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Figure 1. The food web of the Flathead River-Lake ecosystem, emphasizing those components affected by the introduction of opossum shrimp. Eagles and bears feed on spawning kokanee, lake trout eat kokanee and shrimp, kokanee and shrimp eat zooplankton (copepods and cladocerans), and zooplankton feed on phytoplankton. The organisms are not drawn to scale; they range in size from several micrometers (phytoplankton) to meters (grizzly bears).
Figure 2. The Flathead River-Lake catchment (22,241 km<sup>2</sup>) in Montana. Location of upstream lakes where opossum shrimp were introduced in 1968 (Whitefish and Ashley lakes) and 1975 (Swan Lake) are shown. Two hydroelectric dams affect kokanee spawning grounds: Kerr Dam on Flathead Lake (completed in 1938) and Hungry Horse Dam on the south fork of the Flathead River (completed in 1952). The major kokanee spawning stream and site of bald eagle concentrations is located on McDonald Creek in Glacier National Park. We refer to the catchment shown here as the Flathead River-Lake ecosystem.
Figure 6. An immature bald eagle with a kokanee salmon taken from McDonald Creek in Glacier National Park. Photo: B. Riley McClelland.
Figure 8. In Some Years, More than 500 Bald Eagles Congregated along the Four-Kilometer Stretch of McDonald Creek. Photo: B. Riley McClelland. |
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