Bear River Cutthroat

Oncorhynchus virginalis ssp.

Native Trout Fly Fishing

A Bear River Cutthroat from a beaver pond in Wyoming.

Introduction

The Bear River Cutthroat are native to the Bear River watershed in the Bonneville basin of Idaho, Utah and Wyoming. While it has long been recognized that the Bear River Cutthroat were unique among Bonneville Cutthroat, the two forms of Cutthroat were lumped together as a single subspecies until recently (Behnke 1992, Behnke 2002). Genetics work has shown that Bear River Cutthroat are more closely related to the Yellowstone Cutthroat than they are the Bonneville Cutthroat that inhabit the rest of the basin (Campbell et al. 2007, Campbell et al. 2011, Campbell et al. 2018). Geologic evidence indicates that the Bear River was a tributary to the Snake River until about 500,000 years ago when volcanic activity diverted the river south into its own internal basin forming ancient Lake Thatcher (Bouchard et al. 1998). The connection to the Bonneville Basin is believed to be much more recent and likely occurred about 20,000 years ago when Lake Thatcher overflowed into the Bonneville Basin and ancient Lake Bonneville (Link et al. 1999). Since that time the Bear River has flowed into the Bonneville Basin. Interestingly, the trout of the upper Malad River, which drains to the Bear River, appear to be Bonneville Cutthroat instead of Bear River Cutthroat, which may represent populations from when the Malad River was a direct tributary to Lake Bonneville or isolated as Lake Bonneville receded (Eaton et al. 2018). Additionally, there appears to be a zone of contact between Bear River and Bonneville Cutthroat in the Weber River watershed in Utah, where an intermediate form between the two subspecies occurs (Houston et al. 2013). Based on the genetic evidence indicating that they are distinct from Bonneville Cutthroat, the Bear River Cutthroat are proposed to be recognized as a distinct subspecies (Trotter et al. 2018).

Life History Information

Bear River Cutthroat exhibit three life history strategies, stream resident, fluvial (river migrant) and adfluvial (stream to lake migrant). Like all Cutthroat Trout, Bear River Cutthroat spawn in the spring and capable of spawning multiple times (iteroparous).

Stream Resident Life History

Stream resident populations of Bear River Cutthroat are found in many of the tributary streams throughout their native range. These stream resident populations are often isolated above barriers, but in some cases co-occur with fluvial or adfluvial populations. For example, Hilderbrand and Kershner (2000) found that 61% of Cutthroat in a tributary to the Logan River were resident and 39% were fluvial. In Bear Lake tributaries, stream resident populations in the upper reaches of the streams and utilize different habitat for spawning and rearing than the adfluvial fish do. With parts of the Bear River drainage flowing through arid sage-steppe grassland habitat, Bear River Cutthroat are noted for being able to withstand relatively high water-temperatures. Jonstone and Rahel (2003) showed that Bear River Cutthroat can survive daily water temperatures swings ranging from of 61° F to 79° F (16° to 26° C), however they also found that chronic exposure to temperatures over 77° F (25° C) are lethal to Bear River Cutthroat.

Stream resident Bear River Cutthroat are opportunistic feeders, preying on what is available. For example, fish in beaver ponds tend to feed primarily on midges, while fish in flowing segments of streams feed on a mix of aquatic and terrestrial invertebrates, with caddisflies and terrestrial invertebrates accounting for most of their diet (Hilderbrand and Kershner 2004). In general resident Bear River Cutthroat reach a maximum size of 13” (32 cm) by age 4, although larger fish may be found in more fertile streams (Binns 1981). Stream resident Cutthroat in the basin typically reach sexual maturity by age-3, with some males maturing at age-2. Although spawn timing varies depending on altitude and water temperatures, most stream resident fish spawn from April to July (Keshner 1995). Most females spawning for the first time are between 5” to 8” (12 to 25 cm) and have an average fecundity of 165 eggs (Binns 1981). Stream resident Cutthroat in tributaries to Bear Lake, typically spawn in higher gradient reaches using small pockets of gravel in riffles and pools, a pattern also seen in some Wyoming populations (Kershner 1995). While stream resident fish have small home ranges, resident Cutthroat in a tributary to the Logan River made small migrations that averaged 1,893’ (577 m) to spawn in the spring (Hilderbrand and Kershner 2000). However, during summer these fish moved very little and had average home ranges of just 180’ (55 m).

