Teach the Earth > Complex Systems > AGU Modeling Workshop 2010 > Modeling Exercise Ideas > Impact of climate change on endangered fish population in Pyramid Lake

Impact of climate change on endangered fish population in Pyramid Lake

Karletta Chief, Hydrologic Sciences, Desert Research Institute

Topic: hydrology, ecology
Course type: Graduate level course


Pyramid Lake
Pyramid Lake is located approximately 40 miles northeast of Reno, NV on the Pyramid Lake Paiute Reservation. Pyramid Lake is 15 miles long, 11 miles wide, 350 feet at its deepest point, and with a surface area of approximately 112,000 acres, it is one of the largest natural lakes in Nevada. It is also one of the largest remnants of the ancient Lake Lahontan, the colossal inland sea that covered most of
Nevada. The lake is widely acclaimed as one of North America's most beautiful desert lakes and the world class fishery has brought Pyramid Lake worldwide fame. Pyramid Lake is the only habitat in the world for the endangered cui-ui (Chasmistes cujus) fish that existed for over 2 million years. The Pyramid Lake fishery also includes the threatened Lahontan cutthroat trout (Oncorhynchus clarki henshawi) that grow to record sizes and have lured fisherman from around the world over for several decades. Celebrities, foreign royalty, and even a US President have fished the lake in hopes of catching trophy fish at Pyramid Lake (http://www.pyramidlake.us/). The Tribe monitors the water quality and conducts physical habitat and bioassessments for the lake (http://www.plpt-waterquality.net/).

Water Rights
The Truckee-Carson-Pyramid Lake Water Rights Settlement Act of 1990 is an agreement to establish equitable apportionment of the Truckee River, Carson River, and Lake Tahoe waters between California and Nevada which include water rights for fish and wildlife, protection of wetlands, and enhancement and recovery of the Pyramid Lake fishery under the Endangered Species Act, and acquisition of Pyramid Lake Paiute Indian Water Rights. In 2009, the Truckee River Operating Agreement (TROA) was signed after several years of litigations and negotiations and it has reduced the water conflict among basin water users. The PLPT is one of the primary TROA stakeholders and is downstream of most users of the Truckee River. Their water rights are primarily for maintaining the ecosystem health of Pyramid Lake on which their livelihood and cultural values are based. Indian water rights in this basin are important not only for the socio-cultural and political reasons but also for ecological reasons in view of the need for the protection of endangered fish species such as the cui-ui (Parks and Stone, 2005).

Fishery Issues
In addition to the endangered cui-ui and threatened Lahontan cutthroat trout, Pyramid Lake supports populations of tui chub (Gila bicolor), Tahoe sucker (Catostomus tahoensis), and Sacramento perch (Archoplites interruptus) (http://www.pyramidlake.us/pyramidlake-fishing.html). Pyramid Lake is a terminal lake, meaning there is no surface outlet of water from the lake. Thus, the water quality of the lake is strongly tied to the quantity and quality of the Truckee River, the major surface water input to the lake, and the sustainability of the cui-ui and Lahontan cutthroat trout populations is therefore affected by the Truckee River and Pyramid Lake water quantity and quality dynamics. Diversions of the Truckee River led to declines in lake level and the formation of a shallow delta at the mouth of the Truckee River, which made it virtually impossible for the fish to migrate into the Truckee to spawn (Scoppettonne and Rissler 2007). Recovery efforts and the life history characteristics of the fish have enabled them to persist in the lake, but there are concerns about the continued viability of fish populations if lake levels and available fresh water from the Truckee River change under climate change.

The cui-ui are long-lived fish (40 years or more) that do not spawn every year. Sexual maturity begins at 8-15 years of age, and Scoppettone and Rissler (2000) found enhanced fecundity after a no-spawn year (usually due to low flows). They postulated that the fish may have adapted this life history strategy because of the natural occurrences of severe drought in the Great Basin (Scoppettone and Rissler 2000). In addition, the cui-ui spawn during the peak snowmelt from the Sierra Nevada, and Scoppettone et al. (1993) found that larvae survival was affected by water temperature. Best success occurred in cooler temperature regimes (8.9-15°C) and much lower survival occurred at warmer temperatures (17.8-23.9°C). They also noted that while cui-ui larvae did not do well at constant 23.3°C, cui-ui fish did seem able to tolerate temperatures up to 23.9°C when temperature fluctuated. (See Scoppettone and Rissler (2000, 2007).) Compared to the cui-ui, the Lahontan cutthroat trout are a relatively short-lived species and therefore did not survive the lowered lake levels and were extirpated from Pyramid Lake in the 1940s (Scoppettone and Rissler 2007). However, stocking programs have improved the trout fishery at Pyramid Lake. Several studies have been done regarding Lahontan cutthroat trout survival in alkaline waters (Wilkie et al. 1993, 1994; Wright et al. 1993), and Galat et al. (1985) studied the Lahontan cutthroat trout responses to different salinity and alkalinity environments.

