The Washington Department of Fish and Wildlife (WDFW) is proposing to treat Sprague Lake with rotenone this fall to remove all fish so the lake can be re-stocked to provide a vital recreational fishery. The 1,860-acre lake, south of Interstate 90 on the Lincoln-Adams county line, was last treated with rotenone in 1985.

Proposal

WDFW is proposing to restock Sprague Lake to offer a sustainable warmwater fishery, with some trout fishing opportunity. If the lake is treated this fall, it would be re-stocked next spring with crappie, bluegill, largemouth bass, channel catfish, rainbow trout and possibly sterile tiger muskies. No walleye or smallmouth bass would be re-stocked.

The proposed treatment would restore the balance of game fish in the lake, which now has an excess number of predator species. Walleye, which prey heavily on other fish, make up 55 percent of the fish in the lake, according to a 2003 WDFW assessment. Other species include non-game carp and tench (30 percent); channel catfish and brown bullhead (6.4 percent); crappie, bluegill and perch (6.1 percent); bass (2.5 percent); and rainbow trout (1 percent).

The growing imbalance of predator fish has contributed to a decline in sport fishing. Due to predation, survival rates in trout stocked in Sprague Lake have been extremely low. Angler effort has declined: As of last year, the number of angler days on Sprague Lake was just 15 percent of the number recorded in 1987, two years after the lake was last treated with rotenone and restocked. Catch rates also have dropped: A 2006 creel survey conducted by WDFW over 10 months found catches averaging just 0.24 fish per hour, compared to a long-term average of at least one fish per hour. Despite the abundance of walleye in the fishery, anglers harvested only 8.7 percent of the number available.

Rotenone treatment

A naturally occurring substance derived from the roots of tropical plants, WDFW and other fish and wildlife agencies nationwide have used rotenone for more than 50 years for lake rehabilitation projects.

Rotenone has been tested extensively and found to present no significant health risk to people, pets, livestock or wildlife. Rotenone application is regulated by the Washington Department of Agriculture. See the American Fisheries Society website at http://www.fisheries.org/units/rotenone/ for more information.

Public comment opportunity

As with all WDFW fishery rehabilitations, the proposed Sprague Lake treatment will undergo State Environmental Protection Act (SEPA) review, including a formal public comment period this summer. Public agencies involved in the review include the Washington Department of Ecology and the U.S. Fish and Wildlife Service, along with county and tribal governments. WDFW operates its lake rehabilitation program under the provisions of a permit, issued by the Washington Department of Ecology, to ensure compliance with the Clean Water Act and State Water Pollution Control Law.

Public hearings on the Sprague Lake treatment proposal will be scheduled this summer, before a final decision is made whether to proceed in rehabilitating the lake. Meetings will be announced on WDFW's website at http://wdfw.wa.gov/.

Alternatives considered

WDFW fish managers have met with a variety or organizations and individuals to discuss options for improving fishing at Sprague Lake. Those consulted include members of the department's Inland Fish Advisory Group, statewide and local fishing organizations, owners of Sprague Lake fishing resorts and other local business, local officials and other interested parties.

Several alternatives to rotenone treatment were considered, but they are less effective or more costly. Those other options include:

• Regulation changes: Walleye fishing regulations were liberalized at Sprague Lake in 2006 (the daily catch limit was increased from five to eight fish, and the minimum size reduced from 16 to 12 inches) to boost harvest and angler effort, but a WDFW survey showed there was not enough angler effort to reduce the walleye population significantly.
  
  
• Stocking: Just two years of increased hatchery trout and warm water fish stocking would cost as much as a rotenone treatment and initial re-stocking. Net-pen fish rearing would cost more than twice as much as post-treatment annual stocking and would not be as successful.
  
  
• Mechanical removal: Removing fish with gillnets, electroshocking or other mechanical means would cost more after two years than rotenone treatment, and it could trigger an increase in carp and tench.
  
  
• Habitat enhancement: Prey fish numbers might be increased with artificial cover and other enhancements, but the cost would be more than twice that of rotenone treatment.