Create-a-Fish: Crestone Sucker

THIS IS FICTIONAL. 

While I've based my creation on REAL field work by dedicated USGS and Trout Unlimited fisheries professionals and grounded it in realistic scientific sources, this work is just for FUN. 

ENJOY!

INTRODUCTION

The Crestone Sucker (Cryomallus cristomontis) is a fish uniquely adapted to the high alpine lakes of Colorado's Sangre de Cristo Mountains, where year-round, near-freezing temperatures and limited food resources define its habitat. These waters, too cold for Rio Grande Cutthroat Trout (Oncorhynchus clarkii virginalis) or introduced Brook Trout (Salvelinus fontinalis), have shaped Cryomallus into a cold-water specialist. 

DISCOVERY

In 2014, researchers began a project to eliminate nonnative cutthroat trout from the Sand Creek drainage within the Great Sand Dunes National Park. Andrew Todd and Ben McGee of the USGS, with Kevin Terry of Trout Unlimited set out to survey the Sand Creek Drainage. These dedicated researchers backpacked into the remote drainage, began an extensive electroshocking survey, and collected eDNA (McGee et al., 2019). As the team worked into the highest tributaries, they found the waters too cold for even Brook Trout or Rio Grande Cutthroat, but they wanted to be sure they had surveyed every inch. Brook Trout is a hardy fish and a cold water specialist. Any remaining populations would likely ruin the restoration work the team set out to accomplish. These surveys would be crucial for future rotenone applications. The research team had to get it right. 

They pressed into the highest tributaries, expecting to find nothing, yet to their surprise, they began to shock up some sucker individuals. Fred Bunch and Dewane Mosher from the NPS had extensive experience with these fish, so they shook their head when the radio relayed the news. There was no way sucker could be up that high. They are a valley-floor species. It was impossible. Bunch and Mosher would later, in 2023, be instrumental in future restoration work for Rio Grande Chub and Sucker (Livingston, 2023). However, a few more individuals showed up, but only in the highest reaches of the stream approaching an alpine lake. 

The research teams had primarily been working the mainstem of Sand Creek and had only begun to sample the headwaters, but they had yet to test any of the source lakes. These alpine lakes, surrounded by towering rocky cirques composed of Crestone conglomerate, held a surprise of a lifetime (Lindsey, 2010). It is a moment scientists dream of, but that dream would have to wait. Winter comes quickly in the high alpine, and the field season would not allow the team to survey the lakes. They had planned to perform bathymetric and fish surveys of the lakes in the 2015 field season (McGee et al., 2019).

As eDNA samples taken that summer began to roll in, there were traces of DNA from an unknown source. Each of these readings had been from high-altitude sample sites. It was beyond just an error. That is when the team knew they had to take a closer look at those sucker specimens. Individuals from that field season were rare, and as a native fish of Colorado, the sucker encounters were not a concern like Brook Trout, so the team did not inspect the fish closely even though it was a surprise. Winter could not pass quickly enough.

The 2015 field season opened when the snow melted enough to allow access into the basin in early June. This season, the team had pack rafts for the necessary bathymetric surveys of the lakes needing rotenone treatment. It was vital to know the lake measurements to administer the correct amount of piscicide (McGee et al., 2019). The lakes that had confirmed cutthroat hybrids and Brook Trout were the priority. However, the team felt a pull to take one of the rafts to the highest lakes in the system. Besides the stunning scenery of these high alpine lakes, they wanted to follow up on those eDNA anomalies. They wanted another look at those suckers they had released.