Fluvial (River Migratory) Life History

Despite significant declines, Bear River Cutthroat have managed to maintain a fluvial life history strategy across parts their native range. Unlike stream resident fish, which have small home ranges, fluvial fish are highly mobile, a strategy that typically allows fluvial Cutthroat to reach larger sizes than stream resident fish. A study on fluvial fish in a tributary to the Bear River showed that they had an average size of ~16” (420 cm), although some fish reached sizes of up to 22” (57 cm) (Sepulveda et al. 2009). The primary prey items of fluvial Bear River Cutthroat appear to be aquatic and terrestrial invertebrates, with larger individuals also preying on forage fish. Fleener (1952) showed that Cutthroat in the Logan River primarily fed on mayflies, caddisflies, midges and beetles during the summer months, but also ate fish eggs and forage fish when available.

Although the stream resident life history appears to be dominant in many streams, around 40% of fish appear to express the fluvial life history. For example, Hilderbrand and Kershner (2000) found that 39% of Cutthroat in tributaries to the Logan River exhibit a fluvial life history, while Randall (2012) estimated 41% to be fluvial. Strategies for fluvial fish appear to be variable, with some fluvial Bear River Cutthroat rearing in tributaries for one year until they reach a size of 3.5” to 4.7” (9 cm to 12 cm) before migrating to mainstem habitat to forage (Colyer and Harig 2004). Other fluvial fish migrate downstream into mainstem habitat as fry in early fall, corresponding with declining flows that limit their preferred shallow stream margin habitat in the tributaries (Bernard and Israelsen 1982). In tributaries to the Logan River, a fluvial strategy appears to result in a higher growth rate for smaller fish, but resulted in somewhat slower growth in larger fish, resulting in some individuals transitioning back to a stream resident strategy at around 10” (25 cm) (Randall 2012). Many fluvial Bear River Cutthroat spend the summer foraging in their natal spawning tributaries alongside stream resident fish and appear to display strong homing back to within ~ 330’ (100 m) of their summer rearing territory (Randall 2012). Summer home ranges for fluvial fish are variable in size, but some fish have been observed to range up to a mile (1.6 km) (Schrank and Rahel 2004, Colyer et al. 2005). The importance of tributaries for summer rearing habitat is likely linked to a lack of suitable summer habitat in some mainstem rivers. For example, in the mainstem Bear River downstream of the outlet of Bear Lake, summer water temperatures can exceed the lethal limit of 75.6° F (24.2° C) for Bear River Cutthroat and other parts of the mainstem regularly exceed 71.6° F (22° C), resulting in high stress and poor growth for Cutthroat (Johnstone and Rahel 2003, Hillyard and Keeley 2009). As such, Cutthroat that remain in mainstem habitat during the summer often seek out cold water refugia, which is typically found in areas associated with springs or stream mouths (Hillyard and Keeley 2012).

