Date of Award:

5-1973

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Department name when degree awarded

Wildlife Resources

Committee Chair(s)

Robert H. Kramer

Committee

Robert H. Kramer

Committee

Clair B. Stalnaker

Committee

W. Sigler

Abstract

The objectives of this study were to determine the mortality rates of trout in Temple Fork of the Logan River during the winter of 1970-1971 and to identify factors related to trout mortality.

Trout in seven 100-m sections of the 7 3-km stream were sampled by electroshocking in October, December, February, and April. Captured trout were weighed measured and tagged or fin-clipped. Scale samples were taken for age determinations and the fish were returned to the creek.

Water temperature, snow cover, and anchor ice were monitored.

Three species of trout were found in Temple Fork: brown, rainbow, and cutthroat trout.

Daily instantaneous mortality rates were calculated for both marked trout and estimated numbers in the stream.

Daily instantaneous mortality rates, i ranged from 0.01136 to 0.06796 in marked brown trout and from -0.00964 to 0.04790 in estimated numbers of brown trout. Mortality rates were significantly different among age groups in both marked (0.025 level) and estimated numbers (0.25 level) of fish. Anchor ice was found to be a significant factor related to the mortality of Age Group 0 brown trout. A decrease of 97 percent was found in the estimated numbers of all age groups of brown trout from October, 1970 to April, 1971.

Daily instantaneous mortality rates, i, ranged from 0.01292 to 0.02833 in marked rainbow trout and -0.01175 to 0.05536 in estimated numbers. Mortality rates were not significantly different among age groups or sampling periods and anchor ice and snow cover were not significant factors. A decrease of 45 percent was found in the estimated numbers of all age groups of rainbow trout from October, 1970 to April, 1971.

Daily instantaneous mortality rates of marked cutthroat trout ranged from 0.00000 to 0.04699. In estimated numbers the rates ranged from -0.00837 to 0.06294. Mortality rates were significantly different (0.25 level) among sampling periods but not among age groups in the estimated numbers of fish. The estimated numbers of cutthroat trout of all age groups decreased by 73 percent from October, 1970 to April, 1971.

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