Helena National Forest

Elkhorns Wildlife Management Unit

Bring Back the Natives

Elkhorns: Westslope Cutthroat: Bring Back the Natives

Bring Back the Natives

Elkhorn Mountains Westslope Cutthroat Trout Recovery Program

(Project #2001-0005-003)

Update Report for the 2002 Field Season

November 25, 2002

Lee Nelson
Montana Fish, Wildlife & Parks
415 South Front Street
Townsend, MT 59644
(406) 266-3425

INTRODUCTION

The 10-year program to restore viable populations of westslope cutthroat trout (WCT) to the Elkhorn Mountains was initiated in the summer of 2000. The Elkhorn Mountains Westslope Cutthroat Trout Restoration Program is a collaborative effort between the National Fish and Wildlife Foundation's Bring Back the Natives Program, Montana Fish, Wildlife & Parks, Helena National Forest, Beaverhead-Deerlodge National Forest, Bureau of Land Management Butte Field Office, and the Montana Chapter of Trout Unlimited. The overall goal of the program is to increase pure WCT distribution in the Elkhorn Mountain Range from 10 miles of stream at the initiation of the project to about 70 miles, thereby significantly reducing the extinction risk of WCT in the area (Figure 1). This effort is consistent with Montana's Statewide Conservation Agreement and Plan (1999), signed by several state and federal agencies and non-government groups, developed to ensure the long-term self-sustaining persistence of WCT in Montana. The Elkhorn Mountains restoration program includes placement of barriers to prevent nonnative trout invasion, removal of nonnative trout with electrofishing and fish toxicants, and the introduction of locally adapted, pure WCT into fishless stream reaches or streams where nonnatives have been removed.

This mid grant update report summarizes some of the important projects of the Elkhorn Mountains WCT Recovery Program during the 2002 field season, 1 June 2002 - 31 October 2002. These projects included the following efforts:

* Introduction of pure WCT eggs from Hall Creek and Prickly Pear Creek into Eureka and Little Tizer creek

* Continued removal of nonnative trout in Staubach and Muskrat creeks

* Initiating removal of nonnative trout in the South Fork of Warm Springs Creek

* Assessing the current distribution, abundance, health, and purity of remaining WCT populations

* Identifying the location for a WCT brood pond, and potential reintroduction streams

top

WCT POPULATION EXPANSION

Expanding WCT distribution in the Elkhorn Mountains by 60 miles of stream will require introduction of eggs and or live WCT into streams currently barren of fish, or into streams where nonnative trout have been removed. An objective of the overall program is to establish new populations by using "donor" WCT populations already existing in the Upper Missouri River drainage. By "replicating" existing populations localized adaptations and genetic diversity would be maintained. Prior to WCT introductions "recipient" streams are surveyed to determine the suitability of available habitat for introductions of WCT, and if any threatened or endangered aquatic invertebrate or amphibian species would be affected by WCT introductions.

Figure 1. Location of Elkhorn Mountains and project streams. Yellow lines indicate approximate distribution of pure, native WCT populations prior to initiation of the restoration program, the green line indicates a WCT population established in 1997 - 2001, and red lines indicate WCT populations established in 2001 and 2002.

top

During 2002, pure WCT eggs from pure Prickly Pear and Hall creeks were successfully introduced into Little Tizer and Eureka creeks (Figure 1). This was the first introduction of eggs into previously fishless Little Tizer Creek, and the second year of introductions into Eureka Creek. In total, 1013 viable eggs were collected from five Prickly Pear Creek females and two Hall Creek females. This is greater success than in 2001 when only 317 viable eggs were collected from two Prickly Pear Creek females. Higher success in 2002 can be attributed to collecting adults closer to actual spawning, and an increased abundance of adult WCT. Eggs were collected in June and July, fertilized on site, and then immediately transferred to a state hatchery for 3 to 4 weeks of incubation. Just prior to hatching, eggs were placed in streamside incubators in Little Tizer (n=486) and Eureka creeks (n=436). A small number of eggs were also placed back into Prickly Pear (n=61) and Hall (n=30) creeks to partially mitigate for lost reproduction. After 2 to 4 weeks of additional development, the eggs hatched and the fry dispersed from the incubators into the streams.

