WSP01392

• File Number: 8240.200.10.B
• Description: UCRBRIP - Riverine Fish Flow Investigations
• Basin: Colorado Mainstem
• Date: 6/1/2000
• Author: CDOW
• Title: Riverine Fish Flow Investigations 2000
• Water Supply Pro - Doc Type: Publication

function of a lack of smaller fish there, instead of a lack oflarger fish on the Colorado River.

Mean lengths between all sites were statistically different at P<O.OOI in 1999.

Duffy in 1999 also had the highest percent of larger roundtail chub with 90% of the

sample 40 cm or larger, a result of very few chub under 40 cm. At Sevens 67% of the chub

were 40 cm or larger, but on the Colorado River only 4% were in over 40 cm (Appendix C

Figure 7,8 and 9). Mean length of round tail chub on the Colorado River was 321 mm and

449 mm and 400 mm for Duffy and Sevens, respectively (Table 4.), and mean lengths

between all sites were statistically different at P<O.OOI in 1999. The smaller mean length on

the Colorado River for Chub is due to a much better representation of smaller sized fish.

Table 4. Mean length for fish >15 cm collected in the Yampa and Colorado Rivers.

MEAN LENGTH IN MM
Sevens Sevens Duffv Duffy 15-Mile
Species/year 1998 1999 1998 1999 1999
BH 342 336 357 382 366
CC 497 448 529 476 433
CP 572 533 670 679 440
CPM 628 610 608 575 573
FM 488 465 459 486 422
NP 383 411 433 518
RTC 380 400 442 449 321
5MB 295 276 278 292
WB 329 375 413 421 374
WF 460 442 475 473 393
WS 359 352 411 406 287

Duffy also had significantly higher mean lengths for most other species including

catfish, carp, white sucker and white-flannel mouth and white-bluehead hybrids, pike and bass

(Table 6). On the Colorado River small white sucker were found primarily in backwater

habitats whereas white sucker over 25 cm were primarily in the main channel (Appendix C

Figure 10 and II). The smallest channel catfish caught on the Yampa River was 30 cm and

34

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