Salmonid Abundance in Mill Creek Between the Mill Creek Diversion Dam and the Mill Creek Division Dam

摘要

Fish movement in the Mill Creek flood control channel may be restricted when flow drops to summer base flow levels. As a result, construction of a low flow channel is being considered to improve fish passage in Mill Creek. Salmonid abundance was estimated for the U.S. Army Corps of Engineers to evaluate the cost/benefit of constructing the low flow channel. To estimate salmonid abundance, the U.S. Fish and Wildlife Service with assistance from the Washington Department of Fish and Wildlife and the U.S. Army Corps of Engineers designed and conducted simple random sampling surveys using snorkeling in the flood control channel of Mill Creek during June, July and August of 2009. We attempted to quantify the detection probability of the snorkel surveys through multiple pass, depletion electrofishing, but were unsuccessful with this method. As a result, survey estimates represent minimum abundance estimates for the study area. The estimated minimum salmonid abundance was 410, 538 and 407 fish during June, July and August, respectively. Although detection probabilities could not be estimated, qualitative observations suggest there may have been considerably more salmonids present during June when the abundance estimate was 410 fish.