The introduction of eggs into Little Tizer Creek increases the distribution of WCT in the Elkhorn Mountains by an additional 2 stream miles, and helps preserve genetic characteristics of the Hall Creek population in a stream secure from nonnative invasions. The additional introductions of eggs into Eureka Creek (about 3.5 stream miles) will help increase the genetic diversity of the newly established population. Egg introductions will continue into each stream until gametes from at least 50 fish have been introduced.

Early indications suggest the small number of eggs introduced into Eureka Creek in 2001 have had an exceptionally high survival rate. In a limited amount of electrofishing, 22 age-1 WCT were collected in Eureka Creek in September 2002. These fish are believed to represent a small percentage of the total number of WCT in the stream and are a product of the 275 eggs introduced in 2001. Growth of the fish was tremendous, with the largest being 6 inches in length, and the pioneering characteristics of the species was evident as fish were found significant distances upstream from where the eggs were introduced.

While spawner availability and viability of eggs will vary from year to year, we believe this method of preserving locally adapted WCT populations has proven successful, and we will look to increase the program in 2003. Two additional donor populations, Dutchman and Ray creeks, have been evaluated for egg collection purposes. We will be proposing the introduction of eggs from these populations into Whitehorse Creek, a currently fishless stream on the eastside of the Elkhorn Mountains (Figure 1).

MUSKRAT AND STAUBACH CREEK BROOK TROUT REMOVAL PROJECTS

In 2002 we continued our efforts to reduce competition of nonnative brook trout in Staubach and Muskrat creeks (Figure 1). The abundance of WCT and their continued persistence in these streams, and elsewhere in the Elkhorn Mountains, is limited mostly by competition with nonnative brook trout. The competitive advantage of brook trout appears to occur at the young-of-the-year (YOY) stage when brook trout are markedly larger than WCT. This larger size, about 1 inch during late summer, is dictated by brook trout spawning in the fall, versus spring-spawning for WCT, resulting in brook trout eggs hatching several months earlier than WCT eggs.

We continue to use electrofishing as our primary tool for nonnative trout removals. When public concerns and litigation surrounding the use of fish toxicants (antimycin and rotenone) are resolved we anticipate utilizing these fish removal methods in future projects. However, we have been able to achieve significant reductions (> 95%) of brook trout over a relatively short period (12 months) using innovative electrofishing techniques including multiple-pass electrofishing over a several day period, and late fall electrofishing when fish are more easily captured because of their increased size and lower water temperatures. Our objective with electrofishing removals is to remove adult fish prior to spawning (September), then sub-adults as they reach maximum size in late fall.

In three years of removal efforts in Staubach Creek more than 1600 brook trout have been removed from the 1.5 mile project reach. Because of the removal efforts few brook trout remain to compete with WCT. In October 2002 only 14 brook trout were captured in the project reach - this is significantly lower than the initial removal effort in August 2000 when 766 brook trout were captured. Because of the much reduced brook trout densities, effort expended in 2002 was much less (6 days of electrofishing) than previous years.

Westslope cutthroat trout continued to respond positively to reduced nonnative competition in Staubach Creek. In August 2002, 185 WCT were captured in the project reach, which is more than a 400% increase since the initiation of the removal program. We expect significant increases in WCT abundance in the following years as the year-class dominating the population reaches maturity and spawns in the spring of 2003.

The Muskrat Creek brook trout removal project was initiated in 1997. This project has included removal of brook trout with electrofishing in a 1.3 mile stream reach and the relocation of WCT to a previously fishless upstream reach. Significant declines in brook trout density were observed after the initial 1997 removal effort (1940 removed); however, about 1000 brook trout continued to be removed during week-long efforts each of the following 3 years. To evaluate if removal protocol used in Staubach Creek would yield similar results in Muskrat Creek, we increased our removal efforts in 2001, including late fall periods. In total, 1900 brook trout were removed from the stream in the efforts of 2001.

The increased 2001 efforts resulted in a significantly reduced brook trout population. In September 2002, only 26 brook trout were captured in the project reach - down from 900 captured in September 2001. We associate the dramatic decline in the brook trout population to removing adult fish prior to spawning in the fall of 2001, and a high efficiency at removing YOY when they reached their maximum size in late fall. At a minimum, we believe the protocol we have developed for brook trout removals will help us reduce brook trout competition to very low levels over a short period of time (< 2 years), thereby allowing increases in WCT populations. Once significantly reduced, the effort required to maintain low densities of brook trout are relatively small, and we believe limited removal efforts will ultimately lead to elimination of the competing species.

