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Cui-ui

The cui-ui (Chasmistes cujus) is a large, long-lived sucker fish endemic to Pyramid Lake and the lower Truckee River in northwestern Nevada, United States, representing the sole surviving species of a Pleistocene-era lake fauna that once included multiple endemic suckers.^[1] Characterized by a robust body reaching up to 66 cm in length, dark brownish coloration, and a lifespan exceeding 40 years, it primarily inhabits the lake's profundal waters, feeding on algae, detritus, and zooplankton while migrating upstream to spawn in spring.^[2] Listed as endangered under the U.S. Endangered Species Act since 1967 due to historical overfishing, habitat loss from upstream water diversions, and degraded spawning conditions in the Truckee River, the species has benefited from conservation measures including flow management, hatchery supplementation, and tribal stewardship by the Pyramid Lake Paiute Tribe, yet persistent recruitment variability and water quality issues maintain its critically imperiled status.^[3]^[4] Culturally significant to the Paiute people, for whom the lake is named "Cui-ui Standing Water," the fish's recovery trajectory underscores the interplay of hydrological alterations and restoration efforts in sustaining endemic lacustrine biodiversity.^[5]^[6]

Taxonomy and Description

Taxonomy

The cui-ui (Chasmistes cujus) is a species of ray-finned fish in the family Catostomidae, commonly known as suckers, which are characterized by their specialized ventral mouths adapted for benthic feeding.^[7]^[8] The species was formally described by American paleontologist and ichthyologist Edward Drinker Cope in 1883, based on specimens from Pyramid Lake, Nevada.^[6] Its full taxonomic hierarchy is as follows:

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Catostomidae
Genus: Chasmistes Jordan, 1878
Species: Chasmistes cujus Cope, 1883^[7]^[6]^[8]

The genus Chasmistes comprises three extant species endemic to western North American freshwater systems, with the cui-ui distinguished by its robust morphology and specialized lacustrine habitat; the other two species face similar conservation challenges due to habitat alteration.^[9] The etymology of the genus derives from Greek roots chanos (referring to the mouth) and istes (sailor or sucker), alluding to the family's suction-feeding apparatus, while the specific epithet cujus reflects the indigenous Northern Paiute name for the fish, pronounced similarly and denoting its cultural significance to local tribes.^[7] No significant taxonomic revisions or synonymies have altered its classification since Cope's description, as confirmed by integrated databases compiling peer-reviewed ichthyological records.^[8]

Physical Characteristics

The cui-ui (Chasmistes cujus) is a robust sucker fish with a long, broad, and deep head, a coarsely scaled body, and a slightly forked tail.^[10] It possesses a distinctive large terminal or ventro-terminal mouth that is oblique, adapted for feeding, with thin lips featuring obscurely papillose or separated lobes that may lack distinct papillae.^[10]^[11] Adults typically exhibit a dorsal coloration of blackish-brown with a bluish-gray cast, fading to creamy white on the belly, though some descriptions note a silvery overall appearance.^[10] During the breeding season, males develop tubercles on the anal and caudal fins.^[10] The species reaches a maximum total length of 67 cm and published weight of 2.7 kg, with females growing larger than males, exceeding 700 mm in length and up to 3.5 kg, while males attain about 662 mm.^[12]^[10] This sexual dimorphism in size reflects differences in growth rates and longevity, with individuals potentially living over 40 years.^[12]

Habitat and Distribution

Primary Habitat in Pyramid Lake

Pyramid Lake, located in northwestern Nevada on the Pyramid Lake Paiute Tribe Reservation, serves as the primary and sole remaining natural habitat for the cui-ui (Chasmistes cujus), a large endemic suckerfish. This terminal endorheic lake, a remnant of the Pleistocene Lake Lahontan, spans approximately 487 km² with a maximum depth of 111–119 m and lies at an elevation of about 1,158 m. As a monomictic water body, it stratifies thermally from May to December, with the thermocline typically at 11–23 m, and experiences high annual evaporation rates averaging 440,000 acre-feet, contributing to ongoing volume loss and concentrating dissolved solids.^[10]^[13] The lake's limnological conditions include saline waters exceeding 4.1 ppt salinity, alkaline pH of 9.1–9.3, and total dissolved solids (TDS) around 5,400 mg/L as measured in 1991, with levels having risen from approximately 3,500 mg/L historically due to upstream water diversions and evaporation. These parameters render the lake oligotrophic to mesotrophic, supporting planktonic food sources essential for cui-ui, though elevated TDS above 5,900 mg/L impairs egg hatching success to as low as 8% in lake water. Dissolved oxygen in the hypolimnion can deplete below 2 mg/L during summer, limiting deep-water usability and prompting cui-ui to favor shallower zones.^[10]^[1]^[10] Adult and juvenile cui-ui occupy the lake year-round for rearing, growth, and feeding, primarily inhabiting the inshore-benthic (littoral) zones and pelagic waters at depths less than 23–46 m, with concentrations often in 18–31 m depths and aggregations at the north and south ends during summer and fall. While some individuals venture to deeper benthic areas (75–100 m), seasonal anoxia risks constrain long-term residence there. The species demonstrates tolerance to the lake's high alkalinity and salinity, adaptations that distinguish it from less resilient fishes, but habitat quality is threatened by fluctuating lake levels, nutrient enrichment, and reduced Truckee River inflows, which exacerbate TDS accumulation and alter thermal regimes.^[10]^[1]^[11]

