Ahtanum Bull Trout Population

Overview

Ahtanum Creek is a tributary of the Yakima River that enters the river just south of the city of Yakima at RM 107. The stream is composed primarily of a North and a South Fork, which merge at around RM 23 to form a single main channel. The North Fork is approximately 23 miles in length while the South Fork is approximately 15 miles. Another fork, the Middle Fork, enters the North Fork at about its halfway point.

Population Information

Population Distribution and Life History

The Ahtanum Creek drainage supports what is currently treated as a single local population of bull trout. There are known spawning areas in the upper reaches in all three forks and Shellneck Creek, a tributary to the North Fork (Figure 3). However, there is a falls at RM 2.5 on the South Fork Ahtanum Creek that is believed to be a barrier to upstream migration. Juvenile rearing occurs in the upper reaches and may extend all the way to the confluence of the forks. Adults are assumed to utilize the entire drainage as FMO habitat. It is possible that some adults migrate seasonally into the mainstem Yakima River when conditions (i.e., water temperatures) are suitable (see below), but timing of migration from FMO areas to spawning reaches is unknown.

Currently this population is considered a resident/fluvial life history type. Low stream flows due to irrigation withdrawals, thermal barriers, and habitat conditions in lower Ahtanum Creek limited migratory access to the mainstem Yakima River as early as 1880 with the construction of numerous irrigation diversions. These conditions persisted through the 1900s and beyond. Migratory conditions have improved in the last decade but there is very limited evidence of fluvial connectivity. A smolt trap has been operated by the Yakama Nation at the mouth of Ahtanum Creek since 2000 to enumerate juvenile steelhead and coho leaving the drainage (Anderson 2010). Only one out-migrating adult bull trout has been caught in the trap during its operation.

Population Monitoring

WDFW electrofishing surveys documented the presence of bull trout in the North and Middle forks of Ahtanum Creek in 1993 (Anderson 1993). During that same year redd surveys within established index areas began in the North Fork Ahtanum Creek (including Shellneck Creek). The Yakama Nation documented bull trout in the South Fork Ahtanum Creek in 1998 and 2000 (Gullett 2001). Redd surveys were initiated on the Middle Fork Ahtanum Creek in 1996 and on the South Fork Ahtanum Creek in 2000; however, index areas were not fully established and complete surveys were not conducted on these forks until 2002 and 2001, respectively (Appendix B). The Yakama Nation conducts the surveys on the South Fork Ahtanum Creek and WDFW is the lead on the other forks.

Snorkel surveys were conducted in 2000 as part of a statewide project to predict how habitat variables affect juvenile bull trout (Dunham and Chandler 2001). There were also snorkel surveys in 2001 in association with collection of genetic samples for Reiss (2003). In 2002 genetic samples were collected during electrofishing surveys as part of a statewide WDFW bull trout genetics baseline (Small and Martinez 2011). WDFW day and night snorkeled and electroshocked the North Fork and Shellneck Creek in 2003 as part of a project to develop a bull trout presence/absence sampling protocol (Hoffman et al. 2005). Larsen et al. (2003) examined these data in more detail with Peterson et al. (2005) providing final analysis.

Adult bull trout have been captured in two fish salvage efforts. WDFW collected 5-6 resident bull trout at the Bachelor-Hatton construction site on mainstem Ahtanum Creek in 1994 (WDFW 1996) and Scott (2010) captured two bull trout during the removal of a low dam at the North Fork Ahtanum Creek USGS gage site.

Mizell and Anderson (2010) investigated the migratory behavior of adult bull trout in the Middle and North forks of Ahtanum Creek. None of the radio tagged fish migrated outside of the Ahtanum Creek drainage. Only one fish moved below the confluence of the North and Middle forks of Ahtanum Creek.

