Utilization of Half-Log Structures
as Spawning Sites for Smallmouth Bass in Norris Reservoir
J. Larry Wilson and Keith Patrick, University of
Tennessee, Department of Forestry, Wildlife and Fisheries, P.O. Box 1071, Knoxville,
Tennessee 37901-1071; Voice 423-974-7126; FAX 423-974-4714; E-Mail jlwilson@utk.edu
Keywords: habitat enhancements, spawning structure, smallmouth bass
SCUBA observations were used to evaluate the utilization
of half-logs by naturally spawning smallmouth bass. Of the 736 half-logs installed in
Norris Reservoir in 1993, 22% of the total (161) logs were evaluated weekly at three
different sites from 2 April through 25 June 1996. There were 88 line-transects, each 12.2
m in length, used as controls and positioned in non-structure areas; the transects were
located at the same water depths as the half-log structures. Species found utilizing the
half-logs for spawning were smallmouth bass, bluegill, black crappie, spotted bass, and
largemouth bass. Other species utilizing the half-logs for cover were flathead catfish and
common carp. Treatment areas produced an average of 1.9 nests per log whereas the controls
produced 0.8 nests per transect, indicating a strong preference for overhead cover for
spawning. No smallmouth bass were observed nesting around any of the control transects. In
the treatment areas all nests with eggs (61) had a successful hatch. The mean depth at
which smallmouth bass nests containing eggs were found was 3.1 m. Half-logs installed on
points had a higher percent utilization (45%) for spawning by smallmouth bass than those
located in coves (10%).
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