Spawning Migration in Truckee River

The cui-ui (Chasmistes cujus) is potamodromous, with adults migrating annually from Pyramid Lake into the lower Truckee River for spawning. This migration is obligate for reproduction, as the species requires stream conditions to deposit eggs successfully, though access is restricted to the lower 19 km of the river downstream of Derby Dam due to historical infrastructure barriers.^[14] ^[2] Upstream movement typically initiates in early April, coinciding with rising spring flows and water temperatures around 10–15°C, forming prespawning aggregations at the river mouth before ascending.^[6] Peak migration occurs in mid-May, with the run concluding by early to mid-June; however, low-flow years reduce the number of migrants, as insufficient discharge prevents effective navigation and limits spawning attempts.^[13] ^[6] Spawners generally travel less than 9.7 km upstream from the lake outlet, though accessible habitat now extends up to 13 km to Numana Dam in favorable conditions.^[2] ^[3] Spawning clusters form in shallow riffles with gravel substrates, primarily at night in depths of 9–43 cm and velocities supporting egg deposition; males defend territories over 4–5 days, while females spawn over 2.5–4 days in acts lasting 3–6 seconds, typically involving one female flanked by two males.^[15] ^[16] Post-spawning, adults return to Pyramid Lake, with juveniles descending the river later in summer after rearing in stream margins.^[15] Migration success has been hampered by flow regulation and channel incision since the early 20th century, reducing historical runs that once extended farther upstream.^[13]

Life History and Biology

Diet and Feeding Habits

The cui-ui (Chasmistes cujus) is primarily an invertivore, consuming zooplankton and benthic macroinvertebrates throughout its life stages.^[6] Larvae feed mainly on zooplankton and chironomid larvae.^[10] Juveniles ingest zooplankton such as cladocerans, copepods, and ostracods, along with chironomid larvae and algae.^[10] Adults predominantly consume zooplankton, including cladocerans and copepods, supplemented by chironomid larvae, ostracods, and other macroinvertebrates like Cyclops (a copepod genus).^[6]^[10] Feeding occurs in the littoral zone of Pyramid Lake at depths of 10–30 meters, with individuals foraging somewhat above the bottom substrate in both pelagic and benthic habitats.^[6] Juveniles are particularly active in summer and fall, targeting abundant planktonic prey, while adults exhibit similar but less specialized habits.^[10] These patterns reflect adaptations to the lake's oligotrophic conditions, where zooplankton abundance drives much of the trophic dynamics.^[6]

Reproduction and Spawning Behavior

The cui-ui (Chasmistes cujus) attains sexual maturity between 6 and 12 years of age, with initial spawning runs occurring at total lengths of 380–420 mm.^[1] Fecundity varies with female size, ranging from approximately 25,000 eggs in smaller individuals (around 430 mm) to over 186,000 eggs in larger females (up to 657 mm), with eggs measuring about 2 mm in diameter.^[10] ^[1] Due to the species' longevity exceeding 40 years, cui-ui exhibit reproductive longevity that allows for nonannual spawning patterns, enabling females to defer reproduction during years of poor hydrological conditions such as droughts that limit river access.^[17] ^[18] Spawning migrations commence in spring, with adults congregating near the Truckee River mouth at Pyramid Lake from mid-March to early June, peaking when high runoff provides suitable flows for upstream movement.^[1] The overall spawning period spans 4–8 weeks, though the majority of fish migrate during a concentrated 1–2 week interval, influenced by water temperatures of 14.4–17.2°C and minimum attraction flows of at least 60,000 acre-feet.^[2] ^[10] Primary spawning grounds are located in the lower Truckee River, extending up to 19.3 km upstream from Pyramid Lake, primarily over gravel substrates between barriers such as Marble Bluff Dam.^[10] Limited spawning also occurs at freshwater springs or interfaces within Pyramid Lake itself.^[10] During spawning, cui-ui form groups that ascend the river, where females broadcast demersal eggs over areas averaging 50 m², with individual spawning acts lasting 3–6 seconds and repeated more than 100 times per female.^[19] ^[20] Females typically spawn over 2.5–4 days, while males remain active for 4–5 days, with most activity concentrated at night in shallow riffles (depths of 9–43 cm, velocities supporting egg deposition).^[16] ^[19] Eggs settle into gravel interstices, where they may be partially covered by substrate movement, incubating in depths up to 10 cm under optimal intergravel dissolved oxygen levels above 5 mg/L.^[10] Sex ratios during runs favor females at approximately 1:1.3 to 1:2.^[1]

