9360

• UCREFRP Catalog Number: 9360
• Author: Bundy, J. M. and K. R. Bestgen.
• Title: Evaluation of the Interagency Standardized Monitoring program Sampling Technique in Backwaters of the Colorado River in the Grand Valley, Colorado.
• USFW Year: 2001.
• USFW - Doc Type: Fort. Collins.
• Copyright Material: NO

ISMP backwater sampling evaluation
fathead minnow, red shiner, and green sunfish (Table 2). Only a single largemouth bass was
captured in backwater 4, the location where bass were very abundant in autumn 1998.
ISMP performance
The lower effort ISMP technique detected the presence of green sunfish and largemouth
bass in relatively few backwaters compared to the higher effort DMR sampling. The ISMP
sampling technique detected largemouth bass in 14 backwaters where DMR sampling detected
the species in 30 backwaters (7 of 14 in 1997, and 7 of 16 in 1998, Table 3). If we assume that
presence of largemouth bass was estimated without error by DMR sampling (e.g., no bass were
present in the remaining 16 backwaters sampled), ISMP sampling detected the presence of bass
only 47 % of the time. The ISMP sampling failed to detect largemouth bass in the second
sampling effort in backwater 4 (sample 4.1) in 1998, a location where estimated bass abundance
was the second-highest (N = 338) recorded in the entire study.
Green sunfish were detected by ISMP sampling in 23 backwaters but were found in 40
backwaters during DMR sampling (11 of 18 in 1997, and 12 of 22 in 1998). Thus, presence of
green sunfish was detected by ISMP sampling only 58 % of the time.
The logistic regression analysis to determine the relationship between the probability of
detection of largemouth bass as a function of their estimated abundance (density) yielded a
statistically significant effect (p < 0.0001). That relationship had the form:
logit Y= -1.781 + 3.065(largemouth bass density),
(1)
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