Redd Surveys

The Ahtanum Creek population spawns primarily during the month of September. Complete redd counts were first recorded in established index areas on the North Fork Ahtanum Creek in 1993, the South Fork Ahtanum Creek in 2001, and the Middle Fork Ahtanum Creek in 2002. The index area on the North Fork is 1.9 miles long with the lower 0.5 miles of Shellneck Creek (a high elevation tributary) also surveyed. The length of the index areas for the Middle Fork and South Fork are 2.0 and 2.7 miles, respectively. Annual redd counts are presented graphically in Figure 2. Considering the last 10 years (when data are available for all three forks), this population appears small and generally getting smaller. Redd numbers steadily declined over the first four years of that period from a high of 36 in 2002 down to 14 in 2005. With the exception of 2008 (seven redds), counts have held between 16 and 18 since 2005. Noteworthy is the steady decline in the number of redds observed in the North Fork over the last decade. In contrast, the Middle Fork has experienced an increase in spawning activity over the last four years.

Population Status and Trend

The USFWS considers the Ahtanum Creek population to be depressed, decreasing, and at risk of stochastic extirpation (USFWS 1998); the WDFW rates the status of this population as critical (WDFW 2004). If future genetic analysis determines that each of the forks represents a distinct, isolated population, each of these populations would warrant a depressed or critical status.

Genetic analysis concurs with this lack of connectivity to the larger fluvial system (Yakima or Naches rivers). Genetic samples were collected from all tributaries in the Ahtanum Creek drainage and were analyzed as one population. The population was unique when compared to all the other Yakima Basin populations and did not cluster with the Naches River fluvial populations (Reiss 2003; Small et al. 2009).

Habitat

Habitat Overview

The area inhabited by bull trout on Ahtanum Creek ranges in elevation from 960 feet at the mouth to about 5,000 feet at the upstream end of the spawning area in the North fork (all elevations provided in this document are above mean sea level). The known spawning, and presumably primary juvenile rearing, habitat in all three forks occurs in reaches at higher elevations (4,200-5,000 feet) although it is probable that rearing habitat extends downstream to the confluence of the forks (elevation ~2,100 feet). Above the forks, land ownership consists primarily of Washington Department of Natural Resources (DNR) lands and commercial timber company holdings; Yakama Reservation lands occur south of the South fork for its entire length. Habitat conditions in the Ahtanum Creek watershed were described in detail in the Salmonid Habitat Limiting Factors Analysis for the Yakima River watershed conducted by the Washington State Conservation Commission (Haring 2001).

In the upper watershed, timber harvest (and associated roads), livestock grazing and heavy recreational use have degraded habitat conditions. Negative impacts on channel condition (pool frequency and depth, LWD presence), substrate condition (resulting from increased fine sediment load) and riparian condition have all occurred. Impacts from livestock grazing have lessened considerably over the last decade but forest practices, road density and recreational impacts remain a concern. The latter is primarily associated with two DNR campgrounds located on the banks of the North Fork, which contribute to bank erosion and riparian damage, and the construction of recreational dams that impede or prevent fish passage.

In addition to the FMO habitat available in the three forks of the Ahtanum Creek, the 23 miles of the mainstem below the confluence of the North and South forks are utilized as well. Lands along the mainstem are almost entirely privately owned to the north of the creek with the Yakama Reservation to the south. The primary land use is agriculture with rural residential housing and some industrial development in the lower part of the creek. Irrigation development began in the mid-1800s and by the early 1900s there were over 100 diversions, primarily on the mainstem Ahtanum Creek. Most, if not all, were unscreened. Today there are two main irrigation projects on the creek: Ahtanum Irrigation District (AID) which serves the agricultural lands north of the creek, and the Wapato Irrigation Project (WIP) which serves the Yakama Reservation lands to the south. In addition, there are numerous smaller pump and gravity diversions, which are private. The effects of agricultural development on fish populations and habitat have been profound. Haring (2001) provided extensive detail regarding these effects. Since the document was published there have been significant improvements with respect to screening diversions although a small number remain unscreened. There have also been improvements regarding instream flow, the most significant being the agreement with the WIP to provide a minimum flow of 10 cubic feet per second (cfs) in a 7-8 mile reach that was annually dried up between mid-July and mid-October. These improvements notwithstanding, the mainstem remains flow depleted in the summer and early fall and other problems exist as well. The creeks floodplain has been disconnected by dikes; channel condition is poor due to extensive bank erosion and the lack of LWD; riparian condition is poor due to livestock grazing, residential development and flow depletion; and summer water temperatures are unsuitable for bull trout due to riparian disturbance, floodplain disconnection, and flow depletion.