Growth, Longevity, and Population Dynamics

Cui-ui (Chasmistes cujus) display density-dependent growth patterns, with rapid length increases during the first 10 years of life, decelerating between ages 10 and 20, and ceasing thereafter.^[21] Growth rates are similar between sexes up to age 6, after which females outpace males, attaining lengths of 533–610 mm by age 13–14 for strong year classes like 1969, while males reach 458–546 mm.^[1] Sexual maturity typically begins at age 6 (380–420 mm length), though mean maturation age is 9.2 years for males and 9.6 years for females at low densities; higher densities delay this to 11.8 years for males and similar for females, reflecting resource competition.^[1]^[22] Longevity exceeds 40 years, with opercle bone validation confirming a maximum age of 41 years; reproductive lifespan supports persistence through intermittent spawning failures.^[1]^[3]^[17] Population dynamics are characterized by episodic recruitment tied to Truckee River flows for spawning migrations, with high adult survival (89% for males, 91% for females) sustaining cohorts during drought-induced reproductive failures.^[23] Prespawning aggregations numbered 103,000–187,000 adults in 1982–1983; post-1976 restoration via the Marble Bluff Fish Facility enabled a >10-fold increase to over 1 million adults, with estimates of 500,000–2 million since 1991 and spawning runs >200,000 in 2005, 2006, 2008, and 2010.^[1]^[22]^[3] Overall trends show stability or slight increases since the 1967 endangered listing, though recent data gaps necessitate updated surveys amid ongoing flow and climate pressures.^[3]

Historical Decline and Population Trends

Pre-20th Century Abundance

Prior to the 20th century, the cui-ui (Chasmistes cujus) maintained large populations in Pyramid Lake and adjacent Winnemucca Lake, supporting extensive spawning migrations up the Truckee River that drew communal harvests from the Pyramid Lake Paiute Tribe and neighboring bands.^[11] The species formed the cornerstone of Paiute subsistence, with the tribe earning the name "cui-ui eaters" (Kuyuidökadö) from other Northern Paiute groups due to their heavy reliance on the fish during spring runs.^[24] Archaeological records indicate sustained human occupation around Pyramid Lake for at least 11,000 years, enabled by the reliability and abundance of cui-ui as a protein source, supplemented by developed fishing technologies such as willow weirs, dip nets, and basket traps positioned at river confluences.^[11] These annual aggregations were substantial enough to attract intertribal gatherings, where groups like the Cui-ui Tikutta shared in the harvest, underscoring the fish's ecological productivity in the pre-diversion Truckee River system.^[10] Ethnographic accounts from the late 19th century describe runs so profuse that they facilitated drying and storage of fish for year-round use, with minimal evidence of overexploitation under traditional management practices that respected spawning cycles.^[25] While precise population estimates are unavailable due to the absence of quantitative surveys before modern fisheries science, the species' role as a dominant lacustrine planktivore in the Pleistocene remnants of Lake Lahontan implies naturally high densities sustained by nutrient-rich inflows and minimal anthropogenic pressures.^[3] This abundance persisted into the late 1800s, prior to upstream water diversions and habitat alterations that initiated declines.^[13]

20th Century Factors Leading to Decline

The population of the cui-ui (Chasmistes cujus) underwent a precipitous decline during the 20th century, driven chiefly by disruptions to its migratory spawning behavior and habitat integrity. The pivotal event was the completion of Derby Dam on the Truckee River in 1905, which facilitated the Newlands Reclamation Project's diversion of approximately 50% of the river's flow—averaging 250,000 acre-feet annually from 1918 to 1970—for irrigation purposes.^[10]^[13] This reduced inflows to Pyramid Lake, causing a sustained drop in lake elevation by about 25 meters between 1906 and 1982 and elevating salinity levels from roughly 3,500 mg/L to over 5,000 mg/L by the late century.^[1]^[10] The resultant entrenchment and erosion of the river channel formed a shallow, unstable delta at the lake's inlet by the 1930s, rendering it virtually impassable for upstream migrations essential to reproduction.^[13]^[1] These hydrological alterations directly impaired spawning success, as cui-ui require flowing gravel substrates in the Truckee River for egg deposition and incubation, with optimal conditions including velocities of 27–140 cm/s and depths of 21–110 cm.^[1] Low flows and delta barriers led to recurrent spawning failures from the 1930s, preventing larval emigration and recruitment; by the 1960s, the population comprised only three surviving year classes (from 1942, 1946, and 1950), signaling near-total reproductive collapse.^[10]^[1] Compounding this, diversions contributed to the desiccation of adjacent Winnemucca Lake by the 1930s amid drought and overuse, extirpating the cui-ui subpopulation there and confining the species solely to Pyramid Lake.^[10] Fishery records reflect the trajectory, with catches plummeting between 1956 and 1968, prompting the species' federal endangered listing in 1967.^[10] Subsidiary factors included habitat degradation from upstream activities such as channelization, livestock grazing, and timber harvesting, which increased sedimentation and riparian erosion, further degrading spawning sites.^[10] Commercial and tribal harvest, while exerting pressure on adult stocks—necessitating moratoriums in 1969, 1979, and 1984—did not constitute the root cause, as the absence of juvenile recruitment from failed spawning predominated, with pre-1950s cohorts dominating the biomass into the 1980s.^[10]^[1] By century's end, adult population estimates hovered around 100,000–300,000, a fraction of historical abundances, underscoring the causal primacy of water management over direct exploitation.^[10]^[1]

Conservation Status and Efforts

Listing and Legal Protections

The cui-ui (Chasmistes cujus) was federally listed as endangered under the U.S. Endangered Species Act (ESA) on March 11, 1967, making it one of the first species protected under precursors to the modern ESA framework.^[4] This designation stemmed from observed population declines due to habitat alterations and overfishing, triggering prohibitions on take, including harm or harassment, under Section 9 of the ESA, as well as Section 7 consultation requirements for federal actions potentially affecting the species or its critical habitat.^[2]^[9] The U.S. Fish and Wildlife Service (USFWS) designated Pyramid Lake and portions of the Truckee River as critical habitat for the cui-ui in 1983, affording additional safeguards against federal projects that could destroy or adversely modify essential spawning and rearing areas.^[10] Legal protections extend to cooperative management with the Pyramid Lake Paiute Tribe, which holds reserved water rights under the Winters Doctrine and operates under incidental take permits allowing limited subsistence harvest while prioritizing recovery.^[26] On the international level, the International Union for Conservation of Nature (IUCN) classifies the cui-ui as Endangered (EN) under criteria B1ac(ii,iv)+2ac(ii,iv), reflecting restricted range and ongoing habitat quality declines, with the assessment last updated in 2011.^[12] Complementary legislation, such as the Truckee-Carson-Pyramid Lake Water Rights Settlement Act of 1990, mandates minimum instream flows in the Truckee River to support cui-ui spawning migrations, enforced through federal-tribal agreements.^[27] These protections collectively aim to mitigate water diversions and barriers that historically imperiled the species, though enforcement relies on interagency coordination amid competing regional water demands.^[3]

Recovery Initiatives and Achievements

The Pyramid Lake Paiute Tribe (PLPT) initiated a cui-ui hatchery program in 1977 after techniques were developed by the U.S. Fish and Wildlife Service (USFWS) starting in 1973, producing an average of 7 million larvae annually from 1980 to 1984 for release into Pyramid Lake.^[3] This artificial propagation established a stable brood stock, meeting one criterion for potential delisting under the 1992 Cui-ui Recovery Plan.^[3] Construction of the Marble Bluff Fish Facility in 1976 provided a 4.8 km fishway enabling upstream migration for spawning, supporting natural reproduction alongside hatchery efforts.^[3] Population monitoring documented 16 year-classes by 2007, with 10 reaching reproductive age, and adult spawning runs exceeding 200,000 individuals in 2005, 2006, 2008, and 2010.^[3] Overall adult abundance stabilized at 500,000 to 2,000,000 since 1991, reflecting improved recruitment from combined propagation and habitat access.^[3] Recent infrastructure advancements include the Numana Dam Fish Passage Project, with groundbreaking on September 13, 2023, funded by $8.3 million from the Bipartisan Infrastructure Law in 2022, aimed at restoring 65 miles of Truckee River spawning habitat previously blocked for over a century.^[28] This PLPT-led initiative, in partnership with USFWS, is projected to enable passage for up to 600,000 cui-ui annually, enhancing genetic diversity and long-term viability.^[28] ^[29] Complementary actions, such as PLPT's invasive species prevention program launched in 2022 and successful water rights litigation securing inflows to Pyramid Lake, have further bolstered recovery by maintaining lake levels and water quality.^[30] ^[31] The Cui-ui Technical Workgroup continues to guide these efforts toward meeting remaining recovery plan objectives.^[3]

