Overview

Distribution

Global Range: (<100 square km (less than about 40 square miles)) This subspecies is native to and still occurs in the Little Kern River drainage, Tulare County, California; it occurs above the falls on the lower river (Moyle 2002).

Historically, the Little Kern golden trout occupied approximately 160 kilometers of the Little Kern River and its tributaries (Moyle 2002). By 1973, the range was greatly reduced to five headwater streams (upper Soda Springs Creek, Deadman Creek, lower wet meadows creek, Willow Creek, and Fish Creek), and an introduced population in Coyote Creek, or approximately 10 percent of the historical range (Christenson 1984, Moyle 2002). Between 1974 and 1995, a series of chemical treatments were conducted in an effort to remove introgressed Little Kern golden trout populations throughout the basin. Little Kern golden trout were then reintroduced from a few local donor populations, yet introgressed populations continue to persist in the Little Kern River drainage (Stephens 2007). The current range of the Little Kern golden trout is therefore difficult to ascertain because restocked populations continue to exhibit rainbow trout alleles at low, moderate and even high levels (USFWS 2011). The most recent genetic evidence suggests that the least genetically compromised Little Kern golden trout populations (exhibiting between 0-2 percent introgression levels) exist in Upper North Fork Clicks Creek, Upper Clicks Creek, Trout Meadow Creek, Little Kern River above Broder's cabin, and Little Kern River above Wet Meadow Creek (Stephens 2007, 2010), With the exception of Coyote Creek, a stream immediately adjacent to the Little Kern River drainage, no known populations of Little Kern golden trout occur outside of the Little Kern River watershed (C. McGuire, personal communication, 2011, cited by USFWS 2011).

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endemic to a single state or province

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Physical Description

Size

Length: 31 cm

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Ecology

Habitat

Habitat Type: Freshwater

Comments: Small, clear, cool, swift-flowing streams (Matthews and Moseley 1990). Little Kern golden trout require cool, oxygenated water with significant clean gravel for reproduction (USFWS 2011).

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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: Food primarily aquatic insects.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 20

Comments: Current distribution of pure Little Kern golden trout is limited to a few small populations (USFWS 2011).

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Global Abundance

2500 - 10,000 individuals

Comments: Due to both inconsistent count methodology and incorrect assumptions concerning the level of hybridization, the current abundance of the Little Kern golden trout cannot be determined (USFWS 2011). However, based on occupied stream kilometers and typical densities (see USFWS 2011), the overall population likely is at least several thousand.

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Life History and Behavior

Reproduction

Spawns usually in late June; males are sexually mature in about two years, females in three years (Matthews and Moseley 1990).

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Conservation

Conservation Status

NatureServe Conservation Status

Rounded Global Status Rank: T2 - Imperiled

Reasons: Small range in the Little Kern River drainage, Tulare County, California; protection and restoration have improved status, but still affected by and vulnerable to detrimental introductions of other salmonids.

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National NatureServe Conservation Status

United States

Rounded National Status Rank: N2 - Imperiled

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Global Short Term Trend: Relatively stable (=10% change)

Comments: Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably have been relatively stable.

Global Long Term Trend: Decline of 50-90%

Comments: Prior to federal listing, unhybridized populations of this subspecies were reduced to about 10 percent of the original 160 km of stream (Moyle 2002). The presence of hybrid trouts in the native range of this subspecies is still a problem (Moyle 2002, USFWS 2011).

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Threats

Degree of Threat: Medium

Comments: The principal cause of decline was hybridization with introduced coastal rainbow trout; other causes of decline included competition with non-native salmonids such as brook trout, and habitat degradation from logging and grazing practices (Christenson 1978, Moyle 2002). Mining and logging currently are not regarded as significant threats, but livestock grazing may be affecting some populations (USFWS 2011).

The most recent genetic studies, using both mitochondrial and nuclear DNA, suggest that while some populations show low levels of introgression, others continue to show moderate levels (Stephens 2007, Stephens and May 2010). With respect to the moderate and high levels of hybridization, Upper Mountaineer Creek, Alpine Creek, Jacobson Creek, South Mountaineer Creek, Shotgun Creek, Peck's Canyon Creek, Lion Creek, Tamarack Creek, Little Kern River at Burnt Corral, Lower Maggie Lake, and Silver Lake all provide serious concerns for the genetic integrity of the Little Kern golden trout (USFWS 2011).

Hybridization with introduced rainbow trout is still a threat (Moyle 2002). There is a constant threat from introductions of other salmonids by disgruntled anglers.

