Electrofishing Injury to Stream Salmonids; Injury Assessment at the Sample, Reach, and Stream Scales

Abstract

Abstract Electrofishing injury rates in rainbow trout and juvenile steelhead Oncorhynchus mykiss and juvenile spring chinook salmon O. tshawytscha were quantified in samples collected in four tributaries to, and one reach of, the Yakima River, Washington. Estimated electrofishing injury rates at the reach and stream scales were generated by using sample injury rates, derived from this study, multiplied by capture probabilities and the fraction of habitat sampled. Sample injury rates in small O. mykiss and juvenile spring chinook salmon were low. Mean electrofishing injury rate in O. mykiss samples captured in tributaries was 5.1%. Only 2.0% of the juvenile spring chinook salmon captured by electrofishing in the Yakima River were injured. Larger O. mykiss (≥250 mm fork length, FL) were injured at a significantly higher rate (27.7%) than their smaller counterparts (1.2%; P = 0.023) in the Yakima River sample. Electrofishing injury rates decreased with increasing scale from the sample to the reach and stream...