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North Cascades National Park High Lakes Fishery Management: Historic, Current, And Proposed Future Management of Sport Fish In High-Elevation Park Lakes

Category: Fish/Shellfish Research and Management - Management and Conservation

Date Published: May 2004

Number of Pages: 75

Publication Number: FPT 04-04

Author(s): Mark R. Downen


The National Park Service (NPS) has identified the need for an environmental impact statement (EIS) under the National Environmental Policy Act (NEPA) to develop a new fish management plan for North Cascades National Park (NCNP). The scope of the EIS and resulting fish management plan will include all high-elevation, natural lakes within the park and national recreation areas (NRA). The NPS invited the Washington Department of Fish and Wildlife (WDFW) to act as a cooperating agency in the development of fish management alternatives. The purpose of this document is to provide a summary of historical fish management activities for park waters, detail evolving fish management, outline current management of those fisheries by the state, and propose a management approach for the future that conserves biological integrity, minimizes impacts of fish management on native biota, and maintains sustainable quality fisheries in high lakes of the park.

The majority of high lakes within the current boundaries of the NCNP and NRAs appeared with the recession of the last glaciation, and due to topography, were not naturally colonized by fish. By the early 20th century, federal and county agencies were stocking many wilderness lakes, including high-elevation lakes within the current NCNP boundaries, with brook trout, rainbow trout, and cutthroat trout. By the time the Washington Department of Game was formed in 1933, several lakes within current park boundaries had already received fish introductions and harbored reproducing populations or were stocked periodically. Initially, fish stocking densities for lakes in the North Cascades were variable and high by current standards, and stocking frequencies were irregular since fish ecology in high-elevation lakes was poorly understood and fish management goals were largely undefined. Throughout the 1940’s, 50’s, and 60’s, the high lake fishery resource within current park boundaries continued to expand.

By the time the federal government created NCNP and the Ross and Chelan NRAs in 1968, many lakes within the park boundaries had already been stocked with fish. Many had long fishery histories, and some harbored self-perpetuating populations. The state interpreted testimony from the Congressional hearings and specific provisions of the enabling legislation of NCNP as an endorsement of its historic fish management in the park. Thus, during subsequent decades, the state continued to manage fish within the park despite an independently evolving NPS management direction and subsequent disagreement over the practice of stocking.

A long history of interagency conflict unfolded from the date of the park’s inception until the mid- 1980’s as the NPS sought to phase out fish stocking and bring waters within its boundaries into compliance with evolving national park policy. This conflict climaxed in 1985 when the NPS and the state signed a Memorandum of Understanding (MOU) nullifying previous agreements, then proceeded to derive contradictory interpretations. Lack of specificity in the agreement led the NPS to conclude they now had the legal right to phase out fish stocking while the state maintained it still operated under a previously agreed-to variance until a new formal fishery management plan was developed. In 1986 the NPS issued a new fish management policy that recognized fishing as a valid recreational pursuit within the park, but maintained that activities related to fishing could not harm the natural integrity of park lakes. The policy also usurped fish management authority from the state and called for an assessment of fish impacts on native biota.

The state would not accept this policy because it excluded the state agency and sport fishing organizations from fish management of park waters. This led to a standoff until political intervention forced the park back into a position of “co-management” with the state, and ultimately resulted in the signing of a supplemental agreement to the earlier MOU. This new agreement, called the Fisheries Management Agreement, recognized the historical fishery as a valid recreational pursuit in the park, and granted power to the state to manage fish in 40 lakes within the north and south units of the park for the next 12 years while the NPS designed and implemented a research program to assess impacts of fish on lake environments. Lakes within the NRA boundaries were not subject to this agreement because fish stocking in the NRA’s was not contrary to NPS policy, so the state continued to manage these waters under previous informal park agreements.

In addition to the constraints of the Fisheries Management Agreement, the state also implemented fishery management of park waters as it had within other designated wilderness areas. Only lakes managed prior to wilderness designation were managed for fisheries. Moreover, such waters were only stocked with species present prior to designation with methods used prior to designation. Generally, too, fixed wing stocking methods were only used where other less intrusive methods could not accomplish stocking goals.

In the early 1970’s, state fisheries biologists had begun efforts to understand high lake ecology through biological assessment of their stocking efforts. Pioneering studies led to a better understanding of carrying capacity and the need to control trout density. Refinements in stocking methods coincided with these efforts and also contributed to stable programs. As a result, stocking frequency became more regular, and for lakes without fish reproduction, somewhat less frequent. In the next thirty years, stocking densities became consistent as regular stocking programs coalesced around non-reproducing waters based on increased understanding of the response of stocked fish to their forage base. By the early 1980’s, some state biologists had developed carefully defined stocking densities and frequencies on a lake-by-lake basis. Others preferred to assign lakes into discrete management classes based on lake productivity and usage. Either way, the policy of not knowingly stocking fish on top of excessively reproducing populations and adopting conservative stocking rates became fairly universal among agency managers.

Future fish management in NCNP will be influenced by research conducted by Oregon State University (OSU) and the US Geological Survey (USGS) from 1989 through 2001 to describe high lake ecology, and demonstrate the impacts of non-native trout on native biota of mountain lakes in the park. The research found that observed densities of larval long-toed salamanders and of large-bodied copepods were significantly reduced by the presence of high densities of reproducing fish. However, effects of low densities of non-reproducing fish were only detectable in small, shallow, relatively warm, productive waters.

The researchers recommended not stocking any lake with total Kjeldahl nitrogen (TKN) > 0.045 mg/L or where water temperatures rise above 12°C. Should these guidelines be strictly followed, 23 of 27 lakes with fisheries maintained exclusively through stocking would no longer be stocked, and all lakes with reproducing populations would be considered at risk.