As summer comes to an end, fluvial Cutthroat move out of their tributary rearing habitat and back into mainstem habitat find suitable overwintering areas. Throughout the winter months, these Cutthroat appear to be very sedentary and are often observed overwintering in beaver ponds, which are an important habitat for these fish (Carlson and Rahel 2010, Randall 2012). These Cutthroat typically remain in their overwintering habitat until the onset of spring runoff, when they begin their spawning migrations (Randall 2012). Some of these spawning migrations can be quite extensive, and the average fish in the Thomas Fork River travels 23 miles (37.1 km) to reach their spawning grounds, with some traveling over 50 miles (86 km) (Schrank and Rahel 2004, Colyer et al. 2005). Cutthroat in the Logan River, of Utah and Idaho typically spawn between late April and mid-July during the onset of spring runoff and as it is subsiding (Bernard and Israelsen 1982, Bennett et al. 2012). Budy et al. (2012) found that 70% of Cutthroat redds were constructed as spring run-off subsided and when water temperatures ranged from 38°F to 62°F (3.1°C to 16.7°C). Spawning locations of Cutthroat are often associated with beaver ponds, with Cutthroat often using newly opened habitat after dams failed or areas in the inflow or outflows of the beaver ponds (Bennett et al. 2012). In the Logan River watershed, in addition to utilizing larger headwater tributaries, many fluvial Cutthroat depend on smaller streams including some that become intermittent in late summer and fall for spawning and early rearing (Cowley 2000). Mortality rates appear to be high after spawning and Cutthroat in the Smith Fork Bear River experience a seasonal mortality rate of 43% (Carlson and Rahel 2010). Of the Cutthroat that survive spawning, some migrate back downstream into mainstem habitat, but many remain in their spawning streams to forage over the summer. Eggs generally develop rapidly and hatch in July, with juveniles emerging from the gravel between late-July and early August (Budy et al. 2012).

Adfluvial (Stream to Lake Migratory) Life History

Adfluvial populations of Bear River Cutthroat native to two relatively large lakes across their range, Bear Lake in Utah and Idaho and Lake Alice in Wyoming. In addition to these lakes, they have also been introduced to several other lakes and reservoirs, such as Strawberry Reservoir in Utah. Of their two native lakes, Lake Alice is by far the smallest at 3 miles (4.8 km) long and with a surface area of 230 acres. The lake was formed when a landslide dammed its outlet, Porter Creek, which now flows subsurface through the slide area, effectively and isolating the previously stream resident and fluvial population of Cutthroat upstream. As the Cutthroat in Alice Lake derived from a stream resident and fluvial population, they show similar characteristics to other stream resident of fluvial populations. For example, despite the presence of native sculpin in the lake, Lake Alice Cutthroat primarily feed on aquatic and terrestrial invertebrates and only reach a maximum size of approximately 14” (35.6 cm) and with an apparent maximum age of 4 (Binns 1981, Trotter 2008). Lake Alice Cutthroat typically spawn from late-May to mid-June in the lake’s inlet stream and females have an average fecundity of 474 eggs (Binns 1981).

Unlike Lake Alice, Bear Lake, is large waterbody at 19 miles (30.6 km) long and with a surface area of 109 square miles (280 square km). Bear Lake Cutthroat Trout evolved as the apex predator in the lake’s a complex food web which includes six native species such as the Bear Lake sculpin, the Utah Sucker, and Bonneville and Bear Lake Whitefish and Bonneville Cisco (Snyder 1919). Once Bear Lake Cutthroat reach a size of 9” (22.5 cm), they become predominantly piscivorous, with the Bear Lake Sculpin and Bear Lake Cisco being the preferred prey item (Kershner 1995). The lake is not particularly fertile and as a result, Bear Lake Cutthroat are known to be particularly long lived with a maximum age of 14 years. Despite the nutrient poor waters, their long lifespan and reliance on fish in their diet resulted in Bear Lake Cutthroat being able attain weights of up to 25lbs. (11.3 kg) (Trotter 2008).