Habitat Monitoring

USGS reported the effects of Mount St. Helens eruptions on several watersheds, including Ahtanum Creek (Lee 1996). Chesney (1998; 2000) monitored channel condition and functioning of wood for a long-term habitat monitoring program on DNR lands. For the Dunham and Chandler (2001) study referenced above, temperature, large wood, gradient, wetted channel width, mean depth, maximum depth, undercut banks, and substrate were measured within designated reaches.

The WDFW, through Fish Restoration and Irrigation Mitigation Program (FRIMA) funding, conducted an extensive fish passage and diversion screening survey on Ahtanum Creek from March-August 2003. This survey consisted of an inventory of all fish passage barriers and water diversions encountered within the watershed (Kohr et al. 2004).

The Department of Ecology facilitated the Ahtanum Creek Watershed Restoration Program (ACWRP) which was intended to resolve water resource problems in the watershed by providing a unified program to restore stream flows and fish habitat and to improve water supply for irrigation (Ecology 2005). This resulted in a detailed plan for habitat work in the watershed but dedicated funding has not been secured.

The Washington Department of Ecology (DOE) monitored water quality at the mouth of Ahtanum Creek (Fulbright Park) in 2009. Temperature and fecal coliform exceeded state water quality standards for several months during the summer irrigation period (Ecology 2009). The U.S. Geologic Survey (USGS) has also collected water quality data from 1973-2000 at five sites on Ahtanum Creek, from the mouth to Tampico (USGS website). The Yakama Nation has collected other temperature monitoring data in the Ahtanum Creek drainage (G. Morris, YN, pers comm). Nine sites along the Middle, South and North forks of Ahtanum Creek, as well as several tributaries were monitored as year-round sites from 2003-2006. There has been no water temperature data collected in Ahtanum Creek since 2006; this is identified as a data gap.

Threats

Connectivity

Fish Passage Barriers

Threat Severity:

Entrainment

Threat Severity:

Dewatering due to flow management

Threat Severity:

Land-use Issues

Forestry

Threat Severity:

Agriculture and Grazing

Threat Severity:

Recreation

Threat Severity:

Roads and Development

Threat Severity:

Mining

Threat Severity:

Ecological Interactions

Brook Trout

Threat Severity:

Other Invasive Species

Threat Severity:

Diminished Prey Base

Threat Severity:

Disease

Threat Severity:

Water Quantity and Quality

Flow issues/dewatering

Threat Severity:

Current and modeled future temperature conditions

Threat Severity:

Fisheries Impacts

Angling Regulations/Fisheries Use/Poaching (Recreational)

Threat Severity:

Management/Monitoring (Research)

Threat Severity:

Other Threats

Low Population Resiliency

Climate Change

Summary of Primary Limiting Factors and Threats

The highest severity threats to this population, forest management and low abundance, as shown in Table 6, result from land ownership patterns—private and DNR forest lands that have degraded habitat conditions and presumably lowered population viability (Table 5). Passage barriers, resulting from low flow conditions in the lower reaches (i.e., altered flows) and recreation dams in the upper spawning reaches, also appear to be limiting bull trout productivity in this system. There are multiple threats of unknown but potentially significant severity including: angling, entrainment, prey base and recreation. Further monitoring work is necessary to confirm the severity of each of these threats.

Certain threats, which are commonly associated with the Ahtanum Creek system (agriculture and grazing) were rated as unknown in the analysis but were not considered significant. Agriculture, though present in the lower FMO reaches, was not found to have direct mechanisms for affecting the bull trout population. Instead the potential effect is indirect via water quality issues or riparian degradation, although neither is considered significant. Grazing allotments are present in the spawning and rearing reaches. However, riparian fencing has reduced the severity of this threat to insignificant. A road along the length of the mainstem Ahtanum Creek in the FMO habitat is believed not to present a significant threat. There are no known areas of natural dewatering, or introduced brook trout, or mining, and the extent of habitat is not limiting.