Bunch Creek Lake, at 11,344 ft, sits above Lower Sand Creek Lake. It is clear and dangerously cold. McGee inflated the pack raft for an afternoon paddle around the lake to take bathymetric measurements. Afternoon thunderheads built up in the distance. The team had been doing hook-and-line sampling at Lower Sand Creek Lake (McGee et al., 2019), so McGee had an ultralight fishing setup. They clipped Rio Grande Cutthroat fins at the lower lake for genetic analysis. The team desired to know the percentage of the fishery composed of hybrid cutthroat. He had not seen any fish but figured it was worth a try. He would likely have to retreat to camp due to the incoming storms. A small jig broke the surface and sunk to the bottom of the lake. McGee worked the jig slowly back to the raft when he was surprised to feel a tug. He set the hook and reeled the fish in. He noted that it put up little fight. It did not feel like a trout. 

With the fish in hand, he knew he had something unusual. This fish was not like anything he had seen. Its downturned mouth looked like the suckers from the valley floor, but the barbels were strange. In fact, the closer he looked, the more unfamiliar the fish became. Rough tubercles protruded from the forehead. Thunder rolled in the distance. It was time to get off the water. McGee took a picture, clipped a fin, and released the fish. He paddled to shore and rushed back to camp. He recalled ducking into the camp’s outfitter tent just as the sky cracked and the rain hit. Other team members rolled into camp as the storm pushed them off their surveys. McGee showed them the picture. Everyone agreed they needed to find more.

The next day, the team surveyed the highest lakes, each holding these mysterious fish. The team clipped the fins of each specimen and then preserved them for genetic analysis. The research team knew they had found something special but had to work hard to finish the cutthroat project. They completed their necessary surveys during the 2015 field season.

Fly fishermen tie flies to pass the short snowy days and long cold nights. Ichthyologists process samples. Snow blanketed the Flatirons above Boulder, Colorado when John Wood of Pisces Molecular received the fin samples the team had collected (McGee et al., 2019). Wood ran an analysis of the sucker fin clippings and compared it to the eDNA findings. They were a match. Wood called Ben McGee. He explained that he had found a match. He also told McGee that he had checked to see if the fin results had matched the Rio Grande Sucker. They had not, but there was a significant relationship between them. They shared a common ancestor at some point. It was not a subspecies. McGee had to confirm what Wood was implying. He asked if it was a new species. Wood agreed; that is what it seemed. They had discovered something special in those lakes. The following sections elaborate on the research that has followed their discovery. 

MORPHOLOGY AND PHYSICAL ADAPTATIONS

Cryomallus cristomontis exhibits counter-shading, an essential adaptation for blending into its high-altitude lake environment (Facey et al., 2023, p. 368). Its dorsal surface is dark grey, mirroring the granitic and gneiss substrate, while its ventral side is lighter grey. Due to guanine-lined scales, a silvery iridescence helps it remain inconspicuous from above and below (Facey et al., 2023, p. 369). This camouflage is particularly important in clear, oligotrophic waters with visual predators such as diving birds and otters. The species also features light yellow highlights on its fins, which may play a role in intraspecific recognition or seasonal breeding displays.

Cryomallus typically reaches a maximum length of 20 cm, a size possibly limited by its resource-poor environment. Future research is needed to establish the maximum size under ideal conditions. Its forked tail is optimized for efficient cruising through the water column while allowing rapid bursts of speed when evading predators (Facey et al., 2023, p. 65). Unlike more streamlined swimmers, Cryomallus has relatively wide and highly articulating pectoral and pelvic fins, enhancing maneuverability (Facey et al., 2023, p. 67). This adaptation is particularly beneficial for precise movements when foraging, as the species primarily sifts through lake sediment in search of small invertebrates.

Cryomallus has a well-developed lateral line system that detects subtle vibrations from conspecifics, prey, and predators (Facey et al., 2023, p. 98). Its small, dark eyes are adapted to the intense UV radiation found at high elevations, where thinner atmospheric layers provide little protection. The reduction in eye size minimizes potential UV damage while allowing sufficient light detection in its range's clear, unclouded waters (Facey et al., 2023, p. 107).