While some Bear Lake Cutthroat may spawn as early as age-3, most don’t spawn until age-6 (~70% of females), with some not spawning for the first time until the age-11 (Nielsen and Lentsch 1988, Nielsen and Birdsey 1991, Trotter 2008, Heller 2022a). Bear Lake Cutthroat was historically disconnected from the Bear River and its Cutthroat adapted to spawning in the tributaries to the lake. Spawning fish typically begin entering tributaries in April and peak in late May or early June, during the period of highest runoff (Nielsen and Birdsey 1991). Shortly after entering the tributaries the Cutthroat search out pool tailouts with relatively fine cobble in the lower portions of the creeks and spawn from late-April through mid-June (Kershner 1995). Spawners typically average 21” to 24” (53 cm to 60 cm) at 4lb to 5lb (1.8 kg to 2.3kg) and have an estimated average fecundity of 2,989 eggs per female (Trotter 2008, Heller et al. 2022a). Post spawning mortality rates appear to be high as is indicated in the number of repeat spawners, which typically average less than 3% of the run, but may account for up to 7% of the run (Nielsen and Birdsey 1991). Fish that do survive are thought to migrate back to the lake shortly after spawning.

Adfluvial Cutthroat fry typically emerge from the gravel at night, from mid to late summer and initially utilize stream margin habitat, with some out-migrating directly to the lake as young-of-the-year fish (Kershner 1995, Knight et al. 1999). After moving out of stream margin habitat, age-0 and age-1 trout in the tributaries typically use runs or complex pool habitat, with older fish selecting areas with woody debris or rootwads for cover. Most juveniles in the tributaries out-migrate at a size of 6” to 7.5” (15 to 19 cm) after spending one to two years in their natal stream, although fish of up to age-7 have been detected migrating into Bear Lake (Nielsen and Lentsch 1988, Heller et al. 2022b). Outmigration occurs over a board period and juveniles have been observed entering the lake from early May until early October, with the peak migration occurring in August (Heller et al. 2022b). Upon entering the lake juvenile Cutthroat primarily utilize nearshore water down to the thermocline (Wurtsbaugh and Hawkins 1990). Juvenile fish feed primarily on aquatic and terrestrial insects, but once the reach a large enough size they feed primarily on fish. According to Wurtsbaugh and Hawkins (1990) trout under 10” (25 cm) fed mostly on chironomid pupae in the spring and terrestrial insects in the summer. Once the fish reach 14” (35 cm) they become almost complete piscivorous, and prey heavily on the Bear Lake Cisco. These piscivorous Cutthroat have an average size of 18” (46 cm) in the lake, but fish over 28” (70 cm) have been observed (Heller 2022a). Adult Bear Lake Cutthroat typically utilize nearshore habitat and areas near the thermocline during the spring but move into offshore waters starting in August and are often found near or below the thermocline (Loo 1960, Wurtsbaugh and Hawkins 1990). Bear Lake Cutthroat introduced to Strawberry Reservoir show similar patterns and primarily forage in offshore waters during the summer, spending most of their time near the thermocline, but then utilized nearshore habitat more extensively in the fall once the thermocline had broken down (Baldwin et al. 2002).

Status

As recently as the late 1970’s a lack of information on the status of Cutthroat in the Bonneville basin led many to believe that both the Bonneville and Bear River Cutthroat Trout were extinct (Miller 1950, Hickman and Duff 1978). Fortunately, the Bear River Cutthroat has managed to persist, but at the time of its rediscovery they were relegated to a small fraction of their native range. The decline of the Bear River Cutthroat was the result of multiple factors, including over-fishing, the introduction of nonnative fish and habitat loss and degradation. Due to the continued threat from these factors and the relatively small populations, Bear River and Bonneville Cutthroat were petitioned to be listed under the Endangered Species Act in 1998 (USFWS 1998). This petition was ultimately found to be not warranted (USFWS 2008) but Bear River Cutthroat are currently considered sensitive species or species of concerns in Wyoming, Utah, and Idaho. Recovery efforts aimed at bringing the Bear River Cutthroat back from the brink of extinction continue to this day, and while it has been an uphill battle, prospects are beginning to improve for these beautiful trout.

