9313

• UCREFRP Catalog Number: 9313
• Author: Burdick, B. D., J. Flair, M. Lloyd and B. Scheer.
• Title: Native and Nonnative Fish Use of Two Gravel-Pit Ponds Connected to the Upper Colorado River at 29-5/8 Road Near Grand Junction, Colorado.
• USFW Year: 1997.
• USFW - Doc Type: Project number CAP-6-GP,
• Copyright Material: NO

Figure 6). Densities (F/10m2) for the five most common fishes collected in
Gardner Pond were: black crappie (6.2), black bullhead (5.1), largemouth bass
(23), western mosquitofish (1.2), and green sunfish (0.4). For Hotspot Pond,
largemouth bass (2.0), western mosquitofish (2.1), black crappie (1.2), green
sunfish (0.4), and black bullhead (0.1; Table 5).
Size Structure of Common Fishes
Length-frequency histograms were plotted for four nonnative fishes
collected in each pond: largemouth bass, black bullhead, black crappie, and
western mosquitofish. The length-frequency distributions for the first three
species represent young-of-the-year fish whereas the length-frequency histogram
for western mosquitofish represents young-of-the year as well as sub-adult and
adult age groups. The size distribution for largemouth bass was similar for both
ponds (Appendix E; Figure E.1.). The mean TL was 61 mm (34-99 mm) and 63 mm (37-
95 mm) for largemouth bass from Gardner and Hotspot ponds, respectively. Most
of the young-of-the-year black bullhead were collected from Gardner Pond. The
mean TL was 37 mm (26-53 mm; Appendix; Table E.2.). It was difficult to
distinguish age groups for western mosquitofish, although it was apparent that
they had reproduced in 1996. The mean TL for all age groups of western
mosquitofish collected in Gardner and Hotspot ponds was 34 mm (21-47 mm) and 36
mm (15-56 mm), respectively (Appendix; Table E.3.).
A bimodal, length-frequency distribution for black crappie suggested that
this species could have spawned twice in both ponds during 1996 (Appendix E;
Table E.4.). Another possibility was that the second bimodal peak (60-69 mm TL)
represents Age-1 fish. The mean back-calculated length data for black crappie
produced in ponds and reservoirs in northwestern Colorado at annulus I was 76 mm
(Personal communication, Patrick Martinez). The same pattern for black crappie
was observed for both ponds. The two modal length classes for Gardner Pond were
20-29 mm and 50-59 mm whereas the two length classes for Hotspot Pond were 30-39
mm and 60-69 mm. This indicated that spawning may have occurred in Hotspot Pond
before Gardner Pond. Hotspot Pond is shallower than Gardner Pond and water
temperatures probably warmed sooner and faster in Hotspot allowing fish to spawn
earlier and grow more rapidly.
CONCLUSIONS
The following were conclusions from the research of this study:
1. The species composition of both ponds was predominantly nonnative
during three sampling periods that coincided with pre-runoff, runoff,
and post-runoff of the Colorado River.
2. Native fishes used the two connected ponds mostly during runoff.
3. Five species of sub-adult and adult nonnative fishes moved between the
two ponds that were connected to the river. White sucker and
largemouth bass migrated the most between the two ponds. Roundtail
chub was the only native fish to move between the two ponds.
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