The scales of Cryomallus are fine and coated with a guanine mucus layer, reducing ion loss via diffusion. This guanine also imparts their silvery iridescence (Facey et al., 2023, p. 406). This is a crucial adaptation in the dilute freshwater environment, where maintaining osmotic balance is challenging due to the scarcity of mineral-rich inputs. Additionally, its kidneys are highly efficient and capable of conserving essential ions while excreting excess water, ensuring physiological stability in its low-nutrient habitat (Facey et al., 2023, p. 125).

Cryomallus has evolved specialized respiratory structures to maximize oxygen uptake. Despite cold water having high dissolved oxygen levels, the increased viscosity and slower diffusion rates present unique challenges. Cryomallus has slightly increased spacing between gill lamellae to counteract this, preventing them from sticking together under colder conditions. Its gill filaments are also more robust and designed to withstand dense water without collapsing. The species also boasts an extensive capillary network, improving oxygen delivery efficiency (Facey et al., 2023, p. 78). At the same time, an increased number of lamellae provides a greater surface area for gas exchange.  A specialized operculum structure protects the delicate gill filaments, shielding them from potential debris and damage. Furthermore, its efficient ability to buccal pump ensures a steady oxygen supply even when stationary, reducing energy expenditure (Facey et al., 2023, p. 78).

TAXONOMY AND EVOLUTIONARY HISTORY

Researchers in the field thought Cryomallus might be a subspecies of the Rio Grande Sucker (Catostomus plebeius) due to its proximate range, highly endemic nature, and morphology. However, genetic and molecular analysis revealed that Cryomallus is a distinct lineage adapted to extreme cold. It also showed that the two species share a common ancestor, so Cryomallus is phylogenetically placed similarly to the Rio Grande Sucker: Class: Actinopterygii; Order: Cypriniformes; Family: Catostomidae; Genus: Cryomallus; Species: C. cristomontis.

Cryomallus traces its lineage back to a shared ancestor with the Rio Grande Sucker, a species that has persisted in the valley streams of the Rio Grande Basin (Livingstone, 2023). Their evolutionary divergence is a story of shifting landscapes, climatic transformations, and the constraints of isolated mountain waters.

During the Pleistocene and early Holocene, the San Luis Valley was a vastly different environment than it is today. Unlike today’s arid, disconnected waterways, the valley floor was a mosaic of wetlands, lakes, and slow-moving rivers. Seasonal monsoons and glacial meltwater fed an extensive network of streams that provided connectivity between the mainstem Rio Grande, its tributaries, and higher-elevation lakes and streams (U.S. Geological Survey, 2007).

It was in this wetter, more interconnected world that the ancestral population of Cryomallus and the Rio Grande Sucker thrived. This fish likely exhibited generalist traits that allowed it to exploit the lowland floodplain habitats and streams. Some individuals migrated upstream to the headwater lakes to establish local populations. This subset of the ancestral population began to exploit the cold, oligotrophic waters of the upper tributaries and high alpine basins. Over millennia, these fish became increasingly specialized for life in extreme environments, facing a suite of evolutionary pressures that honed their adaptations. Transitioning to alpine lakes required physiological and behavioral modifications to withstand colder temperatures, lower nutrient availability, and increased isolation. Selection pressures favored individuals with greater cold tolerance, efficient energy metabolism, and enhanced reproductive strategies suited for short growing seasons. Two distinct lineages emerged,  the Rio Grande Sucker, which adapted to the perennial valley streams, where it retained its benthic feeding behaviors and tolerance for warmer waters, and Cryomallus, the high alpine specialist.

Despite their high-elevation refugia, connectivity between valley streams and alpine lakes persisted, allowing gene flow between Cryomallus populations. This connectivity, though sporadic as individuals rarely roam beyond their natal lake, helped maintain some genetic diversity and adaptive potential within the population.

The final nail in the coffin of connectivity came not from natural climatic shifts but from human intervention. The Closed Basin Project, implemented in the mid-20th century, drastically altered the hydrology of the northern San Luis Valley by diverting water away from the endorheic basin draining lakes, wetlands, and streams (Rio Grande Water Conservation District, n.d.). This large-scale water removal severed many links between the valley’s streams and the high mountain lakes, solidifying Cryomallus’ isolation.