The introduction of non-native fish such as Brook Trout, Brown Trout and Rainbow Trout, has likely been the single most detrimental impact on the Bear River Cutthroat Trout and has resulted in the loss of many pure populations. Brook Trout and Brown Trout both spawn in the fall, which allows their offspring to emerge before the spring spawning Cutthroat and thus gives them a competitive advantage. Brook Trout currently occupy at least 36 streams in the Bear River and Malad River drainages accounting for at least 30% of the streams inhabited by Bear River Cutthroat in Idaho (IDFG 2022). Brown Trout were stocked heavily in waters like the Logan and Weber Rivers in Utah in the 1940’s and 1950’s and have become well established in both watersheds (Thoreson 1949, Budy and Gaeta 2018). In contrast, Brown Trout are a more recent arrival in the rest of the Bear River watershed and were first stocked in the mainstem Bear River in 1974, but their range has been expanding they are now found through the mainstem Bear River, Thomas Fork River and several other tributary streams (IDFG 2022). Bear River Cutthroat in streams that are also occupied by Brown Trout showed clear evidence of reduced growth, as well as reduced movement (McHugh and Budy 2006) This reduced movement as well as larger Brown Trout favoring mainstem habitats and preying heavily on fish suggesting that they may disrupt the ability of Cutthroat express a fluvial life history (Meredith et al. 2014). When left unchecked, Brown Trout can completely replace native Bear River Cutthroat, as was the case in the Right Hand Fork of the Logan River. However, after removing the nonnative Brown Trout, Bear River Cutthroat show an incredible ability to rebound. For example, after Brown Trout were eradicated and Cutthroat were reintroduced to the Right Hand Fork, the Cutthroat population was able to approach its carrying capacity within just 6 years (Budy et al. 2021). Rainbow Trout, which are closely related to Cutthroat and can interbreed with them tend to be much more problematic. Due to their popularity as sport fish Rainbow Trout were stocked throughout much of the range of the Bear River Cutthroat and hybridization has resulted in the loss of the Bear River phenotype in a number of locations across their native range (Kershner 1995). Rainbow Trout currently occupy about (552 km) of river and stream habitat in the Bear and Malad Rivers and are present in 36% of streams that also contain Bear River Cutthroat and hybridization has been detected throughout much of the Bear River drainage (Campbell et al. 2007, IDFG 2022). Rainbow Trout stocking has been significantly curtailed across the basin, and to reduce the risk of hybridization, Idaho Department of Fish and Game has shifted to only using sterile Rainbow Trout in most Bear River watershed locations (Lentsch et al. 2000). Another emerging threat in the basin beyond non-native salmonids, are Smallmouth Bass which are voracious predators and have also been introduced into the Bear River drainage., While no formal predation studies have been conducted, they are believed to present a threat to the native Cutthroat.

Beyond nonnative fish introductions, habitat degradation and alterations associated with logging, agriculture, irrigation and hydropower operations have all had negative impacts on the Bear River Cutthroat. Grazing, logging and agricultural often result in higher loads of fine sediments into streams. These can be particularly detrimental to the development of eggs and alevins in the gravel and can significantly reduce the survival of eggs to hatching and juveniles to emergence from the gravel (Budy et al. 2012). In addition to increasing sediment loads by destabilizing stream banks, grazing also leads to a loss of riparian vegetation, which results higher stream temperatures, that often exceed the tolerance of the Cutthroat.