Due to reduced genetic variation, Little Kern golden trout populations may be particularly vulnerable to stochastic events and/or changing habitat conditions associated with climate change (USFWS 2011). Predicted outcomes of climate change imply that negative impacts on trout will occur through increases in stream temperatures, decreases in stream flow, and broader changes to the stream hydrograph (USFWS 2011).

This fish can withstand light use of streams by humans. Recreational use associated with trails and route proliferation does not appear to be a threat at this time (USFWS 2011).

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Management

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Most occurrences are in the Golden Trout Wilderness of Sequoia National Forest. Smaller areas are in either Sequoia National Park or the Sequoia National Forest. The main channel and tributary streams of the Little Kern River have been designated as Critical Habitat.

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Relevance to Humans and Ecosystems

Risks

Stewardship Overview: Restoration efforts have focused primarily on removing introgressed populations and non-native salmonids and constructing fish barriers to prevent upstream movement of non-native fishes.(USFWS 2011). Introduced populations of brook and rainbow trout have been greatly reduced via chemical treatments in the Little Kern drainage, and it is unlikely that brown trout occupy the drainage due to effective fish barriers on the Little Kern River. However, chemical treatments used to eradicate these fishes ended in 1995 and more recent data on the distribution of these introduced fishes in the Little Kern River and its tributaries are not currently available (USFWS 2011).

Revised Fishery Management Plan for the Little Kern golden trout requires: 1) periodic habitat surveys of instream, riparian, and greater landscape processes, 2) restoration of damaged habitat in portions of Fish Creek, Lion creek, Grey Meadow Creek, Coffin Meadow, Round Meadow, Jug Spring, Clicks Creek and other areas as needed and where feasible, 3) resource monitoring programs at five representative sites through periodic sampling of abiotic and biotic factors, and 4) acquisition of land area within the critical habitat boundary when possible (USFWS 2011).

USFWS (2011) made the following recommendations for conservation actions over the next five years:

1. Update the current Fishery Management Plan with a formal genetics management plan for the Little Kern River drainage with specific actions that increase genetic diversity and restore pure populations of Little Kern golden trout throughout their entire historical range. Regularly monitor Little Kern golden trout population trends throughout the drainage as guided by the most recent genetic information. If Little Kern golden trout hatchery programs are reinitiated, ensure facilities are entirely separated from rainbow trout production programs.

2. Initiate a systematic habitat monitoring program in the Little Kern drainage that regularly (every five years) assesses stream conditions throughout the drainage, including both abiotic (temperature, water quality, bank stabilization, sediment distribution, riparian vegetation recruitment, etc.) and biotic (macroinvertebrate surveys and Little Kern golden trout population surveys) factors. More sensitive stream sites, such as those located in the Little Kern and Jordan grazing allotments should be monitored more regularly (every two years).

3. Install and regularly maintain riparian fencing on streams in the Little Kern and Jordan grazing allotments, especially those in low gradient meadow reaches such as Lion, Grey, and Loggy meadows.

4. Regularly evaluate the structural integrity of stream barriers and their ability to inhibit the dispersal of non-native salmonids throughout the Little Kern River drainage (especially during high water years) and make improvements where necessary. Assess the benefits of barriers in terms of preventing non-native salmonid dispersal and compare with the potential genetic costs of these barriers in terms of reducing gene flow between naturally occurring populations of Little Kern golden trout.

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Names and Taxonomy

Taxonomy

Comments: Berg (1987) concluded that the two recognized subspecies of "O. aguabonita" are more closely related to the Kern River rainbow trout (O. mykiss gilberti) than they are to each other; hence they were regarded as subspecies of O. mykiss (followed by Moyle et al. 1989). The 1991 AFS checklist (Robins et al. 1991) and Page and Burr (1991) continued to recognize aguabonita and mykiss as separate species, but they did not comment upon the findings of Berg (1987). Behnke (1992) grouped the Kern and Little Kern golden trout as one subspecies (gilberti) of O. mykiss. He stated that they could be recognized as separate subspecies (gilberti and whitei, respectively) provided they are kept together in the same species (O. mykiss). Behnke indicated that whitei may be indistinguishable from gilberti. Behnke (2002) treated these forms as three subspecies: Golden Trout Creek golden trout or California golden trout (O. mykiss aguabonita), Kern River rainbow trout (O. mykiss gilberti), and Little Kern River golden trout (O. mykiss whitei).

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