HABITAT AND DISTRIBUTION

The Crestone Sucker (Cryomallus cristomontis) is a highly specialized fish endemic to the high alpine lakes of the Rio Grande drainage in the Sangre de Cristo Mountains of Colorado. These remote and isolated waters have shaped its evolution, allowing it to thrive in extreme conditions that exclude fish species. The significant drainages supporting high-quality habitat in headwater lakes include Medano Creek, Sand Creek, Cottonwood Creek, Willow Creek, Crestone Creek, and Wild Cherry Creek.

These lakes, situated at elevations exceeding 11,000 feet, remain largely untouched by human activity, partly due to their location in the Sangre de Cristo Wilderness Area or Great Sand Dunes National Park and Preserve. Their isolation has led to a lack of competition from more generalist species and prevented the introduction of predatory fish that could outcompete or prey on Cryomallus. The distribution of this species is tightly linked to cold, high-elevation aquatic ecosystems, making them highly vulnerable to environmental changes such as shifting precipitation patterns, increased evaporation, or temperature fluctuations caused by climate change.

The lakes inhabited by Cryomallus cristomontis share a distinct set of environmental characteristics that define their suitability for this species: they are oligotrophic, have high water clarity, and have cold year-round temperatures, rarely exceeding the upper 40s °F even in the peak of summer (McGee et al., 2019). These conditions are too extreme for species like the Rio Grande Cutthroat Trout (Oncorhynchus clarkii virginalis) or introduced Brook Trout (Salvelinus fontinalis), allowing Cryomallus to occupy an ecological niche free from significant fish competition or predation.

Unlike many fish species that exhibit habitat partitioning, Cryomallus cristomontis utilizes the entire lake due to the small size of these alpine systems (Facey et al., 2023, p. 508). It is commonly found at varying depths and across different lake substrates, ranging from rocky shallows to deeper benthic zones. This lack of strict habitat specialization is an adaptation to the spatial limitations of its environment, ensuring it can exploit all available resources (Facey et al., 2023, p. 517). The species is known to move through different sections of the water column depending on feeding conditions, predator presence, seasonal temperature changes, and dissolved oxygen levels.

Due to the harsh alpine environment and naturally fragmented habitat, Cryomallus cristomontis populations are highly localized and exhibit minimal genetic flow between lakes (Facey et al., 2023, p. 497). This geographic isolation has likely contributed to the species' unique physiological and behavioral adaptations, reinforcing its status as a cold-water specialist uniquely adapted to some of North America's most extreme freshwater habitats. 

FORAGING BEHAVIOR AND DIET

Cryomallus cristomontis is an omnivorous benthic feeder, combining scraping and suction-feeding to extract food from the substrate. Its downward-facing subterminal mouth is highly specialized for foraging. The species relies on sensitive barbels to detect and capture prey, allowing it to efficiently locate food sources buried in sediment (Facey et al., 2023, p. 111). These barbels serve multiple functions. The barbels have chemoreceptors that help Cryomallus locate prey by detecting dissolved organic compounds in the water. The barbels also assist in distinguishing between edible organic material and inorganic substrate as the fish sifts through sediment.

A distinctive feature is a specialized scraping ridge on its jaw, a feature shared with Rio Grande Sucker, Catostomus plebeius (George, 2023). This ridge effectively grazes on periphyton, algae, and detritus from submerged surfaces such as rocks, gravel, and boulders. This adaptation is crucial in the nutrient-poor alpine lakes. By scraping organic material from hard surfaces, Cryomallus maximizes its foraging efficiency and supplements its diet with a steady energy source (Facey et al., 2023, p. 526).

Its flexible and protrusible mouth structure also enables suction feeding, efficiently extracting small invertebrates from sediment substrates (Facey et al., 2023, p. 50). This dual feeding strategy, scraping and suction, makes Cryomallus a versatile forager that is well-adapted to its extreme environmental constraints.

