The Composition and Distribution of the Fish Populations in Sagehen Creek, Nevada-Sierra Counties, California

MASTERS THESIS:In 1951, the Fisheries Section of the Department of Zoology of the University of California, Berkeley, instituted a program of investigations concerned primarily with the cyclic nature of fish populations in high mountain streams. The ultimate aim of one part of this program is to completely evaluate the environmental and biological factors which have a direct influence on fish populations inhabiting these streams. The ultimate aim of one part of this program is to completely evaluate the environmental and biological factors which have a direct influence on fish populations inhabiting these streams. In an attempt to maintain good angling in the presence of ever-increasing fishing pressure, the fishery biologist has been forced to delve more thoroughly into the problems of population dynamics. The data obtained at the Sagehen Creek project will be used to explore the possibilities of supplementing or manipulating the environmental conditions in such a manner as to aid the production of trout, the favored fish species. As a preliminary phase in the studies of stream population dynamics, an intensive long-term study of the fishes of Sagehen Creek, Nevada-Sierra Counties, California, was initiated in June 1951. The ensuing report includes material taken from preliminary investigations during the summer of 1951 and the more extensive inventories taken during July, August, and September of 1952. This report will be concerned primarily with the distribution and composition of the fish populations inhabiting Sagehen Creek; subsequent sampling data will provide further insight on the many variables such as mortality, movement, and cyclic fluctuations. The field work to be summarized in this paper consists of ten complete stream population samples and topographic surveys for each of the individual sample sections.