9425

• UCREFRP Catalog Number: 9425
• Author: Bezzerides, N. and K. Bestgen.
• Title: Status Review of Roundtail Chub
• USFW Year: 2002.
• Copyright Material: NO

1
needed for overwinter survival (Kaeding and Osmundson 1988, Haines et al. 1998).
Larvae hatched in warm tributary streams may die from cold shock as they enter cold,
tion (Ber
d
bl
ry
a
e to pre
mainstem channels, or they may become lethargic and vulnera
1988, Robinson et al. 1998a). Swimming performance of larval and juvenile CRB fish
may be reduced by cold water temperatures, potentially lowering foraging efficiency and

' the ability to escape predators (Berry and Pimentel 1985, Childs and Clarkson 1996,
Robinson et al. I998a, Clarkson and Childs 2000). For adult fish, cold water
temperatures may slow growth and reduce fecundity, further decreasing chances for
re roductive success cAda and Wydoski 1983, 1985, Kaeding and psmundson 1988,
P (M
' Clarkson and Childs 2000, Robinson and Childs 2002).
In addition to temperature alterations, reservoirs capture sediment, and discharge
sediment-poor water downstream (Collier et al. 199b). Alteration of the magnitude and
' timing of discharge, along with capture of sediment in reservoirs, typically results in
downstream increases in water clarity and bank and chancel scour (Collier et al. 1996).
' Reductions in transport of fine sediment may also alter downstream geomorphic
characteristics and availability of spawning sites and rearing habitat (Valdez and Ryel
' 1995, Van Steeter and Pitlick 1998, Douglas and Douglas 2000). Changes in discharge
timing and magnitude may shift environmental cues needed by fish for proper timing of
' migration and spawning, thereby Preventing successful reproduction (Muth et al. 2000).
Lastly, dams, irrigation diversions, and canals entrain drifting larvae and Prevent up- and
downstream movement of all age classes to historical spawning, rearing, and
overvvintering habitat (Martinez et al. 1994, Burdick 1995, Anderson 199'1}. Habitat
' fragmentation is particularly problematic for species that exhibit long-distance migratory
behaviors, such as Colorado pikeminnow (Tyus 1990, Irving and Modde 2000).

Biotic impacts-In addition to changes in the physical environment, humans
have also changed the biotic environment of the CRB. At least 60 non-native fish species
have been purposefully or accidentally introduced in the CRB (Carlson and Muth 1989,
Minckley 1991, Martinez et al. 1994, Valdez and Carothers 1998). Non-native fishes

Final Report September 2002