| A B S T R A C T
Progress Towards Anadromous Fish Restoration Following Dam Removals
in the Clearwater Subbasin
| The
number of dams removed in the United States has rapidly increased
in recent years. 358 dams were removed between 2000 and 2009, greater
than the total number removed in the previous 88 years. Among the
reasons prompting removal efforts, including rising maintenance costs
and safety concerns, is the critical status of many anadromous fish
populations. Increased connectivity, improved spawning gravels, and
more natural temperature and flow regimes resulting from dam removals
are expected to improve the productivity and growth of depressed anadromous
fish populations. In 1963, the Harpster Dam was removed from the South
Fork Clearwater River, followed by the removal of the Lewiston Dam
at the mouth of the Clearwater River in 1973. Historically, the Clearwater
subbasin supported robust Chinook salmon (Oncorhynchus tshawytscha)
and steelhead (O. mykiss) populations and these natural resources
played an instrumental role in the cultural life of the NiMiiPuu (Nez
Perce people). The dams at Harpster and Lewiston negatively impacted
steelhead populations, and led to the extirpation of Chinook and Coho
(O. kisutch) salmon from the basin. Natural colonization
and reintroduction efforts over the past 35 years have resulted in
increased populations of spring and fall Chinook salmon, Steelhead,
and Coho salmon. For example, the number of fall Chinook salmon redds
in the Clearwater has steadily increased from less than 10 in the
early 1990’s to over 700 in 2007. However, conditions persist
inside and outside of the basin that hamper efforts to establish naturally
self-sustaining populations. A brief history of the reintroduction
efforts within Clearwater subbasin is presented here, with lessons
for other dam removal projects aimed at anadromous fish reintroductions. |
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