Habitat alterations have made conserving the fluvial life history of Bear River Cutthroat particularly challenging as they require interconnected habitat that is often disrupted by barriers such as dams, irrigation diversions or water quality limitations. Being relatively arid, the Bear River watershed has numerous dams and irrigation diversions including three large mainstem dams that were constructed without fish passage facilities. Many irrigation diversions were also not designed with fish passage in mind and only offer seasonal passage to migratory Cutthroat. For example, the irrigation diversion on the lower Thomas Fork River is 5’ (1.5 m) high and passage through the culverts is only possible in late fall through winter when they are not blocked for irrigation purposes. Despite numerous fish observed attempting to migrate upstream of the structure during the spawning season in May, no study fish from below the structure were observed upstream and it appears to be a full barrier from May to September (Colyer et al. 2005). Entrainment in water diversion structures can also be extremely detrimental for migratory Bear River Cutthroat if not properly screened. A study by Schrank and Rahel (2004) showed that after spawning, 23% of the Cutthroat in their study moved into an irrigation diversion ditch and subsequently died. Another study on the Covey Canal system in the Smiths Fork drainage of Wyoming showed that entrained Bear River Cutthroat were unable to leave the canal system when water levels were reduced in late summer and that 70% of the Cutthroat that entered the canal died over the summer (Roberts and Rahel 2008). In the mainstem Bear River, water temperatures often exceed the tolerance of Cutthroat and as such fluvial Bear River Cutthroat habitat usage historically varied throughout the year as the fish migrated to take advantage of favorable temperatures and feeding conditions. However, with the migration corridor significantly altered Cutthroat in the mainstem are currently relatively rare at less than 1 fish per 0.62 river miles (1 river km) and are completely absent for some stretches with suitable habitat (Hillyard and Keeley 2009).

The decline and reemergence of the adfluvial life history form in Bear Lake, provides a case study in the various factors impacting Bear River Cutthroat. Adfluvial Cutthroat in Bear Lake were once quite numerous and supported a commercial fishery that harvested between 500 lbs. to 2,000 lbs. (227 kg to 907 kg) per day (Trotter 2008). Even early on it was recognized that this fishery was not sustainable, and by 1897 Utah adopted regulations to ban commercial netting on the lake. However, similar regulations were not adopted in Idaho and as a result the commercial fishery continued. On top of the fishery, agriculture activities around the lake negatively impacted the Cutthroat through habitat loss, sedimentation and irrigation diversions that disrupted the connectivity of spawning tributaries with the lake. These irrigation diversions were not screened and resulted significant challenges for Cutthroat attempting to reach their spawning grounds as well as for adults and juveniles attempting to out-migrate to the Bear Lake. In 1912 the Bear Lake ecosystem was significantly altered when dams and a canal system on the Bear River were completed to divert water into Bear Lake where it could be stored and pumped back downstream irrigation as needed. Beyond altering the watershed dynamics in Bear Lake, the diversion also gave other fish species both native and nonnative from the Bear River access to the lake. These fish species include the Utah Chub, Common Carp, Yellow Perch, Green Sunfish, Speckled Dace and Redside Shiner. Additionally, many other nonnative game fish were intentionally introduced into Bear Lake to “improve” the fishery, with the most impactful of these being Lake Trout which were introduced to Bear Lake in starting in 1911, followed by introductions of Rainbow Trout, Brook Trout in the tributaries and other fish species (McConnell et al. 1957, Crossman 1995). The cumulative effect of these introductions was a change in the food webs in the lake, with Lake Trout fitting a similar apex predator role, preying of both juvenile Cutthroat as well as the forage fish that they depend on (McConnell et al. 1957, Ruzycki et al. 2001). Fortunately, Lake Trout in Bear Lake have not been very successful at reproducing naturally and as such have not had the same level of impacts as they have in other systems, like Yellowstone or Flathead lakes (Tolentino et al. 2015). While there has been some impact on the food web from Lake Trout, changes in the productivity in the lake appear to have more control on the fish community and as such approximately 17,000 sterile Lake Trout are stocked in the lake annually to support the fishery (Wurtsbaugh and Hawkins 1990, Tolentino et al. 2015).

