A major electric utility has agreed to pay $39 million over the next 44 years to an Indian tribe whose ancestors bartered with the Lewis and Clark expedition, as compensation for damage to the salmon and steelhead fishery caused by the construction and operation of hydroelectric dams, according to an attorney for the tribe.

Avista Corp., formerly the Washington Water Power Co., represented by Paine, Hamblen, Coffin, Brooke, Miller, of Spokane, Wash., and the Nez Perce tribe of Boise, Idaho, which was represented by the Tribal Council’s Office of Legal Counsel and Denver’s Holland & Hart L.L.P., both credited a patient, two-year mediation process for a settlement that both described as fair.