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

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reach section described for the fish sampling. Aerial photos were qualitatively used to
compare habitat availability in the surveyed study sites to longer sections of the river.
The images of the sites were rectified using ground control points and the Imagine
software package. These images were then registered in the Surface Modeling Software
(SMS) and were used for reference in creating the finite element mesh.

RESULTS

FISH SAMPLES

Species Composition

Percentages of fish captured by electrofishing, included fish less than 15 cm
(YOY, and smaller species; speckled dace Rhinichthys osculus, mottled sculpin Cottus
bairdi, sand shiners Notropis stramineus, fathead minnows Pimephales prome/as, brook
stickleback Culaeainconstans, redside shiner Richardsonius balteatus and green sunfish
Lepomis cyanellus). This information is given in Appendix I Table AI.l.

White sucker Catostomus commersoni hybrids were common at both stations and
for certain reporting purposes were grouped with those that appeared to be pure white
suckers. The white-cross grouping, referred to as WSWX, represents both apparent
pure white and white sucker hybrids. White sucker hybrids comprised at least 50% of
the WSWX group at both Sevens and Duffy (Table Al.2).

For fish over 15 cm, tlannelmouth sucker Catostomus latipinnis was the most
common species in the Representative Reach (RR) at the Sevens station. Flannelmouth
sucker comprised 43% of the total fish caught but was 37% based on density estimates
(Table 1). In the shorter surveyed site (SS) the most common species were
tlannelmouth sucker and WSWX at 28% each (Table 1). The SS site had more WSWX
than the RR station (17%), but less bluehead sucker Catostomus discobolus (14%) than
the RR station (27%)(Table 1). Roundtail chub Gila robusta and other species had
higher percentages in the SS site. There appeared to be a higher composition of "pool"
associated species in the 55 site and a lower representation ofron (tlannelmouth sucker)
and riffle (bluehead sucker) species in the 5S site than in the longer RR station.

At Duffy Tunnel, WSWX comprised 67% of the fish caught over 15 em (Table
2). WSWX composition was 59% in the RR station based on density estimates,
compared to 63% in the SS sites. Smallmouth bass Micropterus dolomieu composition
was somewhat higher at the SS site 13% than in the longer RR station where it was 11%
(Table 2). Flannelmouth sucker was lower in the SS site (3.9%) than the RR station
(7.4%), while bluehead suckers were very similar between the two IOCl!tions (4.6 % YS.
5.0%). Roundtail chub composition was a little less in the SS site (2.5%) than in the
long RR (3.8%). Species composition was more similar between the SS site and the RR
at Duffy Tunnel than at the Sevens station.

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