Waptus Bull Trout Population

Overview

The Waptus River is the larger of the two major tributaries of the upper Cle Elum River, entering the river about 5.5 miles above Cle Elum Lake. The Waptus originates as the outflow from several lakes high in the Alpine Lakes Wilderness about two miles upstream of Waptus Lake. From the outlet of Waptus Lake the river flows for approximately 8.5 miles to its confluence with the upper Cle Elum River. Most of the river is in the wilderness, with the last mile or so flowing through the Okanogan-Wenatchee National Forest (Figure 17). Numerous high-gradient creeks are tributaries to the river, all of them subject to seasonal flow depletion and all providing limited access for fish. A waterfall located on the lower Waptus River approximately 2.5 river miles above the mouth (near the Hour Creek confluence) is believed to be a complete barrier to upstream fish migration.

Population Information

Population Distribution and Life History

Bull trout were present historically in Waptus Lake. Catch records compiled by WDFW documented bull trout presence in the 1940s and early 1950s when they were evidently abundant according to anecdotal accounts. The species presence in the lake was further documented by WDFW in 1996 when a single juvenile was captured in a gill net and again the next year when an adult was caught by hook-and-line (Anderson 2001). In 2003, the USFWS sampled the lake via angling for 6-8 hours and captured numerous brook trout but no bull trout. Juvenile bull trout were reportedly observed in the Waptus River (specific location unknown) during snorkel surveys conducted by the Forest Service in 1990, but an extensive presence/absence survey conducted by the USFWS in 2003 throughout the length of the river produced only one potential bull trout observation, which was made above the lake (USFWS 2004b). A subsequent genetic analysis of a tissue sample taken from this juvenile fish revealed it to be an F₂ hybrid (see Population Status section below).

In 2017 Mid-Columbia Fisheries collected 14 eDNA samples in the Waptus River at 1km intervals (Parrish 2017). Three samples were taken upstream of the lake, 11 samples were taken downstream of the lake, and four samples were taken in Spinola Creek. Analysis showed three of the 18 samples were positive for bull trout DNA. Two of those were "weak" positives, meaning they could be the result of a far-away bull trout, or of contamination. The author suggested a re-sampling the Waptus area paired with snorkeling, fishing, or other surveys to determine presence or absence of bull trout. In 2024, a follow up eDNA survey was conducted on a finer scale, at 0.5km intervals. 50 eDNA samples were collected in the Waptus river and its tributaries (Chief Creek, Goat Creek, Hour Creek, Shovel Creek, Spade Creek, Spinola Creek, and Trail Creek) (Taylor 2024). Zero of the samples were positive for bull trout DNA. The team also spent a short amount of time fishing (~1.5 hours) near the mouth of the Upper Waptus river and caught what appeared to be a bull trout x brook trout hybrid. Subsequent genetic analysis of a tissue sample from this fish confirmed it as an an F₂ hybrid. The hybrid was noted as being triploid.

It is believed that Waptus Lake once supported a healthy and likely distinct population of adfluvial bull trout. At this point, the evidence suggests that while some bull trout may persist in Waptus Lake, a viable population may not. The timing of the 2024 eDNA effort should have captured the DNA of bull trout if adults were in the river or tributaries preparing to spawn. Because the lake was not sampled for eDNA, its possible that some adult bull trout may be using the lake but were not spawning in 2024. It is also possible that a resident component exists in the Waptus subwatershed but this has not been confirmed. Further investigation is warranted.

Natural Barriers limiting distribution

A waterfall located on the lower Waptus River approximately 2.5 river miles above the mouth (near the Hour Creek confluence) is believed to be a complete barrier to upstream fish migration. Other migration barriers exist upstream of Waptus Lake. The Chief Creek barrier falls is about 0.5 miles upstream of the confluence with the Waptus River at 47.51834, -121.21976. The upper Waptus River, upstream of the PCT crossing, is primarily fed by Shovel Creek in the late summer, as the mainstem Waptus River goes dry during low flows (last observed dry on 8/27/24 at 47.52175, -121.21727). Shovel Creek is high gradient and a fish passage barrier is likely at 47.524868, -121.215872.