Ongoing Challenges in Recovery

Despite significant progress in restoring spawning access through facilities like the Marble Bluff Fish Passage completed in recent years, cui-ui recovery remains constrained by persistent water management issues, including insufficient annual inflows to Pyramid Lake, with a minimum of 45,000 acre-feet required to maintain suitable habitat conditions, yet implementation of the Truckee River Operating Agreement has stalled since 2008.^[3] Dams and diversions continue to alter Truckee River flows, exacerbating delta formation and river incision that limit accessible spawning habitat to approximately 13 kilometers downstream of Pyramid Lake.^[3]^[2] Climate change poses an additional threat by reducing snowpack and streamflows, shifting seasonal hydrographs and potentially diminishing the reliability of spawning cues tied to water temperatures of 9–17°C.^[3] Although adult population estimates have stabilized between 500,000 and 2,000,000 since 1991, the lack of updated monitoring— with the last comprehensive assessment in 2006—hampers evaluation of recruitment variability and long-term viability.^[3] Ongoing passage challenges at structures like Numana Dam further impede upstream migration, despite improvements, underscoring the need for revised recovery plans to address these hydrological dependencies.^[2]^[3] Legal and operational hurdles, including disputes over federal water rights enforcement, continue to affect habitat protection, as evidenced by Pyramid Lake Paiute Tribe litigation in 2023 alleging inadequate safeguarding of cui-ui spawning grounds.^[31] Sedimentation and siltation in river channels persist as barriers to effective migration, compounding anthropogenic flow alterations that have historically disrupted reproduction.^[2] These factors collectively illustrate that while delisting criteria from the 1992 Recovery Plan have not been fully met, targeted interventions in water allocation and monitoring are essential for sustained population stability.^[3]

Threats and Environmental Factors

Anthropogenic Impacts

The primary anthropogenic impacts on the cui-ui (Chasmistes cujus) stem from water diversions and dams constructed in the early 20th century, which drastically altered the hydrology of the Truckee River and Pyramid Lake. The completion of Derby Dam in 1905 initiated large-scale diversions for the Newlands Reclamation Project, averaging approximately 250,000 acre-feet per year between 1918 and 1970, reducing inflows to Pyramid Lake and causing the desiccation of adjacent Winnemucca Lake by the 1930s, thereby extirpating the cui-ui population there.^[10] These diversions lowered Pyramid Lake's water volume by about 30% and increased salinity from around 3,500 mg/L to over 5,000 mg/L by the late 20th century, while depositing sediments that formed an impassable delta at the river's mouth, blocking spawning migrations and resulting in an 18-year reproductive failure from 1950 to 1968.^[10] ^[3] Dams such as Marble Bluff Dam (built in 1976) and Numana Dam further constrained access to upstream spawning grounds, limiting migrations to roughly 13-20 km of the lower Truckee River despite fish ladders intended to facilitate passage.^[10] ^[3] Channelization, upstream impoundments like Stampede Reservoir, and ongoing water management for agricultural and municipal uses continue to disrupt natural flow regimes, exacerbating habitat degradation through reduced peak flows, increased erosion from grazing and timber activities, and gravel compaction from siltation.^[10] ^[3] Pollution from point and non-point sources, including municipal wastewater from Reno-Sparks, agricultural runoff, and industrial discharges, has degraded water quality in the Truckee River and Pyramid Lake, elevating total dissolved solids to levels around 5,400 mg/L and nutrient loads that promote periphyton growth, thereby reducing intergravel dissolved oxygen critical for egg incubation and survival.^[10] Contaminants such as endocrine disruptors and wildfire-induced nutrient pulses pose additional risks to larval development and overall population viability.^[3] Commercial and subsistence fishing exerted pressure during periods of low abundance, with catches declining sharply from 1956 to 1968, prompting the Pyramid Lake Paiute Tribe to impose harvest moratoriums in 1969, 1979, and 1984 to allow recovery amid habitat constraints.^[10] Urban expansion in the Truckee Meadows has intensified water demands and associated pollution, compounding these effects on the species' lacustrine-spawning life cycle.^[10]

Natural and Climatic Influences

The cui-ui (Chasmistes cujus) relies on seasonal high river flows in the Truckee River for successful upstream migration and spawning, which are highly sensitive to climatic variability in the arid Great Basin region. Insufficient spring runoff due to low precipitation or early snowmelt can result in inadequate water depths and velocities, preventing adults from accessing gravel substrates at sites like the Truckee River delta and Marble Bluff. For instance, severe droughts in years such as 1988–1991 and subsequent low-flow events have led to near-total spawning failures, with no significant recruitment observed when river discharges fall below critical thresholds of approximately 100 cubic feet per second.^[14] Water temperatures exceeding 13.9°C during spawning periods further impair egg viability and larval survival, a condition exacerbated by warmer ambient conditions linked to prolonged dry spells.^[32] Climate change projections indicate intensified threats through increased drought frequency and reduced snowpack in the Sierra Nevada, potentially decreasing annual inflows to Pyramid Lake by 10–20% or more under moderate warming scenarios, thereby elevating lake salinity and further stressing juvenile and adult cui-ui physiology.^[33] These shifts could disrupt the species' potamodromous life cycle, where larvae drift downstream to the lake for rearing, as altered hydrologic regimes shorten the window for downstream transport and increase stranding risks.^[34] Empirical data from fluctuating temperature experiments demonstrate that cui-ui eggs exposed to regimes mimicking drought-induced warming exhibit up to 50% higher mortality rates from fertilization to swim-up stage compared to stable cooler conditions.^[35] Among natural influences, predation by American white pelicans (Pelecanus erythrorhynchos) constitutes a primary source of adult mortality, particularly during post-spawning congregations near the Truckee River mouth where pelicans exploit dense aggregations.^[36] Over a 13-year monitoring period from 1991 to 2003, tagging and netting efforts estimated that pelican predation accounted for significant losses, with annual removals potentially exceeding 10% of the returning adult run in high-predation years, based on observed consumption rates and population censuses.^[37] While native piscivores like tui chub (Gila bicolor) may exert limited competitive pressure on planktonic feeding by juvenile cui-ui, no substantial evidence implicates disease or invasive competitors as dominant natural factors in recent population dynamics.^[1] These predation pressures interact with climatic stressors, as low lake levels concentrate fish in accessible foraging zones, amplifying vulnerability.^[38]

