7402

• UCREFRP Catalog Number: 7402
• Author: Nesler, T. P.
• Title: Aquatic Nongame Research, Endangered Fishes Investigations.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

Job 2.

Title: Gamefish predation upon endangered fishes

Objective: To determine the incidence of predation by non-native, non-salmonid
gamefish species upon the endangered fishes during the latter's
early life stages.

Gamefish species were collected from seine hauls made during standardized
monitoring surveys for YOY Colorado squawfish on the eolorado River during
September 1987-1988. In 1987, 41 seine hauls were made in 19 backwaters.
Gamefishcollected included 61 largemouth bass, 38 green sunfish (Lepomis
cyanellus), and 6 black crappie (Pomoxis nigromaculatus). In 1988, 45 seine
hauls were made in 20 backwaters. Gamefish collected included 22 largemouth
bass, 82 green sunfish, 4 bluegill (Lepomis macrochirus), 16 channel catfish,
and 90 black bullheads (Icta1urus me1as). The greatest concentrations of
largemouth bass occurred in 1987 in backwaters at RM 175 and l3l.S, comprising
34 and 39 percent, respectively, of the total bass sample. The greatest
concentrations of green sunfish occurred in 1987 at RM 158.6, comprising 55%
of the green sunfish sampled. In 1988, the greatest concentrations of green
sunfish occurred at RM 182.2, 159.3, and 147.2, comprising 11, 17, and 39
percent of the green sunfish sampled. Length frequency distributions of
largemouth bass showed bass ranged from 60-150 rom total length in 1987, and
from 80-170 rom total length in 1988 (Figure 7). Bass numbers peaked in 1987
at 100-110 rom, but no distinct peak was noted in 1988. Green sunfish ranged
in length from 20-130 rom in 1987, and from 20-90 rom in 1988. Green sunfish
numbers peaked at 30-40 rom total length in both 1987 and 1988. The six black
crappie captured in 1987 ranged in length from 80-200 rom total length. Five
of these fish were captured at RM 131.5. The 4 bluegill captured ranged in
length from 40-70 rom total length.
Stomach content analyses of centrarchids in 1987 showed only largemouth
bass had consumed fish prey. Thirty-three of the 58 bass checked (57%) had
either fish species identifiable to some taxonomic level. unidentifiable fish,
or apparent fish remains as part of their stomach contents. Thirty-four prey
fish were observed in 33 bass stomachs. Identifiable fish included 4 fathead
minnows (Pimepha1es prome1as), 2 red shiners (Notropis lutrensis), 1
flannelmouth sucker (Catostomus latipinnis), 4 Gila sp., 4 unknown cyprinids,
and 2 unknown catostomids. Seventeen other fish were also observed but were

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