a

By Stephanie Weagley and Carol A. Roberts, Carlsbad FWO

When Carol Roberts, Division Chief of Coachella and Imperial Valleys for the Carlsbad Fish and Wildlife Office (FWO), was asked what one of her most memorable experiences she had while working for the Service in 2010, she replied, “The desert pupfish rescue at the Salton Sea.” What she was referring to was the decommissioning of experimental research ponds located at the south end of the Salton Sea in Imperial County, California.

The project, built in spring of 2006 by the U.S. Geological Survey (USGS) and the Bureau of Reclamation (BOR), was originally developed to examine the possibility of creating shallow-water saline ponds as habitat for shorebirds. Four ponds were created in an area that had once been flooded by the Salton Sea, but now are above the current shoreline. Pond designs included islands to see if any specific configuration was more attractive to nesting birds and water was taken from the Alamo River and mixed with saline water from the Salton Sea to help fill the ponds.

“Then in April 2007, it was discovered that desert pupfish occupied the experimental ponds despite our efforts to exclude them,” said Roberts. “We do not know how the desert pupfish turned up in the ponds. But, regardless of how, the discovery provided scientists a unique opportunity to learn more about this species. It provided an opportunity to better study how factors such as water temperature, dissolved oxygen, salinity, and interactions with other fish species affect the pupfish.” At this time, it was estimated there were approximately 1,000 pupfish in the ponds.

Populations of naturally occurring desert pupfish (C. macularius) are only found in two stream tributaries to, and in shoreline pools and irrigation drains of the Salton Sea in California and in Mexico. They are small fish, less than three inches long that feed on small aquatic invertebrates and crustaceans, including insect larvae, worms, snails, as well as plants, and detritus; they are a federally endangered species.

Desert pupfish grow rapidly, have short-lives, and can complete their life cycle in a single summer under good conditions. They are a remarkably adaptable species and can survive in aquatic habitats with high temperatures and salinities. But despite their adaptability, desert pupfish in California are found only in small isolated populations.

Upon learning that funding for the operation would not be renewed in 2011, necessitating the decommissioning of the experimental ponds at the Salton Sea, the BOR began working with USGS, Carlsbad FWO and California Department of Game and Fish (CDFG) in June 2010, to plan and execute a shutdown.

Before the water could be shut off, a large multi-agency effort was undertaken to rescue and relocate the fish managed by the CDFG and staffs from the BOR, USGS, FWS, and the Imperial Irrigation District.

“The scale of the rescue and relocation turned out to be absolutely huge in terms of numbers of pupfish,” said Roberts. “Over 1 million pupfish were saved in the effort. Everyone involved immersed themselves in the tasks at hand to ensure that the rescue could proceed quickly and efficiently. That included everything from coming to the site, physically moving pupfish, providing logistical support (pump operations, a refrigerated truck for holding pupfish, gathering miscellaneous supplies), and doing the necessary paperwork. It was all about the pupfish, not egos or agency positions.”

Rescued desert pupfish were distributed to a dozen drain habitats surrounding the Salton Sea and to various refugia ponds in southern California near Anza Borrego Desert State Park, Dos Palmas Preserve, Oasis Spring Ecological Reserve, Salton Sea State Recreation Area, and the Living Desert.

A shutdown of the experimental pond operations occurred in August 2010. During the project’s operational period, four years, USGS scientists evaluated bird use of the ponds, nesting activities, and the unexpected added bonus of studying desert pupfish.

The Salton Sea, California’s largest inland lake, supports an abundance of natural resources, including a spectacular bird population that is among the most concentrated and most diverse in the world. It is a crucial stopover for wintering and breeding waterbirds along the Pacific Flyway with more than 400 species of birds using this ecosystem, which includes several federally listed species.

It also faces an uncertain future. The Salton Sea is approximately 35 miles long, 15 miles wide, and 50 feet deep with a surface elevation of about 230 feet below sea level. Since its formation by Colorado River flood waters in 1905, salinity levels have continued to rise.

Most of the Salton Sea’s inflow currently comes from agricultural drainage from the Whitewater, New, and Alamo Rivers. Water leaves the Salton Sea by evaporation as there are no outflowing rivers or streams.

Not only is the water’s salinity rising, but various environmental problems exist within the watershed and include water delivery reductions scheduled to take place by 2018. With the scheduled water reductions, this will further decrease the agricultural flow into the Sea. The combination of all these factors is predicted to result in the degradation and loss of aquatic and wetland habitat, lower lake levels, increased salinity, and loss of invertebrate and fish species.

The protection and enhancement of existing habitats including shoreline pools, agricultural drains and natural creeks in the Salton Sea watershed are necessary for many wildlife species using its resources, including the desert pupfish in California.

Restoration and conservation planning programs, as well as developments in future water management have been and are being addressed – the experimental ponds project was one such example. However, it will take the work of many partnership efforts from federal, state, local, and non-governmental entities to help maintain the Salton Sea’s ecosystem for the biological resources dependent upon it.


Contact Info: Stephanie Weagley, 805-644-1766, stephanie_weagley@fws.gov