8097

• UCREFRP Catalog Number: 8097
• Author: American Fisheries Society.
• Title: Proceedings of the 18th Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
• USFW Year: 1983.
• USFW - Doc Type: March 2-3, 1983.
• Copyright Material: NO

to test for significant differences between mean within week and mean between
week population estimates for the various streams.

RESULTS

Table 2 shows mean within week and mean between week population estimates
for several streams in Wyoming. Average within week population estimates
were only 75.1 and 54.0% of the between week estimates for rainbow and brown
trout, respecitvely. If the two methods were estimating the same population
size the comparisons in Table 2 should be equal or nearly so.
The population estimates for rainbow and brown trout were pooled, and
the non-parametric signed rank test (Snedecor and Cochran, 1972) showed the
difference between the within week and between week population estimates
was significantly different (p < .01).

TABLE 1. Example of how within week and between week population estimates
were formed, Big Horn River near Thermopolis, Wyoming.

Mark Run
Nov. 17
Nov. 17
Nov. 17
Nov. 18
Nov. 18
Nov. 19
Dec. 1
Dec. 1
Dec. 2

Within Week Estimates
Recap. Run M C R N
-
Nov. 18 235 134 5 5192
Nov. 19 235 226 8 5952
Nov. 20 235 160 6 5428
Nov. 19 131 226 3 7491
Nov. 20 131 160 1 10626
Nov. 20 226 160 5 6091
Dec. 2 159 219 5 5866
Dec. 3 159 272 9 4368
Dec. 3 219 272 8 6673
-
Mean within week estimate 6409
Between Week Estimates
Recap. Run M C R N
- -
Dec. 1 235 159 6 5394
Dec. 2 235 219 9 5769
Dec. 3 235 272 5 10738
Dec. 1 131 159 1 10560
Dec. 2 131 219 4 5808
Dec. 3 131 272 8 4004
Dec. 1 226 159 9 3632
Dec. 2 226 219 4 9988
Dec. 3 226 272 7 7746
Dec. 1 160 159 6 3680
Dec. 3 160 272 3 10988
Mean between week estimate 6947

Mark Run
Nov. 17
Nov. 17
Nov. 17
Nov. 18
Nov. 18
Nov. 18
Nov. 19
Nov. 19
Nov. 19
Nov. 20
Nov. 20

Sample Dates: November 17, 18, 19, 20; December 1, 2, 3, 1981
Species and Size: Rainbow Trout> 7.4"

;J.4