Population Genetics

A genetic baseline of this population has not been evaluated due to a lack of bull trout tissue samples collected in the Waptus watershed. Only two genetic samples have been collected and both samples resulted as F2 bull x brook hybrids (Paul Spruell, University of Montana, pers comm. and Crosson 2024).

Population Monitoring

The first documentation of bull trout presence in Waptus Lake occurred during creel surveys conducted in 1940, 1948, and 1957 (Washington Dept of Game 1967). Introduced brook trout also entered the creel as early as 1940. A 1951 Washington Department of Game High Lake Survey Report states that “dollies,” eastern brook, rainbow, and cutthroat trout were found in Waptus Lake (Washington Dept of Game 1951). It appears that the lake and river were not investigated again until 1995 when the Forest Service conducted stream surveys in the Waptus River below the lake (USFS 1995). They reported that bull trout were observed while snorkeling, but data are lacking concerning the size of the fish observed and where specifically they were found.

WDFW conducted hook-and-line surveys in Waptus Lake in 1995 and no bull trout were detected (Anderson 1995).WDFW conducted snorkel and hook-and-line surveys in the Waptus River above and below Waptus Lake in 1996 and 1997 (Anderson 2001). In 1996 one juvenile bull trout was captured in a gillnet in Waptus Lake and in 1997 an adult fish (462 mm TL) was caught. No bull trout were caught in the river. Also in 1997, gillnets in Waptus Lake caught a few rainbow and brook trout and possibly a bull trout or bull trout/brook trout hybrid (Mongillo 1997).

The most concentrated effort to date occurred in 2003 when the USFWS night-snorkeled 19 randomly selected sampling units using the presence/absence protocols established by (Peterson et al. 2002; USFWS 2004b). The sampling units were located both above and below Waptus Lake; in the river below the lake, units were sampled both above and below the barrier waterfall. A total of 1.2 miles of the river were surveyed in approximately 25 person-hours of effort. Opportunistic snorkel surveys were also conducted in various reaches of the Waptus River that appeared to contain suitable bull trout habitat, including several of its tributaries, Hour, Spinola, and Spade creeks. An additional 20-to-24 person hours of effort were expended on this effort. The predominant species observed during the course of the study was rainbow trout (63%) followed by brook trout (23%). No pure bull trout were found but one F₂ hybrid was observed and captured.

Redd Surveys

There have been very few bull trout redd surveys conducted in the Waptus River. These include incomplete surveys conducted by WDFW in 1997-98 and a single survey in the reach below the barrier waterfall conducted by the USFWS in 2003. Also in 2003, the USFWS conducted a redd survey in a reach extending from Waptus Lake upstream approximately 0.6 mile. No bull trout redds were observed in any of these surveys (USFWS 2004b).

Population Status and Trend

This population was last officially rated in combination with the Cle Elum Reservoir population. The USFWS (1998) considered the Cle Elum/Waptus River population to be depressed, decreasing, and at risk of stochastic extirpation. WDFW rates the status of this stock as unknown (WDFW 1994). For the purposes of this document the status of the Waptus population should be considered unknown. As of 2015, the Waptus Lake population of bull trout is considered functionally extirpated (USFWS 2015).

Habitat

Habitat Overview

Below Waptus Lake, elevations in the Waptus River range from 2,970 feet at the lake outlet to 2,510 feet at its mouth. The alpine lakes from which the river originates are at elevations greater than 4,000 feet. The entire watershed is relatively undisturbed by human activities, the only access to it being foot and horse trails that do not impact the river. Riverine habitat and the riparian corridor are in a natural condition. The most complete description of habitat in the river can be found in a final report on bull trout presence/absence surveys conducted in 2003 (USFWS 2004b).

A variety of habitat conditions exist in the Waptus River. Below Waptus Lake a habitat transition zone is evident around RM 4.2 (about the half-way point). Below this the river has an average gradient of 1.5% and the channel displays a low degree of sinuosity. The riverbed is composed primarily of large colluvial material (boulders and large cobbles) and spawning-size gravel is scarce; pool frequency and depth are low and LWD is infrequently encountered. Above this point the average gradient drops to 0.9%, and the channel meanders much more. Here a shift towards smaller bed materials and spawning-size gravel occurs; pool frequency and depth increases significantly; and LWD (both individual pieces and extensive aggregates) abounds. Water temperatures in the lower Waptus River were suitable for bull trout in 2003, generally remaining below the threshold thought to limit the species’ distribution (15 ⁰C) during the first two weeks of September. Readings slightly warmer than this were recorded directly below Waptus Lake but these warmer water temperatures only persisted for a short distance (<0.3 mile).