Cultural and Economic Significance

Importance to Indigenous Communities

The cui-ui (Chasmistes cujus) holds profound cultural and subsistence significance for the Pyramid Lake Paiute Tribe, a Northern Paiute community whose traditional name, Kuyuidökadö or "cui-ui eaters," reflects the fish's centrality to their identity and historical livelihood.^[24]^[39] Archaeological evidence indicates that indigenous peoples in the Lahontan Basin, including ancestors of the Paiute, relied on cui-ui as a major protein source for at least 11,000 years, with seasonal migrations of the fish drawing tribes from across the region for communal harvesting events that reinforced social bonds.^[11] Historically, the annual spawning runs of cui-ui in the Truckee River and Pyramid Lake were pivotal events, providing abundant food that supported large gatherings not only of the Pyramid Lake Paiute but also distant Paiute groups, sustaining populations through arid conditions where other resources were scarce.^[40] The fish's fat content and ease of preservation through drying made it a staple, integral to ceremonies, trade, and survival strategies adapted to the desert environment.^[41] In contemporary times, the Pyramid Lake Paiute Tribe continues limited subsistence harvesting of cui-ui under federal regulations, viewing it as a living link to ancestral practices amid ongoing conservation efforts.^[26] The species' endangered status underscores its role as a primary cultural resource, with tribal initiatives prioritizing its recovery to preserve sovereignty over traditional foods and ecological knowledge.^[42]^[13]

Broader Historical and Subsistence Role

In the late 19th century, non-Paiute commercial fishermen, primarily Euro-American settlers, began exploiting Pyramid Lake's fisheries, including the cui-ui, leading to conflicts with the Pyramid Lake Paiute Tribe. During the 1870s, white fishermen trespassed onto the Pyramid Lake Reservation, employing boats and large nets to harvest fish stocks, which encompassed cui-ui alongside species like the Lahontan cutthroat trout. This activity contributed to early overexploitation, as annual rail shipments of fish from nearby stations such as Wadsworth and Verdi averaged over 100,000 pounds between 1873 and 1922, with cui-ui forming part of the catch sent to urban markets.^[43] By the early 20th century, commercial fishing persisted, shifting to include Asian immigrant laborers who targeted cui-ui and other lake species after many white operators exited the industry due to declining stocks and logistical challenges. Paiute tribal members occasionally participated by selling fishing permits to outsiders and serving as guides, integrating non-tribal harvesters into the local economy, though this practice heightened tribal concerns over resource depletion. Market-driven harvesting, rather than subsistence needs, characterized this era's broader role for cui-ui, as fish were sold for profit amid Nevada's growing rail networks facilitating export to distant consumers.^[43]^[44] Subsistence use by non-indigenous groups remained secondary to commercial efforts, with limited records of settlers relying on cui-ui as a staple food source outside recreational or opportunistic catches. In the mid-20th century, state regulations under the Nevada Fish and Game Commission's 1955 management plan permitted non-Indian anglers a daily limit of five cui-ui, treating it as a game fish comparable to trout, though populations had already dwindled to the point where it no longer supported viable non-tribal subsistence by the 1930s. This regulatory framework reflected cui-ui's diminished broader utility, overshadowed by its cultural primacy for the Paiute and the ecological fallout from upstream diversions and overharvest.^[43]^[45]