To improve the ability of cui-ui and Lahontan cutthroat trout to migrate to their spawning habitats in the
Truckee River, the Pyramid Lake Fishway and the Marble Bluff Fish Handling Facility were constructed in 1976 (Formations 2008). These facilities are located at Marble Bluff Dam which is about 5.0 km upstream of Pyramid Lake on the Truckee River. If stream flows are high enough, the cui-ui often spawn in the stretch of the river between the lake and Marble Bluff Dam (Scoppettone and Rissler 2000). In addition to spawning and water quality issues, cui-ui, Lahontan cutthroat trout, and tui chub are often consumed by the American white pelican (Pelecanus erythorhynchos). The largest colony of this pelican in western North America is found on Anaho Island in Pyramid Lake (Murphy and Tracy 2005). Pelicans are opportunistic feeders, and will change locations for feeding as food availability changes. Pelicans will feed on fish in Pyramid Lake during the spawning season, but also feed in the shallow wetlands of Lahontan Valley and other areas within 100 miles of Pyramid Lake (Withers 2010).

The water surface elevation of Pyramid Lake is important to the success of the Pyramid Lake fish populations. If the lake water surface is high enough, fish can migrate more easily to the Truckee River for spawning. In addition, if water is deeper in the Truckee River delta, fish can arguably swim deeper to avoid pelican predation. The timing of the higher lake water surface is also important, because it needs to coincide with the spawning runs. Thus, an early spring snowmelt that occurs before diversions begin in mid-April tends to be better for Pyramid Lake fish because more of the water will make it to the lake, elevating lake levels and providing cooler water habitat in the Truckee River.

There are three hatcheries operated at Pyramid Lake that help to augment fish populations in the lake: the Numana Hatchery, the David Dunn Hachery, and the Dave Koch Cui-ui Hatchery. The largest hatchery at Pyramid Lake is the Numana Hatchery, which can produce up to 800,000 Lahontan cutthroat trout (Pyramid Lake Fisheries, 2008). The hatchery is located between Wadsworth and Nixon off of State Route 447. The Dunn Hatchery (http://pyramidlakefisheries.org/?page_id=8) is located in Sutcliffe, NV and was built from 1974-76. The only species raised at this hatchery is the Lahontan cutthroat trout. Operating since 1975, fish production is currently over one million fish annually. The Dave Koch Cui-ui Hatchery (http://pyramidlakefisheries.org/?page_id=7) is located in Sutcliffe behind the Dunn Hatchery. It has been producing fish since 1973. Production of hatchery fish provides protection against extinction by producing a viable year-class in drought years when low Truckee River flows cannot support "natural" spawning. The Dave Koch Hatchery includes both indoor and outdoor facilities. The indoor incubation facility at the Dave Koch Hatchery can incubate 2.3 million cui-ui eggs at one time. Newly-hatched larvae are reared in fiberglass troughs until they are able to swim, and then they are transferred to ponds so they can learn to feed on organisms naturally found in Pyramid Lake such as rotifers, ostracods, and other zooplankton, but are safe from predation. The fingerlings are planted into Pyramid Lake in the fall when they are about four inches long.

Adult cui-ui are kept in the outdoor hatchery facilities at Dave Koch until they are spawned. These facilities include circular fiberglass tanks and broodstock troughs. Cui-ui captured near the mouth of the Truckee River or at Marble Bluff Dam are brought to the hatchery in trucks. A carp-pituitary extract is used to speed the ripening process so the fish can spawn at the hatchery.

Climate change
Examination of trends in precipitation, temperature, and streamflows in the Sierra Nevada indicate that winter temperatures have increased, spring runoff has occurred earlier, and winter precipitation has stayed about the same or has increased over the past 50 years or so (Dettinger and Cayan 1995; Regonda et al. 2005; Cayan et al. 2008). Models run to simulate predicted impacts of climate change on these factors have generally shown continuations of these trends, with more winter precipitation occurring as rain rather than snow (Dettinger et al. 2004; Maurer 2007; Maurer et al. 2007).

Project Description
What are the impacts of climate change on the sustainability of the fish populations in Pyramid Lake? There are many diversions from the river system for municipal, mining, agricultural and industrial use. The fish populations to be considered can include Lahontan cutthroat trout, cui ui, and/or other fish. Lake levels can affect the vulnerability of fish to pelican predation. In addition, lake levels can affect hydrodynamics and water quality dynamics which can also affect fish populations. For example, water temperatures and dissolved oxygen affect fish survival and propagation.

Learning Goals or Outcomes

1. To create a system that is holistic and captures the various compartments of the ecosystem.
2. To think critically about the connection between each compartment and to link it to a model
3. To make an assessment of how climate change will impact the endangered fish.

How would you assess whether those goals have been met?

1. Creation of a model
2. Mathematical connection to model
3. Writing a report


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Websites that may be useful:

Fishery issues:

Pyramid Lake Paiute Tribe:

Pyramid Lake

Water quality:

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