During the spring and summer, Cryomallus takes advantage of increased invertebrate activity, feeding primarily on chironomid larvae and oligochaetes. They will feed on zooplankton and microcrustaceans, which are opportunistically consumed when drifting through the water column. As temperatures drop in the fall and winter, these food sources become scarcer, leading Cryomallus to rely more heavily on periphyton and detritus, scraping algae and organic matter from rocks and submerged structures.

Cryomallus is a generalist forager that utilizes the entire water column to maximize food intake (Facey et al., 2023, p. 517). Because the small, isolated alpine lakes it inhabits limit habitat specialization, Cryomallus takes advantage of all available feeding opportunities, foraging in lake bottom sediments, where it sifts through fine substrate for detritus and invertebrates, in shallow rocky zones where periphyton, algae, and detritus accumulate, in midwater zones used for opportunistic zooplankton consumption, and at the surface to consume any surface invertebrates. Cryomallus displays a unique “take” when surface feeding, as its ventral mouth means the fish has to flip over to feed, often leading to a splash or clumsy surface disturbance.

Foraging behavior is predominantly solitary, though individuals may aggregate in shallow areas during periods of high periphyton growth or peak invertebrate activity. Its highly maneuverable pectoral and pelvic fins allow precise foraging movements, ensuring efficient scraping and sifting without unnecessary energy expenditure.

LIFE CYCLE AND REPRODUCTION

Cryomallus cristomontis follows a slow but steady life cycle shaped by its alpine lake habitat's cold, oligotrophic waters. Like its close relative, the Rio Grande Sucker, it undergoes a multi-stage developmental process (George, 2023), with adaptations that allow it to survive in extreme conditions. Spawning occurs during the brief summer breeding season between late June and early August when water temperatures temporarily rise to levels suitable for reproduction, estimated between 2–7°C. Females deposit adhesive, demersal eggs onto rocky or gravelly substrates in shallow, well-oxygenated areas. To protect developing embryos from physical damage caused by ice, particles, and abrasion along the substrate, the chorion of the eggs is thick and robust (Facey et al., 2023, p. 138). The eggs also contain a rich lipid reserve, providing long-term energy for development in an environment where slow metabolic rates and limited external food sources make early survival challenging. The eggs produce antifreeze-like proteins to improve survival further, preventing lethal ice crystal formation within cells and surrounding fluids (Facey et al., 2023, p. 197). Due to the cold temperatures, embryos develop slowly, hatching for several weeks.

Newly hatched larvae remain close to the substrate, absorbing their remaining yolk sac reserves before transitioning to active foraging (Facey et al., 2023, p.154). Their early diet consists primarily of microorganisms, periphyton, and fine detritus, gradually shifting to benthic invertebrates as they grow (Facey et al., 2023, p. 155). Juveniles, which resemble miniature adults by their first year, develop the characteristic downward-facing mouth and scraping ridge that define their feeding strategy. Growth remains highly temperature-dependent, with individuals demonstrating faster growth in years of longer summers.

Sexual maturity is reached between three and four years of age, although this timeline can vary depending on growth rates and environmental conditions (Facey et al., 2023, p. 435). Once mature, individuals migrate to spawning areas in shallow, rocky zones of lakes or connected inflows during the short breeding season. Males and females are similar in size, but males exhibit distinct seasonal breeding characteristics. As the reproductive period approaches, males develop bright yellow highlights on their fins and small keratinized tubercles along their heads and pectoral fins (Facey et al., 2023, p. 393). These tubercles play a role in competitive displays and mating behaviors, with males engaging in brief but vigorous interactions to establish dominance and secure mates (Facey et al., 2023, p. 144). Once paired, the female releases her eggs over the substrate, and the male fertilizes them externally (Facey et al., 2023, p. 395). No parental care exists, and adults return to deeper waters after spawning (Facey et al., 2023, p. 397).