The majority (n=227) of WCT captured in the Muskrat Creek project reach have been relocated to a previously fishless upstream reach that is isolated by a natural barrier; therefore, significant increases in the WCT population due to brook trout removals have not been observed in the project reach. However, WCT are expected to respond to the large reductions in brook trout observed last year. Fish transferred to the upper, previously fishless reach, have had very high survival and reproductive success. In the first sampling of this newly established population in September 2002, between 800 and 1000 fish were estimated in the 5 mile stream reach. Fish captured included those introduced in 1997, 1998 and 2001, but the majority were progeny from the relocated fish. This successful introduction has not only insured the long-term persistence of the Muskrat Creek WCT population, but also demonstrates the ability of WCT to adapt to new environments and to quickly increase in abundance in competition free waters. We anticipate these fish will eventually disperse to help reestablish a strong population in the downstream project reach.

top

SOUTH FORK OF WARM SPRINGS CREEK NONNATIVE TROUT REMOVAL PROJECT

In 2001, a population of pure WCT was "rediscovered" in the South Fork of Warm Springs Creek (Figure 1). The population, previously believed extirpated, was isolated in approximately 300 feet of stream. In addition to limited distribution and small population size (about 60 fish), nonnative trout occupying the stream immediately below the population were a significant threat of competition and hybridization. Because of the immediate risks to the WCT population a project was initiated in 2002 to reduce the abundance of nonnative trout in 1.5 miles of the stream. The short-term objectives of the project were to place a barrier to nonnative trout, use electrofishing to remove the threat of potentially hybridizing rainbow trout, and significantly reduce the abundance of competing brook trout to allow downstream expansion of the WCT population. The overall goal of the project will be to eliminate nonnative trout in the project reach through electrofishing or toxicants.

In 2002, 5511 brook trout, 1 brown trout, and 6 rainbow x WCT hybrid trout were removed from the South Fork of Warm Springs Creek with electrofishing. Brook trout were reduced from 2504 captured on the first electrofishing pass to 304 on the last (5 passes total). Because of the relatively high brook trout densities at the initiation of the project, we expect that a moderate number remain; however, we did see significant reductions in adult fish prior to spawning and expect reduced reproduction will lead to a much smaller population next year. This should allow successful downstream dispersal of the WCT population in the next several years. As important, we believe the efforts removed all potentially hybridizing trout existing in the project reach.

To prevent further nonnative trout invasions we constructed a barrier to upstream moving fish by modifying existing cascades with a small wooden drop structure. Along with continued electrofishing removals in 2003, we will insure the success of the barrier by attaching a short flume that will create a 5 foot plunge.

ASSESSING REMAINING WCT POPULATIONS IN THE ELKHORN MOUNTAINS

Implementation of the Elkhorn Mountains WCT restoration program includes monitoring of the 7 remaining WCT populations and the species that coexist with them. Population monitoring information will help prioritize restoration efforts by identifying which WCT populations could serve as "egg-donors", whether nonnative trout have moved into new areas, and to set baseline population indexes to determine the effects of restoration efforts on all fish species distribution and densities.

In general, in 2002 the WCT populations in the Elkhorn Mountains (Figure 1) continued to be negatively impacted by drought. Due primarily to restoration activities the Staubach and Muskrat creek populations have increased in number and distribution, and will respond even greater with better water years. Hall and Prickly Pear creeks, current sources of eggs for introduction efforts, appear to be stable or slightly increasing in number. Adults continue to be at lower than historic densities in these streams, mostly from over-winter mortality, while juvenile fish are relatively abundant.

Dutchman Creek, historically one of the more robust WCT populations in the mountain range, appears to have had the greatest reductions because of drought. This stream lacks large numbers of deep pools, and over-winter survival of larger fish appears to have been much reduced over the last several years. In addition, in 2002 brook trout were captured for the first time within the reach previously only occupied by WCT. While the brook trout are very rare, they are an immediate concern, and they indicate continued expansion of nonnatives in the mountain range where barriers are not sufficient. We will propose brook trout removal efforts in 2003 to prevent additional increases in the population.