Despite the fishery and changes to the ecosystem, the Cutthroat held their own in the lake until the 1920’s when the abundance dropped off sharply and when the lake was sampled between 1939 to 1941 no Cutthroat were caught (Trotter 2008). As a result, by the 1960’s it was assumed the native Cutthroat in Bear Lake were thought to be extinct and it was assumed that any remaining Cutthroat were either hybrids with Rainbow Trout or Yellowstone Cutthroat that had been planted in the lake (McConnell et al. 1957, Loo 1960). Despite this, occasionally anglers would catch Cutthroat with the distinctive sparse spotting pattern and blue coloration that Bear Lake Cutthroat were noted for and after a few of these native Cutthroat were sampled by biologists in the 1960’s, a recovery program was developed. This program started when a hatchery supplementation program initiated in 1973, by trapping upstream migrants on Swan Creek. An additional trap was later added on St. Charles Creek and was operated from 1975 to 1991 and broodstock of Bear Lake Cutthroat was developed and maintained at Mantua Hatchery (Wagner and Oplinger 2013). Eggs collected from upstream migrants that best represent native Bear Lake Cutthroat are used to produce between 150,000 and 300,000 juveniles that are planted into the lake annually and provide a harvest fishery as well as to supplement the natural population (Heller et al. 2022a). In additional to using the traps to collect eggs, starting in 1986, all Rainbow Trout moving upstream to spawn have been removed from the system to reduce the potential for hybridization (Nielson and Birdsey 1991). While this effort certainly has helped reduce hybridization, nonnative fish are still problematic in the tributaries and a recent study of fish distribution in tributaries to Bear Lake detected Brook Trout in 66% of the sampled reaches and probable Cutthroat x Rainbow Trout hybrids in 31% of the reaches (Heller et al. 2022b). Drought and irrigation withdrawals can have also had negative effects on Bear Lake and the surface elevation of the lake has decreased more 20 feet (6 m) in some years. This disrupts the food web, makes accessing spawning tributaries more challenging for Cutthroat and has been attributed to up to a 62% decline in spawning adults in some years (Glassic 2018). Additionally, during summer many of the tributary streams of Bear Lake are over utilized for irrigation and completely dry up when Cutthroat eggs are still incubating, leading poor survival rates (Lentsch et al 2000). Some irrigation structures also block up or downstream migration and may lead to spawning Cutthroat being entrained in irrigation diversions (Burnett 2003). However, progress is being made and along with the supplementation program, there have been significant conservation efforts to improve habitat, secure instream flows and screen water withdrawals to provide access through the irrigation system to spawning tributaries. The result has been a dramatic shift in the population dynamics in the lake, where only 5% of the population consisted of wild fish in 2002, by 2017 nearly 70% of the Cutthroat were wild (Heller et al. 2022a).

Today Bear River Cutthroat are in significantly better shape today than they were 50 years ago, due in no small part to the restoration efforts the various agencies and conservation groups in the basin. A major factor in the recovery of Bear River Cutthroat comes down to a cooperative conservation agreement that was adopted by state, federal and tribal governments, and agencies in the Bonneville Basin. This agreement set clear goals to reestablish Bear River and Bonneville Cutthroat population and address threats that would warrant Bear River and Bonneville Cutthroat being listed under the Endangered Species Act (Lentsch et al. 2000). The efforts that have stemmed from this agreement and the associated coordination have been largely successful and where Bear River Cutthroat once only occupied faction of their native range, they are now much more widespread. For example, in Idaho Bear River Cutthroat are believed to occupy 647 miles (1,041 km) of habitat accounting for approximately 54% of their historical distribution. This distribution has increased by 82 miles (132 km) since 2007 largely due to ongoing efforts to improve habitat and reestablish extirpated populations (IDFG 2022). Progress is also being made to restore the ability of Bear River Cutthroat to express migratory life histories, by screening water diversions and providing fish passage. A shining example of this was the removal of a derelict dam on the Bear River near Evanston, Wyoming 2022. This dam had acted as a migration barrier and blocked Cutthroat from returning upstream to their spawning habitat, but with its removal and the subsequent restoration of the surrounding habitat, the Cutthroat now have unimpeded access to the upper watershed. These changes highlight the progress that has been made to restore a fish that was thought to extinct as of the 1960’s. Today the Bear River Cutthroat are now found across much of their native range and while there certainly is more work to be done, the future is looking bright for these beautiful trout.

