Responses of Fish Populations in the North Fork of the Feather River, California, to Treatments with Fish Toxicants

Abstract

Abstract Two reaches of the North Fork of the Feather River in California were poisoned with rotenone to reduce nongame fish populations, one in 1977 and the other in 1981. Both reaches had been poisoned 10 years earlier as well. Standing crops, population structure, and growth rates were determined for rainbow trout (Salmo gairdneri, Sacramento sucker (Catostomus occidentalis), Sacramento squawfish (Ptychocheilns grandis), hardhead (Mylopharodon conocephalns), smallmouth bass (Micropterus dolomieni, and riffle sculpin (Cottns gnlosns) from fish killed in test sections. The nongame fish populations recovered from the previous poisoning operations, although the unusual age structure of the sucker population (skewed to large old individuals) in the 1977 section was attributed to the earlier treatment. In the reach treated in 1977, the rainbow trout population was small and the growth rates of smallmouth bass and nongame fishes were slow compared to populations in other streams. The section treated in 1981 h...