PROPOSED PROJECTS FOR 2003: BROOD POND, WHITEHORSE CREEK WCT INTRODUCTION, AND NONNATIVE SUPRESSION

Small population size may prevent efforts to directly replicate some existing WCT populations. To preserve some of the unique genetic attributes of these populations we have initiated an effort to establish a brood stock comprised of WCT populations from the upper Missouri River drainage. The project will include collecting eggs or live fish from several local populations, and rearing them in a secure pond. Once these fish mature, eggs would be collected and back-crossed to wild populations for restoration efforts. The benefits of a brood pond would be to reduce impacts on donor populations, enable the collection of a large number of eggs for restoration efforts, and to preserve unique characteristics that otherwise would be impossible to replicate because of small population sizes.

In the fall of 2002, we secured the use of a 1.5 acre private pond that we hope to develop as a WCT brood stock rearing facility in the summer of 2003. Our goal is to use at least four WCT wild donor sources to start the brood stock; these include Hall, Prickly Pear, and Dutchman creeks from the Elkhorn Mountains, and Ray Creek from the Big Belt Mountains. Ray Creek is a large WCT population that will be used as the main source of eggs to be fertilized with Elkhorn WCT males. Eggs from the established brood should be available for restoration efforts by 2006.

In the continuing effort to expand WCT distribution in the Elkhorn Mountains we are proposing to introduce WCT into Whitehorse Creek (Figure 1) in the spring of 2003. The stream is currently fishless, isolated by a dry stream reach, and has favorable habitat conditions in 3 miles of stream for a small WCT population. Similar to projects in Eureka and Little Tizer creeks, this project would include the collection and introduction of WCT eggs to the stream. Preliminary donor sources are Dutchman and Ray creeks.

We will also continue with our nonnative trout suppression efforts in 2003. Removal efforts in Staubach and Muskrat creeks will continue at a much reduced level as nonnative populations have practically been eliminated. The South Fork of Warm Springs project will be our focus of effort in 2003. With the second year of removals we anticipate the brook trout population will be reduced by > 95% in the 1.5 miles project reach. We will also be initiating two additional removal projects in the McClellan Creek drainage and in Dutchman Creek.

CONCLUSIONS

The efforts of the 2002 Elkhorn Mountains Westslope Cutthroat Trout Restoration Program field season helped to reduce the extinction risk of WCT in the mountain range. Westslope cutthroat trout expanded in number and distribution in spite of drought conditions that continue to constrain most populations. Egg collection and introductions in 2002 were very successful and increased the distribution of WCT in the mountain range by about 5.5 miles. Efforts to reduce nonnative trout competition continue, and significant reductions were seen in their abundance where electrofishing removals were employed; concurrently, WCT continue to increases in abundance and distribution in these streams.

In 2003 we will continue with expansion of the existing WCT populations, including to one additional stream. Nonnative trout removal efforts will continue, and we will add two additional removal projects to the program. We will also establish a WCT brood pond that will help us conserve unique genetic attributes for future restoration projects.

ACKNOWLEDGMENTS

Efforts to restore viable populations of WCT to the Elkhorn Mountains have been possible because of the cooperative efforts of the National Fish and Wildlife Foundation's Bring Back the Natives Program, Montana Fish, Wildlife & Parks (FWP), Helena National Forest, Beaverhead-Deerlodge National Forest, Bureau of Land Management Butte Field Office, and the Montana Chapter of Trout Unlimited. Jodie Canfield, Helena National Forest, and Ron Spoon, FWP, initiated and developed the overall 10-year restoration plan. Numerous individuals have helped implement the on-the-ground efforts of this program including Doug Rider, Ben Whiteford, Greg Gibbons, Mike Korn, Cy Rosenthal, Patrick Kolar, Alexander Alexiades, Brad Shepard, Bruce Rich, Ken McDonald, Bob Snyder, Mark Sweeny, and Ken Staigmiller - all from FWP, and Len Walch and Archie Harper from the Helena National Forest.

top

USDA Forest Service - Helena National Forest
Last Modified: Monday, 25 June 2007 at 13:31:19 EDT