8173

• UCREFRP Catalog Number: 8173
• Author: Gido, K. B. and D. L. Propst.
• Title: Habitat Use and Association of Native and Nonnative Fish in the San Juan River, New Mexico and Utah.
• USFW Year: n.d.
• USFW - Doc Type: \
• Copyright Material: NO

can cause short-term changes in depth, velocity, substrate, and

cover (Bain et al. 1988; Allan 1995). Over longer periods,

flushing flows may change the morphometry of the river by

aggregation or degregation of sediments and banks (Waters 1995),

which may influence riparian vegetation (Gregory et al. 1991;

Friedman et al. 1996). Conversely, sustained low flows can

result in armored substrata, loss of seasonally ephemeral

habitats, or encroachment of erosion-resistant riparian

vegetation (Friedman et al. 1996).

Baseline information essential for recommending reservoir

release patterns to the benefit of native fish communities should

include habitat-use data on native and nonnative species (Moyle

and Baltz 1985). It is also important to consider the age-

classes of each species to account for ontogenetic shifts in

habitat use (Matthews and Hill 1979; Moyle and Vondracek 1985;

Mullen and Burton 1995). Moreover, an understanding of the

degree of habitat-use overlap among native and nonnative species

must be obtained. These aspects of habitat use are necessary so

that management strategies that focus on creating habitat for a

native species do not inadvertently benefit nonnative species.

Overlap in habitat use does not necessarily indicate

negative interactions among species. Species with high overlap

in habitat use, however, are more likely to compete for

resources. This can be particularly important during "crunch"

periods when key resources are most likely to be limited (Weins

1977). Thus, characterizing these associations is an important

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