The Lewis River Hydroelectric Projects - PacifiCorp

Yale Park—Interpretive Sign #1 (Natural History)
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Yale Park
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Living Lakes
Yale Reservoir, and its neighbors Swift and Merwin, are habitat for a
variety of life: ducks bob on the waves and dive for food, otters and mink
swim and patter along the banks. Aquatic plants thrive in some shallow
areas, and microscopic animals and algae—plankton—drift in the water,
bursting in numbers during spring and summer.
Perhaps the most prominent of the lake inhabitants are fish. Many species
of fish swim these waters, from tiny sticklebacks to big bull trout. Some of
these species are native to the Lewis River, while others are relative
newcomers.
Kokanee (Onchorhynchus nerka)
A landlocked race of sockeye (red) salmon, kokanee are not native to the
Lewis River reservoirs. They were introduced into Yale and Merwin
reservoirs in 1957, and into Swift Lake in 1961. Today, they are stocked in
Lake Merwin, from PacifiCorp-funded hatcheries. Although Merwin
Reservoir does not have appropriate habitat for significant self-sustaining
populations of kokanee, Yale Lake does. Yale Lake does not require
hatchery stock to maintain a population of kokanee.
Bull trout (Salvelinus conflentus)
These large salmonid fish (they are actually not true trout, but members
of the char family) are federally listed as threatened throughout the
mountain west, as their populations have been strongly affected by
logging, dams, fishing, and other human impacts. Bull trout are present
in all three reservoirs, though they spawn only in a handful of creeks in
Yale and Swift.
Cutthroat trout (Oncorhynchus clarkii)
True trout, cutthroats are present and common in all three reservoirs and
their surrounding streams. There are three forms of cutthroat: resident,
which live their lives in small streams and their tributaries, fluvial, which
live in larger streams and rivers, and adfluvial, which live and grow in
the lakes but hatch and spawn in tributary streams and rivers. There are
cutthroat trout in the ocean as well. They can survive with or without
access to the sea.
Northern Pikeminnow (Ptychocheilus oregonenis)
Though they are native to the Pacific Northwest, it’s not likely that
pikeminnow were ever abundant in the Lewis River before the dams
were built. However, pikeminnows thrive in relatively still waters, and
their populations have become quite large in Merwin Reservoir.
Appendix 1: panel profiles Lewis River Draft I&E Plan page 34