The extreme conditions of the environment shape Cryomallus's reproductive strategy. Instead of producing many offspring, this species relies on the resilience of its eggs and larvae to maintain stable but slow-growing populations. The combination of physiological adaptations, including antifreeze proteins, lipid-rich eggs, and a scraping-based foraging strategy, allows this species to persist in isolated alpine lakes, where its survival depends on long-term stability rather than rapid population expansion.

ECOLOGICAL ROLE AND NICHE

Cryomallus cristomontis occupies a unique position in the food web of its isolated alpine lakes, serving as both a primary consumer of benthic algae and detritus and a secondary consumer of small aquatic invertebrates. By grazing on periphyton and scraping organic material from rocks, it plays a critical role in regulating biofilm growth and nutrient cycling in the oligotrophic waters it inhabits. Additionally, preying on chironomid larvae, oligochaetes, and microcrustaceans influences the abundance of these benthic organisms, contributing to the overall stability of the lake’s invertebrate community. Its diet flexibility allows it to adapt to seasonal shifts in food availability, preventing population crashes in years when invertebrate numbers are low.

Cryomallus coexists with a limited number of competitors, as its habitat's cold temperatures and low productivity exclude many other fish species. The few potential competitors, such as introduced brook trout in some alpine lakes, tend to occupy different ecological niches. While trout primarily hunt for active invertebrates in the water column, Cryomallus specializes in benthic feeding, reducing direct competition (Facey et al., 2023, p. 509). Its interactions with other species are mainly dictated by food and habitat availability, with occasional overlap in feeding grounds during peak summer productivity. It also indirectly supports predator populations by serving as a food source for avian and mammalian species, linking primary production to higher trophic levels.

PREDATORS AND DEFENSE MECHANISMS

Cryomallus faces predation pressure from various high-altitude predators, particularly diving birds such as mergansers and herons, as well as semiaquatic mammals like river otters. These predators rely on the clarity of alpine lake waters to locate their prey, making Cryomallus particularly vulnerable in open-water environments. To counteract this, Cryomallus employs several avoidance strategies. Its counter-shaded coloration helps it blend into the lakebed, making it less conspicuous to aerial predators (Facey et al., 2023, p. 368). Additionally, its highly maneuverable pectoral and pelvic fins allow for rapid, precise movements when evading threats, while its forked tail provides short bursts of acceleration to escape pursuit (Facey et al., 2023, p. 65). Cryomallus also relies on its lateral line system to detect approaching predators, giving it an early warning system in the open water. During periods of high predation risk, individuals may seek cover among submerged rocks or deeper lake regions. However, the limited structural complexity of its environment means hiding places are scarce.

BEHAVIORAL TRAITS

The species exhibits a largely solitary lifestyle but may aggregate in shallow areas during peak foraging periods or spawning events. Unlike highly social schooling fish, Cryomallus moves independently or in loose, temporary groups, likely as a strategy to reduce competition in a resource-limited environment (Facey et al., 2023, p. 517). Seasonal changes in food availability and reproductive cycles dictate its movement patterns. Individuals may be more active in warmer months, covering greater distances within their small lake habitats in search of invertebrates and periphyton. During colder months, their movements slow considerably as metabolic rates decrease, conserving energy when food is scarce (Facey et al., 2023, p. 115).

HUMAN INTERACTIONS AND CULTURAL SIGNIFICANCE

While Cryomallus is not currently targeted for fishing, its presence in alpine lakes makes it an important indicator of ecosystem health. Studying its adaptations provides valuable insight into how fish can survive in extreme cold-water environments, informing conservation strategies for other high-altitude species. Additionally, its role in nutrient cycling and invertebrate population regulation highlights its ecological significance, even in lakes with low fish diversity. Though not widely recognized outside of scientific and conservation communities, Cryomallus could serve as a flagship species for alpine aquatic ecosystems, drawing attention to the impacts of climate change on high-elevation biodiversity.

