Glacier National Park Completes 2009 Bull Trout Spawning Surveys
November 10, 2009
Contact: Amy Vanderbilt
WEST GLACIER, MONT. – Glacier National Park fisheries staff, along with federal, state and Tribal agency partners recently completed spawning ground surveys for bull trout within the park. Bull trout are listed as a “Threatened” species under the Endangered Species Act and annual spawning nest (redd) counts provide a non-invasive way to monitor relative population strength.
Each fall experienced fisheries personnel count the number of redds in pre-determined sections of stream. Not all known bull trout populations are monitored in the park, as weather and remoteness limit the park staff's ability to conduct the fall surveys in some backcountry areas.
Comparison of the count numbers over time can provide insights into long and short-term population trends and alert fishery and land managers to potential problems within aquatic systems.
Glacier hosts a rich diversity of bull trout life-history types ranging from entirely stream dwelling populations to park lake dwelling populations to those populations that inhabit Flathead Lake as adults and migrate to park streams to spawn. Glacier National Park and neighboring Blackfeet Nation host the only bull trout populations found east of the Continental Divide in the United States, located in the St. Mary portion of the Hudson Bay Drainage. Recent trends in park bull trout populations present a mixed picture of bull trout status and trends within Glacier.
There are 17 lakes on the west side of Glacier National Park that support bull trout, and these lakes represent “disjunct” populations, separate from Flathead Lake bull trout.
Although separate from the Flathead Lake bull trout populations, they face a common threat in the form of non-native lake trout. Lake trout have invaded the majority of these park lakes, presumably from upstream migration within the Flathead Basin, and currently threaten the long-term persistence of bull trout in these waters.
Spawning surveys conducted in 2009 suggest precariously low numbers of bull trout spawning in many of the lakes, including historically productive bull trout lakes such as Logging Lake, where lake trout were first discovered in 1984 and no redds were counted in 2009.
Quartz Lake is currently a bright spot among large west-side park lakes, where a strong intact native species assemblage still exists, despite the relatively recent discovery of lake trout in the lake.
Park managers in collaboration with U.S. Geological Survey researchers are currently implementing control methods to remove lake trout from Quartz Lake to conserve the native aquatic ecosystem.
The picture for bull trout on the east side Glacier National Park appears better than for the west side populations. Two St. Mary River tributaries have been surveyed for bull trout redds annually for 13 years and provide the primary means to evaluate the health of east side bull trout populations. Boulder Creek continues to support the largest spawning group of bull trout known to exist on the east side of the park.
In 2009, the redd count was slightly above the annual average of 33 redds. Kennedy Creek, the second tributary monitored in the drainage had redd counts well below average (four redds observed in 2009), although numbers over time have been fairly consistent averaging about 20. In general, where data exists on bull trout populations on the east side of the park, numbers appear to be relatively stable.
Ongoing expansion of non-native fish species into native fish habitats in Glacier National Park is a critical problem challenging the native aquatic ecosystem as well as park managers. The interaction of expanding non-native species and climate change, bringing with it anticipated changes in stream temperature, precipitation patterns, annual hydrology, and fire regimes will play a primary role in shaping the long-term future for the park’s native fish.
Developing management strategies that increase the resiliency of the native aquatic systems in the face of ongoing changes will continue to be a focus of research and management programs in the park into the future.
- NPS -