Short-Term Seasonal Changes in Composition and Abundance of Fish in Sagehen Creek, California

Abstract

Abstract Direct underwater observation was used to quantify numbers and locations of eight species of fish in 100-m sections along a 1,200-m reach of Sagehen Creek, California, at biweekly intervals between 5 July and 22 September 1983. Most of the eight species exhibited significant short-term changes in abundance and reached peak abundance at different times. Total fish abundance was highest in mid-July; the Margalefindex ofdiversity was highest in mid-August. Lahontan redside Richardsonius egregius, Tahoe sucker Catostomus tahoensis, and mountain sucker C. platyrhynchus appeared to migrate from a downstream reservoir into the stream during the spawning season. In addition, fish were not distributed evenly in the study reach. All species tended to prefer pool habitat and pools were not uniformly distributed. Relative fish composition determined at long-term permanent sections by electrofishing was not significantly associated with most underwater counts made at different times or stations. This study il...