CONCLUSION

Cryomallus cristomontis represents a remarkable example of adaptation to one of the most extreme freshwater environments. Its ability to survive near-freezing temperatures, subsist on limited food resources, and avoid predators in a structurally simple habitat demonstrates the resilience of fish in isolated alpine ecosystems. Cryomallus has carved out a niche in a habitat that excludes many other species through specialized feeding strategies, efficient metabolic regulation, and unique reproductive adaptations. However, with climate change increasing threat to high-altitude ecosystems, further research is needed to assess the species’ long-term viability and explore potential conservation measures. By studying Cryomallus and its environment, scientists can understand how freshwater fish adapt to extreme conditions and what steps may be necessary to protect these unique ecosystems in the face of a rapidly changing climate.

SOURCES

Berg, A. H., Westerlund, L., & Olsson, P. E. (2004). Regulation of Arctic char (Salvelinus alpinus) eggshell proteins and vitellogenin during reproduction and in response to 17β-estradiol and cortisol. General and Comparative Endocrinology, 135(3), 276–285. https://doi.org/10.1016/j.ygcen.2003.10.004 

Facey, D. E., Bowen, B. W., Collette, B. B., Helfman, G. S., & Bowen, B. W. (2023). The Diversity of fishes: Biology, evolution, and ecology (3rd ed.). John Wiley & Sons.

George, O., & Collins, S. F. (2023). Diet habits and trophic ecology of Rio Grande Sucker and Rio Grande Chub. Environmental Biology of Fishes, 106, 1669–1684. https://doi.org/10.1007/s10641-023-01443-9 

Gillet, C. (1991). Egg production in an Arctic charr (Salvelinus alpinus L.) broodstock: Effects of temperature on the timing of spawning and the quality of eggs. Aquatic Living Resources, 4(2), 109–116. https://doi.org/10.1051/alr:1991010 

Livingston, J. (2023, December 22). CPW, USFWS, and Great Sand Dunes partner to Expand Rio Grande chub and sucker populations. Colorado Parks and Wildlife. https://cpw.state.co.us/news/12222023/cpw-usfws-and-great-sand-dunes-partner-expand-rio-grande-chub-sucker-populations 

Lindsey, D. A. (2010). The geologic story of Colorado’s Sangre de Cristo Range (U.S. Geological Survey Circular 1349). U.S. Geological Survey. https://pubs.usgs.gov/circ/1349/pdf/C1349.pdf 

McGee, B., Todd, A., & Terry, K. (2019). Sand Creek characterization study for Oncorhynchus clarkii virginalis (Rio Grande Cutthroat Trout), Great Sand Dunes National Park and Preserve, Colorado (Scientific Investigations Report 2019–5061). U.S. Geological Survey. https://pubs.usgs.gov/sir/2019/5061/sir20195061.pdf 

Olk, T. R., Jeuthe, H., Thorarensen, H., Wollebæk, J., & Lydersen, E. (2020). Broodstock Management and early hatchery rearing of Arctic charr (Salvelinus alpinus [Linnaeus]). Reviews in Aquaculture, 12, 1595–1623. https://doi.org/10.1111/raq.12400 

Rinne, J. N. (1995). Reproductive biology of the Rio Grande Chub, Gila pandora (Teleostomi: Cypriniformes), in a montane stream, New Mexico. The Southwestern Naturalist, 40(1), 107–110. http://www.jstor.org/stable/30054402

Rio Grande Water Conservation District. (n.d.). Closed Basin Project. Rio Grande Water Conservation District. Retrieved March 12, 2025, from https://www.rgwcd.org/closed-basin-project 

U.S. Geological Survey. (2007). Hydrogeology of the San Luis Valley, Colorado (Open-File Report 2007-1193, Chapter G). U.S. Department of the Interior. https://pubs.usgs.gov/of/2007/1193/pdf/OF07-1193_ChG.pdf