Description

The coloration of the Bear Cutthroat is similar to that of their close relatives the Yellowstone Cutthroat but is often even more subdued. Bear River Cutthroat are typically a brownish-olive color or a bluish color (on adfluvial fish) on the back, which transitions to a grayish to brassy/ pale yellow color on the sides, which becomes paler near the belly. Adfluvial fish are often a bluish or silvery color on their sides and are noted for the blue color on their backs and head leading them to be referred to as “blue noses”. Some individuals may display a rose color along the lateral line and on the gill plates. The colors on belly of some mature fish may become a brilliant peachy-orange color, with the same color found on the gill plates. The coloration of the lower fins ranges from a bright orange to a peach or rose color. There is considerable variation in the spotting pattern of Bear River Cutthroat, but they generally have moderate to large (sparsely distributed spots that are typically larger than those on Yellowstone Cutthroat. These spots are typically irregular shaped but may be round on some individuals and may be spread across the whole body or concentrated toward the posterior region of the fish. The spots are found on the dorsal, adipose, and caudal fins and found above and below the lateral line but are more concentrated above the lateral line. Fish in Bear Lake are noted for larger, sparser and more irregular shaped spots. Juveniles exhibit 9 to 11 oval shaped parr marks on their sides, which typically fade away on mature fish. Like other Cutthroat, these fish have a red or orange Cutthroat mark below the lower jaw.

Taxonomic Characteristics: Gill rakers average 18, with a range of 17-21. Pyloric Caeca average 43, with a range of 35-58. Scale above lateral line average 40, with a range of 34-46. Scales along lateral line average 164, with a range of 142-192 (Binns 1981).

Stream Resident Form

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Native Range

Native Trout Fly Fishing

Above: A map of the native range of the Bear River and Bonneville Cutthroat Trout. Data Source: Behnke (2002) and Trotter (2008). Below: A map of the native range of the Bonneville and Bear River Cutthroat Trout.

References

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Behnke, R. J. 1992. Native trout of western North America. American Fisheries Society Monograph 6. American Fisheries Society, Bethesda, Maryland.

Behnke, R. 2002. Trout and Salmon of North America. Chanticleer Press, New York.

Bennett, S., R. Al-Chokhachy, B.B. Roper and P. Budy. 2014. Annual variation of spawning Cutthroat Trout in a small western USA stream: a case study with implications for the conservation of potamodromous trout life history diversity. North American Journal of Fisheries Management 34(5): 1033-1046. https://doi.org/10.1080/02755947.2014.938139

Bernard, D.R. and E.K. Israelsen. 1982. Inter- and intrastream migration of Cutthroat Trout (Salmo clarki) in Spawn Creek, a tributary of the Logan River, Utah. Northwest Science 56(2): 148-158.

Binns, N.A. 1981. Bonneville cutthroat trout (Salmo clarki utah) in Wyoming. Wyoming Game and Fish Department, Cheyenne. Fisheries Technical Bulletin 5.

Bouchard, D.P., D.S. Kaufman, A. Hochberg and J. Quade. 1998. Quaternary history of the Thatcher Basin, Idaho, reconstructed from the 87Sr / 86Sr and amino acid composition of lacustrine fossils: implications for the diversion of the Bear River into the Bonneville basin. Paleogeography, Paleoclimatology, Paleoecology 141(1–2): 95–114. https://doi.org/10.1016/S0031-0182(98)00005-4

Budy, P., S. Wood and B. Roper. 2012. A study of the spawning ecology and early life history survival of Bonneville Cutthroat Trout. North American Journal of Fisheries Management 32(3): 436-449. https://doi.org/10.1080/02755947.2012.675945

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