Masters Theses

Date of Award

12-1980

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Richard J. Strange

Committee Members

J.L. Wilson, B.L. Dearden

Abstract

A typical Southern Appalachian second-order stream was partitioned into 30 meter sections which were then grouped into pure rainbow trout, mixed trout, and pure brook trout zones, and sampled by electrofishing every two months from September, 1978 to October, 1979. Each trout captured was uniquely cold-branded for identification, and scales were taken for aging. After length, weight, and section number were recorded, the trout were returned to the section from which they were taken. Overall average movement was upstream for both species, but averaged less than 2.0 sections (60 m). Zero-plus (1979 cohort) fish of both species were found in greatest densities in their respective pure zones. Two-plus and 3+ (1976-77 cohorts) rainbow trout were about equally distributed between the rainbow zone and the mixed zone, while there was 66% less density and biomass of 1+ (1978 cohort) rainbow trout in the mixed zone than in the rainbow zone.

Zero-plus brook trout grew faster in the pure brook zone than in the mixed zone, at least during the fall period. Brook trout and rainbow trout maintained equal size and equal relative growth rates until the spring (February through May) of their 1+ year at which time rainbow trout outgrew brook trout and thereafter maintained an absolute size advantage with relative growth about the same for older brook trout and rainbow trout. Total mixed zone production (1.8 g/m2/9 mo) was 62% lower than total rainbow zone production (4.8 g/m2/ 9 mo) and 44% lower than total brook zone production. The most important single group of fish within the study area was 1+ rainbow trout accounting for 88% of the total rainbow zone production; 54% of the total, positive mixed zone production; and 37% of the total brook zone production; even though they accounted for only 12% of total brook zone density. Lower total production levels in the mixed zone and brook zone were caused by an absence of 1+ rainbow trout. This absence may be the result of displacement by brook trout. Competition, therefore, may be most intense between 1+ rainbow and brook trout, probably larger brook trout.

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