Recovery Strategy

Population-level Recovery Strategy

This population has been identified as a high priority “Action” population (see Prioritization of Actions). The highest priority recovery actions are those that improve habitat and access to habitat in the upper spawning and rearing reaches and those that restore instream flow and reduce entrainment in the lower FMO reaches. To address threats to the Ahtanum Creek bull trout population, it will be critical to work with staff at the DNR to implement road closures and habitat restoration projects in important bull trout rearing areas. Protection and restoration of downstream FMO habitat will involve partnerships with private landowners. This is an area where habitat improvements are currently being completed based on their importance for anadromous species. Addressing the current Low Abundance threat by continued population monitoring will be critical, as will understanding the movement patterns between forks. This is a candidate population for evaluating the feasibility of supplementation (see Appendix D). Outreach is a priority in order to document angling pressures and to educate anglers, recreationists, and landowners throughout the watershed. The Broad Scale actions that apply to the Ahtanum Creek populations include: Restore Healthy Salmon Populations.

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Actions

Future link/ iframe to PowerApp will go in this section.

Completed Actions

• Screened nine unscreened gravity diversions and side channel construction (2001-2008).
• Riparian exclusion fence constructed within grazing allotment in spawning areas of the North Fork Ahtanum Creek in 2004.
• Cattle grazing allotment in Middle Fork Ahtanum Creek not renewed in 2008.
• Passage barrier removed at North Fork Gaging Station in 2010 (YTAHP).
• Herke fish screen (SRFB project 10-1764). (Project was funded in 2010 and should be completed in Fall 2012.)
• The North Yakima Conservation District screened three unscreened (non-compliant) pump diversions in 2005.
• Agreement between Yakama Nation and principle irrigators to maintain a minimum of 10 cubic feet per second (cfs) instream flows.
• Fishing regulations have been implemented to protect bull trout in Ahtanum Creek (see Appendix F).

Recommended Actions

For additional detail on the actions listed below, see Actions Detail (starting on p. 164)

Population Scale

·      Ahtanum Creek #1: Instream and floodplain restoration.

·      Ahtanum Creek #2: Address forest health in Ahtanum Creek watershed.

• Ahtanum Creek #3: Relocate road adjacent to Shellneck Creek and reduce road densities throughout the forested area of the drainage.
• Multiple Populations #4: Evaluate supplementation (see Appendix D).
• Ahtanum #5: Increase instream flows via water conservation and diversion consolidation in the mainstem Ahtanum Creek.
• Multiple Populations #1: Monitor for recreational dams on an annual basis and remove as necessary.
• Multiple Populations #1: Outreach on bull trout conservation issues (landowners, recreationists, anglers, school groups, and others).
• Ahtanum Creek #7: Ensure all pump and gravity diversions are adequately screened including all three Herke Ranch diversions (the last unscreened open ditches).
• Multiple Populations #5: Carcass analog placement if pilot studies demonstrate success.
• Ahtanum Creek #8: Close or relocate Tree Phones Campground.
• Ahtanum Creek #9: Close Snow Cabin Campground and restore the site.

Population Monitoring

• Multiple Populations #2: Continue redd surveys within the established index areas of all forks to monitor long-term abundance trends.
• Ahtanum Creek #4: Evaluate movement patterns and genetic connectivity between forks.

Baseline Habitat Monitoring

• Multiple Populations #3: Continue temperature monitoring throughout Ahtanum Creek drainage, expanding as necessary.

Implementation Monitoring of Completed and Recommended Actions

• Ahtanum Creek #10: Monitor effectiveness of cattle exclusion fencing in the North and South forks.
• Ahtanum Creek #7: Monitor condition and effectiveness of fish screens on irrigation diversions.

Threats Research & Monitoring

• Ahtanum Creek #6: Habitat surveys in areas affected by grazing, forest management, agriculture, or residential development.

Actions Identified in YSRP that would benefit bull trout

(Yakima Basin Fish & Wildlife Recovery Board 2009)

Naches River Action #24: Protect instream flow improvements in Ahtanum Creek

Naches River Action #25: Develop off-channel storage in Ahtanum Creek

Naches River Action #26: Minimize irrigation conveyance loss in Ahtanum Creek

Naches River Action #27: Ahtanum Creek floodplain and side channel restoration

Naches River Action #28: Protect Ahtanum Creek riparian areas to lessen developmental impacts

Naches River Action #29: Reduce livestock impacts on Ahtanum Creek riparian areas

Update Notes

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