References

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[PDF] Life History and Status of the Endangered Cui-ui of Pyramid Lake ...
cui-ui (Chasmistes cujus) is a federally listed endangered species endemic to Pyramid Lake, Nevada. The species is believed to be the last remaining ...
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Sep 4, 2024 · Poor fish passage conditions have prevailed for half of the 20th century and are a significant factor of near extinction and 1967 listing of cui ...
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[PDF] 5-YEAR REVIEW Cui-ui (Chasmistes cujus) - AWS
Aug 31, 2023 · The following threats to Cui-ui were identified as justifications for federally listing as endangered in 1967 under the Endangered Species ...
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Cui-ui (Chasmistes cujus) | U.S. Fish & Wildlife Service
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S3: E46 Cui-ui.pdf | FWS.gov - U.S. Fish and Wildlife Service
Meet a beautiful, long-lived sucker found nowhere else on Earth except Nevada's Pyramid Lake (known also as Kooyooe Pa'a Panunadu/"Cui-ui Standing Water" by the ...Missing: facts | Show results with:facts
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Chasmistes cujus - NatureServe Explorer
Cui-ui - Natureserve Global Rank: G1: Occurs only in Pyramid Lake and Truckee River, Nevada; major problem is reduced flow and water quality of the Truckee ...
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Chasmistes cujus, Cui-ui : fisheries, gamefish - FishBase
Classification / Names Common names | Synonyms | Catalog of Fishes(genus, species) | ITIS | CoL | WoRMS | Cloffa. Etymology: Chasmistes: Greek, chanos, -eos, ...
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Endangered cui-ui of Pyramid Lake, Nevada - USGS.gov
Cui-ui is one of three remaining species of the genus Chasmistes. Of the three, its habitat is most intact, and it thus has the best opportunity for recovery ( ...Missing: family | Show results with:family<|control11|><|separator|>
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[PDF] GUI-UI RECOVERY PLAN - ECOS
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"Life history of the cui-ui, <i>Chasmistes cujus</i> Cope, in Pyramid ...
Cui-ui, endangered, reproduce in hatcheries and naturally. They grow slowly, may live 18+ years, and eat algae and zooplankton. They are vulnerable during ...
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Chasmistes cujus, Cui-ui : fisheries, gamefish - FishBase
Occurs in deep water. Spawns only around margin of Pyramid Lake in Nevada, USA but formerly made spectacular spawning runs up Truckee River in Nevada, USA.Missing: family | Show results with:family
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[PDF] Habitat Quality and Recruitment Success of Cui-ui in the Truckee ...
Pyramid Lake is approximately 487 km2 and lies within the boundary of the Pyramid. Lake Reservation in west-central Nevada, at the western edge of the Lahontan ...Missing: temperature | Show results with:temperature
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The cui-ui (Chasmistes cujus) is a large sucker fish endemic to Pyramid Lake ... Conservation status. Endangered (IUCN 3.1). CITES Appendix I (CITES).Missing: habitat | Show results with:habitat
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Cui-ui - Center for Biological Diversity
Because similar conditions are not likely to occur reliably enough to assure recovery, the cui-ui retains its' endangered status [4].
[16]
Reproduction by the endangered cui-ui in the lower Truckee River
Males spawned over a 4–5-day period, and females over 2.5–4 days. Most spawning occurred at night in water depths ranging from 9 to 43 cm, water velocities ...
[17]
Reproduction by the endangered cui-ui in the lower Truckee River
Cui-uis spawned in clusters of two to seven fish; usually a single female was flanked by two males. Each spawning act lasted 3–6 seconds, and individual fish ...Missing: facts | Show results with:facts
[18]
Reproductive longevity and fecundity associated with nonannual ...
The cui-ui Chasmistes cujus, a long-lived (40 years or more) and highly fecund catostomid, is often prevented from spawning in drought years.
[19]
Reproductive Longevity and Fecundity Associated with Nonannual ...
The cui‐ui Chasmistes cujus, a long‐lived (40 years or more) and highly fecund catostomid, is often prevented from spawning in drought years. We studied the ...
[20]
Reproduction by the Endangered Cui-ui in the Lower Truckee River
Individual females broadcast eggs over an area of up to 50 m2. Males spawned over a 4–5-day period, and females over 2.5–4 days. Most spawning occurred at night ...
[21]
Cui-ui | Encyclopedia.com
The cui-ui, Chasmistes cujus, is a is a plump, robust sucker, which attains a maximum length of about 25 in (64 cm) and a maximum weight of about 7 lbs (3.2 kg) ...Missing: size | Show results with:size
[22]
Growth and longevity of the cui-ui and longevity of other catostomids ...
Growth was rapid during the first 10 years, slow from 10 to 20 years, and extremely slow or nil after 20 years. Age and growth were strongly correlated for ...
[23]
Effects of population increase on cui-ui growth and maturation
