Fact Sheet: Mountain Lakes Restoration

Working to ensure people will be able to fish for native fish, in their native habitats, in the

North Cascades National Park Complex, for generations to come.

The mountain lakes of North Cascades National Park Complex were naturally fishless.

Historically, the mountain lakes of North Cascades National Park Complex were naturally free of fish due 

to the steep and rugged nature of the glacially carved valleys and abundant waterfalls. In the absence of 

fish, these lakes developed unique ecosystems where frogs and salamanders have become keystone 

predators bridging terrestrial and aquatic habitats. North Cascades National Park Complex currently has 

62 lakes containing introduced fish. Research conducted here and elsewhere has demonstrated that 

introduced fish have a negative impact on the amphibians, insects (such as caddisflies) and zooplankton, 

which all need these lakes to survive.

The primary concerns of North Cascades National Park (and the National Park Service) are the

preservation and restoration of native ecosystems and species for the enjoyment of future 

generations.

As a unit of the National Park Service, North Cascades National Park Complex is charged with the 

preservation and restoration of the natural ecosystem. The park does a wide range of work to protect 

and restore the aquatic ecosystems of the North Cascades. This includes supporting research, 

monitoring indicators of ecosystem health, habitat restoration and active fish population management. 

The priority is to support native aquatic species, and the largest area of work has been and will continue 

to be the preservation and enhancement of native fish in their natural habitat – to support both the 

ecosystem and opportunities for anglers to enjoy catching native fish in their natural habitat. 

The freshwater habitats managed by North Cascades National Park provide some of the best habitat for 

several regionally important species of the Pacific Northwest. The Skagit, Chilliwack, Cascade and 

Stehekin watersheds provide some of the most protected habitat for Chinook, Coho, Sockeye, Steelhead

and Chum salmon, coastal and westslope cutthroat trout, rainbow trout and the Federally threatened 

bull trout in a landscape experiencing rapid change due to human population growth and development.

Tinkering with nature (stocking non-native fish) is risky.

Introducing fish into non-native habitats impacts both native fish populations and ecosystem functions. 

In particular, the introduction of Eastern brook trout into the heart of the North Cascades is now 

threatening a prime refuge for bull trout. Additionally, lakes with reproducing populations of introduced 

fish displace native frog and salamander populations and disrupt natural food webs. In both of these 

examples, people thought they were improving the natural environment by stocking non-native species 

of fish. But, instead, the result has been negative impacts to the ecosystem and unhealthy and nonrecreationally-rewarding fisheries.

Active Restoration 

Of the lakes that contain introduced fish, 27 contain high-density reproducing populations. Research 

conducted in North Cascades National Park Complex has demonstrated that these populations of fish 

are the most damaging to native ecosystems. Reproducing fish populations in naturally fishless lakes 

tend to over-populate these systems, causing the fish to outstrip their food resources. Not only does this 

Fact Sheet – Mountain Lakes 

Restoration

National Park Service

U.S. Department of the Interior

North Cascades National Park Complex
eliminate or reduce the abundance of many of the native species, it also leads to unhealthy and poorquality fish. 

Of particular concern are situations where non-native Eastern brook trout threaten native bull trout. 

Where Eastern brook trout have established reproducing populations in lakes, these fish have the ability 

to harm downstream federally threatened bull trout populations by cross-breeding with them and 

diluting their genetics. 

Lakes with high-density reproducing fish populations are priorities for active restoration and recovery of

native biological communities and natural food webs as well as the protection of bull trout populations. 

Park biologists are developing methods to restore these lakes while minimizing the impacts native 

species. 

Fishing will continue

North Cascades National Park has numerous high-quality fishing opportunities for anglers to catch native 

fish in their natural habitats. Salmon can be caught in the Skagit River and cutthroat trout in the 

Stehekin River and its tributaries. Native rainbow trout can be caught in Ross, Diablo and Gorge Lakes. 

And the NPS will continue to work to preserve and enhance these fisheries and fishing opportunities.

Of the lakes that contain introduced fish, the restoration of 26 of them will occur through the simple act 

of discontinuing fish stocking. Not only is this a cost-effective and efficient means of recovering the 

natural biological communities, it will also allow anglers to continue to fish these lakes for years until all 

of the fish are caught or die of natural causes.

There will also remain far into the foreseeable future numerous opportunities for anglers to seek the 

challenge of fishing mountain lakes given the difficulty of removing non-native species in large lakes 

such as Bear, Berdeen, Lower Berdeen, Doubtful, Green, Hanging, Hidden, Monogram, Sourdough, 

Stout, Lower Thornton, and Trapper lakes.

Working to preserve natural ecosystems and provide access for generations to come

North Cascades National Park Complex staff are testing methods to actively restore nine lakes with high 

density reproducing fish populations. The goal of these efforts is to develop restoration methods which 

will enable the recovery of native ecosystems while minimizing the impact to non-target organisms. 

Spawning habitat exclusion is being tested in one lake, targeted gill netting is being tested to remove 

fish from six lakes, and antimycin was used in two lakes (Upper and Lower Blum) to restore native 

ecosystems and protect federally threatened bull trout. 

North Cascades National Park Complex will continue to support high-quality fishing opportunities to 

catch native fish in their natural habitat. To this end, the park is working with the Washington State 

Department of Fish and Wildlife to monitor native fish populations and collect water quality data on the 

Skagit and Stehekin rivers and Gorge, Diablo, and Ross lakes. The park will also continue to provide 

access to fisheries with boat ramps, docks, trails, campgrounds, and information. The park is produced a 

new Fishing Guide to The North Cascades to help share where opportunities exist for native fisheries.