Upstream of Waptus Lake the river is significantly smaller than below it in terms of both flow and average wetted width. For a distance of approximately a half-mile directly above the lake habitat conditions are exceptionally suitable for bull trout. The channel is extensively braided, disappearing frequently under massive logjams. The stream gradient was low (0.25- 0.5%), the riparian canopy was thick, undercut banks were prevalent, and LWD was abundant. Spawning-size gravels were abundant and completely free of fine sediment. Above this reach the stream gradient increases significantly, averaging 1.9%. Despite the high gradient, habitat conditions for juvenile bull trout are very good considering available pool habitat, the abundance of LWD, riparian shading and water temperature, which was much colder than below the lake. However, spawning conditions are marginal due to a shortage of suitable gravel. Given its location in the wilderness, Waptus Lake provides excellent FMO habitat for adult and subadult bull trout.

Habitat Monitoring

The Forest Service completed habitat surveys on the Waptus River in 1995 and 2003 using Hankin and Reeves protocol (Hankin and Reeves 1988; USFS 1995). In these surveys, data was collected on pool/riffle frequency, riparian and channel condition, substrate, LWD, and temperature.

Stream Temperature Data

During the aerial thermal infrared remote sensing surveys on the Cle Elum River in 2001 (Watershed Sciences 2002), temperature in Waptus River at the confluence with the mainstem Cle Elum River was recorded as 15.8 °C, one of the few tributaries with a warmer temperature than the mainstem. A long-term monitoring site on the Waptus River recorded temperature via thermographs deployed during the summer low flow period from 1994-2005 (USFS 2011b). Two other sites on the Waptus River were monitored just during the summer of 2003. Temperature data since 2005 is a monitoring gap.

Threats

Connectivity

Fish Passage Barriers

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Entrainment

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Dewatering due to flow management

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Land-use Issues

Forestry

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Agriculture and Grazing

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Recreation

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Roads and Development

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Mining

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Ecological Interactions

Brook Trout

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Other Invasive Species

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Diminished Prey Base

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Disease

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Water Quantity and Quality

Flow issues/dewatering

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Current and modeled future temperature conditions

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Fisheries Impacts

Angling Regulations/Fisheries Use/Poaching (Recreational)

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Management/Monitoring (Research)

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Other Threats

Low Population Resiliency

Climate Change

Summary of Primary Limiting Factors and Threats

A separate Threats Analysis was not completed for the Waptus population; instead it was combined with the Cle Elum River population. The highest severity threat to this population appears to be low abundance. It is uncertain whether bull trout are still present in the Waptus River drainage. A high severity threat that has likely impacted this population is the abundance of introduced brook trout. The Waptus population spawning, rearing, and FMO habitat is all contained with the Alpine Lakes Wilderness, thus limiting other possible threats.

Recovery Strategy

Population-level Recovery Strategy

The Waptus populations has been identified as a “Monitor” population with a low priority for implementing bull trout actions beyond population monitoring actions used to determine whether there are extant populations of bull trout remaining. The Waptus River is within the wilderness area and the only future actions that might be recommended would be brook trout eradication and bull trout supplementation. Brook trout eradication would be an extremely difficult undertaking, however supplementation would not likely be successful without it.

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Actions

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Recommended Actions

Waptus Lake/River Actions

• Cle Elum River #4 Determine presence and distribution in Waptus

Update Notes

2012 BTAP text copied into Yakipedia and edited to match new format inXXXXXX by Aimee Taylor. ADD LINK TO 2012 BTAP pdf placemark

Additional edits proposed by Alex Conley, Aimee Taylor and XXXXXXX small group. Reviewed, and updated and approved by BTWG in XXXXXXXXXXXXX

Specific detail on out of cycle updates: