- A segment of the Crooked River, Crook County, Oregon, was chemically treated along with sections of Ochoco Creek, McKay Creek, and Dry River from August 13 to November 5, 1963.' A total of 860 gallons of liquid synergized rotenone (Pro-Noxfish) was used to obtain toxicities up to 2.0 ppm in 87 miles of river and tributary streams.
The fish kill for the entire project listed in order of highest numbers first was suckers, whitefish, dace, squawfish, rainbow trout, chiselmouth, brown bullhead, and goldfish. A large population of mosquito fish (Gambusia) was eliminated from the Ochoco Lumber Company millpond. The State Board of Health has restocked the pond with the Gambusia. Rainbow trout were killed primarily in Ochoco and McKay Creeks. Observations on the main Crooked River revealed about 20 trout killed in the section above the city of Prineville. No dead salmonids were observed below Prineville. Large numbers of dace were killed in the upper sections of McKay Creek. It is estimated that suckers constituted from 85 to 90 percent of the total kill.
The duration of toxicity varied between river sections. Rotenone was introduced into Ochoco and McKay Creeks by constant flow stations and back-pack cans. The treatment of each stream was completed, except for sloughs and ponds, within 24 hours.
On the main Crooked River, several applications were necessary because of the cold water (42° F.). Pro-Noxfish was introduced from October 21 to November 1, 1963. The duration of toxicity continued until November 5 in the lower sections of the treated area.
Potassium permanganate was introduced at a rate of 1.5 ppm at the lower end of the project as a detoxifying agent.
Restocking of the treated areas started December 9, 1963 and continued through September 2, 1964. A total of 162,400 rainbow trout was liberated. Some of the fish liberated were of legal size, and provided angling with the opening of the angling season in April, 1964. Angling intensity increased as the fingerling plants became legal size.
Fish population studies were conducted periodically with an electroshocker to determine fish growth and.species composition.