by Rick Black

Utah Lake is an 11,000 year old natural lake remnant of Lake Bonneville that has been modified by man into an operational water supply reservoir – the result of a dam built in 1872 at its natural outlet to the Jordan River in north Utah County. (USFWS, 2010). Historically and today, Utah Lake is the main source of water for the local population. However, today’s Utah Lake barely resembles the healthy ecosystem of the past – overrun by an introduced species, the Common carp. Utah Lake was essential for community and cultural development during the settlement of northern Utah. A thriving unaltered ecosystem supported millions of fish, a multitude of species of birds and animals thrived, as well as the surrounding habitats. (Carter, 2002).

The once pristine and calm lake began to change dramatically with the introduction of the Common carp (Cyprinus carpio) in the 1880s. The U.S. government introduced the carp as a replacement species due to the decline in native species from overfishing. The idea was to replace dwindling numbers of Bonneville cutthroat trout and provide locals with hardy fish that were popular in other areas of the world (Carter, 2002). However, the introduction of carp resulted in a loss of aquatic vegetation from foraging and increased sediment mobilization into the shallow water column. Before the carp were introduced, vegetation prevented lake bed sediments from stirring and plants (from single-celled to large plants) could photosynthesize in the clear water. With the introduction of the carp, nutrients previously sequestered in the sediment were more easily mobilized, creating hyper-nutritious conditions which favor the algal population. Higher algae concentrations increase the possibility for undesirable algal blooms and low oxygen conditions that could contribute to fish kills.

Such conditions were detrimental to the native fish species and further favored the carp population. The water became more turbid from ‘rooting’ of the carp through the bottom sediments and this reduced photosynthesis, plants died and habitats for small fish and insects were lost, the lake transformed from a clear water state rich in biodiversity to one of turbid green dominated by carp. Furthermore, the impacts to the water quality and aquatic ecology were exacerbated by the use of the lake as a receiving body from agricultural, industrial, and municipal activities. From the 1890s to 1950s, raw sewage was also dumped into Utah Lake. Utah Lake became nearly abandoned by locals for recreation as the aesthetics and the water quality decreased.

In an effort to restore the lake, in about 2011 the Utah Division of Wildlife Resources and the Utah Lake Commission began removal of carp (over 13 million pounds to date). In 2013 they conducted an analysis of the removal of Common carp from Utah Lake.  Continued carp removal (need to remove 18 million additional pounds over three years) would require an investment of just over $5 million over the next 20 years (including maintenance costs).  (Ecosystem Valuation of continued carp Removal of Utah Lake” Utah DNR, Utah Lake Commission, March 2013) However, when compared to the value of the increased ecosystem services of carp removal, the results were staggering. Recreational fishing estimated benefits are expected to exceed $90 million discounted over twenty-years from services such as fishing, non-fishing recreation, property values and taxes. These estimated values only consider water quality improvements from carp removaland do not include other benefits that are part of the larger management plan for Utah Lake such as shoreline restoration and improvements to recreational trails, beaches, and other amenities. Also not included in the valuation analysis were: value of restoring T&E habitat for the endangered fish, the June Sucker, water quality improvements in the receiving bodies of the Jordan River and the Great Salt Lake and other ecosystem services that would be restored.

Additional benefits from restoration of these services and local native shoreline vegetation restoration are likely to add significantly more benefits than what were estimated by simply removing 75% of the biomass of one bottom-feeding species, in a shallow fresh water lake. “If we get funding to finish this project, in the next three years we should see a different Utah lake out here,” said Chris Keleher, Deputy Director of Recovery Programs for the Department of Natural Resources. “This is by far and away the biggest project of this type that has ever occurred in the world — and if we’re successful then it’ll be something to be really proud of,” Keleher said.

Introduced species are a problem globally, they can significantly alter the once-pristine system into which they were introduced. They can have great impacts to the local populations who rely on the services derived from the healthy ecosystem. In Utah Lake, the removal has been successful for years, and the funding needed to complete the removal and manage the system is negligible in comparison to the values of the services restored. Utah Lake is a successful example of using the economics of an action to encourage moving forward with solutions.