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

difficult and inefficient in deep, rapid velocity habitats and
our experience indicated that few fish occupied deep, high
velocity habitats (Gido et al., in press).
The majority of the species and age-classes examined used
low velocity (<0.2 m/s), shallow (<0.4 m) habitats (Table 2) .
Silt was the predominant substrate in most habitats sampled,
while cobble substrata occurred less frequently. Debris was
present in 23.0% of the habitats occupied by fish. Adult E.
osculus and sub-adult ~. discobolus occupied habitats with higher
current velocities than other species. Adult C. lutrensis,
juvenile Ictalurus punctatus, and sub-adult ~. discobolus and ~.
latipinnis commonly occupied habitats with depths >0.35m.
Stepwise discriminant analysis indicated that velocity,
depth, and percent coverage of silt and sand significantly
contributed towards discriminating habitat use between the 20
species and age-classes (Table 5). Current velocity and depth, 1r~
however, were considerably more important than other variables.
The first axis loaded positively on velocity and negatively on
silt, while the second axis contrasted velocity with depth.
Species centroids plotted on the first two axes indicated that
adult age-classes of both native and common nonnative species
used habitats with higher current velocities (Fig. 3). On the F~
second axis, the age-classes of the two common nonnative species
also appeared to use slightly deeper water than the respective
age-class of native species. Although the overall model was
significant, it only classified groups correctly 17.2% of the

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