Before this approach is considered, some limitations to the research should be addressed including small sample size for high-productivity waters with non-reproducing fish (n = 4), the significant difference in surface area between waters with and without fish that are known to harbor long-toed salamanders, and lack of control for other factors limiting salamander abundance. Moreover, the lack of waters over 10 acres considered in the analysis, makes the extension of some statistical conclusions to the majority of fish-bearing lakes cautionary. Thresholds for where reductions in macroinvertebrate abundance constitute a significant risk to native species and processes in these lakes should also be more clearly defined.

Lingering uncertainty concerning potential risk to organisms outside the scope of research has emerged as an even greater concern with this approach. Researchers cannot assume that the relatively narrow guidelines, proposed to protect vulnerable long-toed salamanders, will maximize protection of taxonomic and ecological diversity throughout park high lakes. Managers cannot ignore the potential for unknown impacts to whole communities of aquatic organisms in larger, deeper, cooler nutrient-limited lakes, and should therefore manage for a diversity of fishless ecosystems. Finally, variable and collection-intensive water quality data should not be used to infer biological conditions when so much research has indicated the need to measure biological conditions as indicators of disturbance.

Despite these concerns, one conclusion of the research appeared robust, and consistent with other studies in Washington high lakes: the significance of fish density and impacts of excessively reproducing populations in high lake ecosystems. Conclusions on the effects of fish density and reproduction could be incorporated into a conceptual model of biological integrity that ensures that nearly pristine alpine ecosystems are not sufficiently disturbed by fish management activity that their species compositions and ecological processes deviate significantly from those expected in the absence of human disturbance. The OSU/USGS research could then be incorporated into the model with other alpine ecosystem research to conserve metapopulation dynamics of long-toed salamanders and other organisms, protect aquatic community structure and processes, and identify critical habitat and lake-specific vulnerability of native biota to fish impacts.

Such a model would consider risk factors for native biota in the context of fish presence, density and reproductive status, which can be ranked along a continuum of disturbance. Lakes in NCNP without any fish history or that have gone fishless for many years would be assumed to constitute nearly pristine ecosystems in the park, worthy of management for natural processes. These should represent a diversity of lake types to maximize protection for the greatest diversity of native biota, studied and unstudied. Based on NCNP research, lakes with low densities of stocked non-reproducing fish would be assumed, in general, to minimally impact the native biota, and be within the fish manager’s ability to control based on monitoring. In lakes with low densities and limited reproduction, fish would generally influence native biota in a manner similar to low densities of non-reproducing fish, but could occupy multiple trophic levels and persist over evolutionary time scales, largely outside the fish manager’s ability to control. Lakes stocked at high densities and frequencies would be within a fish manager’s ability to control, but would exert similar pressures on native biota as high densities of reproducing fish. At the extreme end of the fish impact continuum, the high-density, excessively reproducing populations of fish, non-native to downstream watersheds, would occupy and compete at multiple trophic levels, persist across evolutionary timescales, be outside manger’s ability to control without major intervention, and potentially disperse and interact with native species downstream.

Lakes currently holding fish could then be classified into three management categories based on the reproductive status and resulting abundance of the fish inhabiting the lake: 1) lakes with trout populations reproducing at high levels; 2) lakes with trout populations reproducing at low levels; and 3) stocked assemblages of non-reproducing trout. Within these categories any of several management approaches should be pursued based on how fish reproduction influences trout density and how that density interacts with lake-specific risk factors, such as lake depth and size, habitat complexity, elevation, isolation, and presence of sensitive species. In addition to monitoring macroinvertebrate community structure and amphibian populations, growth and condition of fish would also be used as indicators of the biological condition of lake ecosystems. Finally, the potential for supporting quality fishing opportunity should also be considered before stocking fish.

Application of this model by WDFW would initially lead to the continuation of low-risk stocking programs in 14 of 26 lakes where fisheries are currently maintained exclusively through stocking. The majority of lakes dropped from stocking would be waters with marginal fish growing potential or where risk to native biota exists due to isolation. Two historic fish bearing waters have been identified with limited risk factors that could be added to offset losses due to ecological risks in other lakes, bringing the total number of stocked waters to 18. Of 35 waters with reproducing non-native fish populations, two larger, deeper lakes have such limited reproduction that they could be supplemented by stocking; 14 with excessive reproduction could be stocked after fish removal; four could be managed for continued wild production of species native to downstream waters; and four could be considered for density control where removal appears unfeasible; and at least two lakes should be evaluated for continued management of wild non-native fish. Before any fish removal project is implemented, there should be a sound biological basis for the removal. Where wild fish do not pose a significant threat to native biota, they should be allowed to continue to provide wilderness fishing opportunity.

Interagency coordination has been a reality in wilderness fish management since the 1970’s. The most recent evidence for this has been WDFW’s acceptance of the NPS invitation to participate in the environmental review of high lakes stocking and fish management in the NCNP. Interagency cooperation can lead toward achieving goals of both agencies in the future. The most important objective from an ecological perspective would clearly be the removal of problem populations of fish from impacted lakes rather than categorically terminating stocking programs for the sake of expedience. Continuing to provide angling opportunity through biologically-based stocking of non-reproducing fish at ecologically acceptable densities would reduce within-lake impacts, offer the option to terminate stocking should problems arise, and foster a positive relationship between NPS, WDFW, and the angling community. Ultimately, all stakeholders would benefit from practical, positive relationships, and the success of a future fish management plan will depend upon interagency cooperation.