WSP04979

• File Number: 8240.200.10.B
• Description: UCRBRIP - Riverine Fish Flow Investigations
• Basin: Colorado Mainstem
• Date: 6/1/1999
• Author: CDOW
• Title: Riverine Fish Flow Investigations 1999
• Water Supply Pro - Doc Type: Publication

INVERTEBRATES

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As with the RR sections, mean lengths for most species were larger (6 of 11) at
Duffy SS than at Sevens SS (Table 7). At Duffy the SS had similar mean lengths for all
taxa to the RR except for the most common species, white suckers (Table 7), In contrast
there was a strong tendency for smaller fish at the Sevens in the SS than the RR. Mean
length was significantly smaller for 6 of 11 taxa in the Sevens SS (Table 7).

Table 7. Tests of mean lengths offish between the four study areas: Duffy RR,
Duffy SS, Sevens RR and Sevens SS. Alpha equal 0.05.

RR SS DUFFY SEVENS
DUFFY Vs. Sevens DUFFY Vs. Sevens RRVs. RRVs.
Species SS SS
DB S.D.' S.D..' ad. 'ad
CC S.D.' ad n.d S.D.'
CP S.D." ad n.d. ad.
CPM ad - n.d. n.d.
FM S.D." n.d ad S.D."
NP S.D." S.D.' ad S.D."
RTC S.D." S.D.' n.d S.D.
5MB n.d S.D.' n.d n.d
WB S.D.' n.d n,d. n.d,
WF S.D." S.D.' n,d S.D.'
WS S.D.' S.D.' S.D.' S.D.'

SO' Significant for 2 tail test (95%)
SO" significant for 1 tail test (95%)

Enumeration of samples collected by date and station is given in Appendix 2.
Density was higher at Duffy than at Cross Mountain ranch on all dates. Diversity was
higher at Duffy except during October (Table 8). The greatest density was in September
at Cross Mountain, and in October at Duffy (Table 8). October samples I, 2, 3 and 4 at
Cross Mountain and 1 and 2 at Duffy were from areas recently re-watered following an
increase in flow (Figure 2). The flow on September 3 was 209 cfs. Minimum flow was
113 cfs on September 11 and flow increased to 394 cfs by October 8, when the final
sample was taken. The reduced density of these samples was apparently related to the
fact that shallow areas were recently dry.

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