7739

• UCREFRP Catalog Number: 7739
• Author: Muth, R. T. and T. P. Nesler.
• Title: Associations Among Flow and Temperature Regimes and Spawning Periods and Abundance of Young of Selected Fishes, Lower Yampa River, Colorado, 1980-1984 - Final Report.
• USFW Year: 1993.
• USFW - Doc Type: \
• Copyright Material: NO

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15

taxa between and within the native and nonnative groups (Figure 5). In each year except 1981, native
fishes staned spawning earlier than nonnative species; in 1981, red shiner and fathead minnow started
spawning earlier than all native fishes except Dannelmouth sucker. In each year, all nonnatives except
redside shiner ended spawning later than native fishes. Spawning for both native and nonnative fishes
among years staned and ended earliest in 1981 and staned and ended latest in 1983. Among native fishes
in each year, Oannelmouth sucker staned spawning earliest, foUowed closely by Gila sp., speckled dace, and
bluehead sucker, respectively. Speckled dace ended spawning latest, followed by bluehead sucker, GilD sp.,
and Dannelmouth sucker, respectively. For nonnatives, fathead minnow staned spawning earliest, followed
by red shiner, redside shiner, and sand shiner, respectively in aU years except 1981. Sand shiner
ended spawning latest, followed by red shiner, fathead minnow, and redside shiner, respectively. In 1981,
sand shiner staned spawning earlier than redside shiner.
Correlations among years between values of SPAWN-l and SPAWN-T by taxon were different
between the native and nonnative groups (Figure 5). For all nonnative fishes, values of SPA WN-l were
smallest in 1981 and greatest in 1984 and especially 1983, and values of SPA WN-T were smallest in 1983 or
1984 and, except for redside shiner, greatest in 1981. Coefficients for correlations between these
spawning-period parameters, for all nonnatives except redside shiner, were negative and significant (positive
and moderate for redside shiner). Values of SPAWN-l and SPAWN-T for each native taxon were similar
among years, the greatest difference among years occurring in 1981 with values of SPAWN-I, and
correlations were positive for Gila sp. and flannelmouth sucker and negative for speckled dace and
bluehead sucker; however, correlations were weak for all four fishes.

Relative abundana.-Values of total (over all reaches) relative abundance from the two indices, i.e.,
catch-per-unit-effort (CPUE) and percentage of occurrence (PO), were positively correlated among years
for each age class of all fishes except fathead minnow (Table 6). Correlations were strong or significant for
age-O speckled dace, bluehead sucker, red shiner, and sand shiner and for both age classes of redside
shiner.

Variations in total relative abundance of age-O fish among years and relative abundance among
reaches over all years differed mostly between the native and nonnative groups (Tables 7, 8). For all native
fishes except Gila sp., values of total CPUE and PO were greatest in 1984 (greatest in 1981 for Gila sp.),
whereas, for all nonnatives except fathead minnow, these values were greatest in 1981 (CPUE and PO for
fathead minnow were highest in 1982 and 1984, respectively). Smallest values of total CPUE and PO
occurred in 1984 for Gila sp., 1982 for speckled dace, 1981 for blue head and Dannelmouth suckers, 1984
for all nonnatives except fathead minnow, and 1983 for fathead minnow. Among reaches, CPUE for native
fishes was highest over aU years in reaches 1-3 and lowest in reaches 4 or 5. CPUE for red shiner was