Cui-ui Chasmistes cujus is endemic to Pyramid Lake, Nevada. The cui-ui population declined during much of the 20th century as a result of water diversion ...
[24]
Population Dynamics of the Cui-ui of Pyramid Lake, Nevada
Adult Cui-ui survival averaged 91% and 89% for females and males, respectively, in drought years when spawning migrations were either precluded or few fish ...
[25]
8. The People of Pyramid Lake - National Park Service
Jul 3, 2017 · Native people called the Cui-ui eaters (or the Paiute) lived in the area surrounding the lake. These people were fishermen who caught and ate the Cui-ui fish ...
[26]
[PDF] An Environmental History of Northern Nevada's Pyramid Lake and ...
Mar 21, 2013 · Commission also agreed to let sportsmen harvest the cui-ui only after the Paiutes had met their needs. 49. The Paiutes feared that the cui-ui ...
[27]
[PDF] Cui-ui with Erik Horgen 11/13/23 - U.S. Fish and Wildlife Service
And it got worse and worse as it migrated up the. Truckee River that was a natural fish migration berrier. 09:05. Oh, man. Okay. 09:06. It was about 40 feet ...
[28]
Truckee-Carson-Pyramid Lake Water Rights Settlement Act 101st ...
Directs the Secretary of the Army to develop facilities to enable the passage of cui-ui and Lahontan cutthroat trout through or around the delta at the mouth of ...
[29]
Numana Dam Fish Passage Project | U.S. Fish & Wildlife Service
Sep 20, 2023 · Decades of recovery efforts have been made possible by a longstanding partnership between the Pyramid Lake Paiute Tribe, the U.S. Fish and ...
[30]
Pyramid Lake Paiute Tribe efforts to recover endangered Cui-ui
Oct 5, 2023 · The Pyramid Lake Paiute Tribe is excited to finally see shovels break ground on a decades-long effort to recover their native fish.
[31]
Tribe works to keep home of endangered fish free of invasive species
Jan 3, 2022 · The Pyramid Lake Tribe's aquatic invasive species program is a new effort designed to preserve the federally endangered and threatened fish species in the lake.
[32]
NV tribe sues feds over water rights, failure to protect endangered fish
Jul 25, 2023 · After a long struggle and numerous court actions, the Pyramid Lake Paiute Tribe was able to use the Endangered Species Act as a powerful legal ...Missing: USFWS | Show results with:USFWS
[33]
LIFE HISTORY OF THE CUI-UI, CHASMISTES CUJUS COPE ... - jstor
Abstract - The cui-ui, Chasmistes cujus Cope, a member of the sucker family and endemic to Pyramid Lake,. Nevada, is listed as endangered by the U.S. Fish ...
[34]
The case of the Pyramid Lake Paiute Tribe | Climatic Change
Apr 9, 2013 · Climatic and non-climatic impacts threaten the endangered cui-ui fish by decreasing water quantity and quality. However, an integrated ...
[35]
Water availability drives instream conditions and life-history of an ...
Aug 1, 2022 · ... Chasmistes cujus, a species endemic to Pyramid Lake and the Truckee River listed as Endangered under the ESA. Today, all fish must enter the ...
[36]
Impact of climate change on endangered fish population in Pyramid ...
Nov 23, 2010 · In addition to spawning and water quality issues, cui-ui, Lahontan cutthroat trout, and tui chub are often consumed by the American white ...
[37]
American white pelican predation on Cui-ui in Pyramid Lake, Nevada
Jan 24, 2014 · Anthropogenic changes to the Pyramid Lake–Truckee River ecosystem in Nevada are suspected to have altered the predator–prey balance between ...
[38]
Endangered cui-ui of Pyramid Lake, Nevada
Cui-ui (Chasmistes cujus) is a large plankton-feeding fish that only occurs in Pyramid Lake, Nevada. It was put on the federal endangered list in 1967 based ...
[39]
American White Pelican Predation on Cui-ui in Pyramid Lake, Nevada
Aug 7, 2025 · We estimated the loss of the adult Cui‐ui population to pelican predation over a 13‐year period by netting and tagging Cui‐uis as they ...
[40]
Fishing | Pyramid Lake Nevada
The cui-ui once flourished in Pyramid Lake where it was one of the main foods of the Paiute people (who call themselves Cuyui Ticutta (check on that), ...
[41]
Cui-ui - Truckee River Guide
Cui-ui. Chasmistes cujus. Males are black or brown above and white below. During breeding season (April to June), red or brassy colored on sides.Missing: morphology | Show results with:morphology
[42]
[PDF] Arid Lands of the Southwest - USGS.gov
Aug 11, 2005 · It reaches lengths in excess of 30 inches and weights up to 10 pounds. Cui-ui are a favorite food fish of the Northern Paiute Indians and have ...Missing: size | Show results with:size
[43]
[PDF] Unique Challenges Facing Southwestern Tribes
It is home to an endangered fish called cui-ui (Chasmistes cujus)—a primary cultural resource—and the threatened Lahontan cutthroat trout. The Paiute tribe's ...
[44]
https://www.newyorker.com/magazine/1955/01/01/the-lake-of-the-cui-ui-eaters
[45]
The Lake of the Cui-Ui Eaters—I | The New Yorker
The Lake of the Cui-Ui Eaters—I” by A. J. ... Pyramid Lake ... (The Paiutes in those days sold fishing permits to outsiders and hired out as guides.) ...
[46]
PYRAMID LAKE : Large Lahontan Cutthroat Trout Make a Comeback
May 24, 1986 · Heavy turn-of-the-century market fishing and the introduction ... The Cui-ui, which is on the federal endangered species list, can be ...