WSP04463

• File Number: 8460.500
• Description: Platte River Recovery Plan
• Basin: South Platte
• Date: 6/1/1997
• Author: Colo Div of Wildlife
• Title: Inventory and Status of South Platte River Native Fishes in Colorado
• Water Supply Pro - Doc Type: Publication

The combination of different land-use patterns, ljeavy industrialization, extensive water
diversion, vastly changing water quality impacts, and different ecotones included in this hydrounit
precluded combined analysis of all sampling results. The changing conditions are most notable in
the mainstem, but the influence of the tributaries on different river reaches is also very obvious.
In addition to the physical and chemical differences contained throughout this drainage, it spans
many political boundaries. It includes parts of at least eight counties, and three former CDOW
regions. At least four sampling crews have collected information here in the past two years.

For these reasons, this hydrounit was divided into several sections for reporting purposes.
The sub drainages chosen for separate analyses are: the' southeastern tributaries, the western and
northwestern tributaries, the eastern plains tributaries, and the mainstem, which was divided into
three reaches--the reach through Denver and Commerce City from Bear Creek to Henderson in
the Central Region (CDOW watercode 12649), the reach from Henderson to Greeley (CDOW
watercodes 13312 and 13324), and from Greeley to Weldona (near Fort Morgan, mostly CDOW
watercode 13336). These mainstem reaches are presulned to have different properties such as
water quality and quantity impacts, but their designatiqns also correspond to sampling by different
crews, which may introduce an uncertain degree of sampling variability.

The mainstem river from Bear Creek to Henderson was not sampled during 1993 and
1994 when this inventory effort occurred; however, it was sampled using less-intensive methods
in 1995 after analysis for this report had started. The 1995 results are not included in data
summaries in Table 2, but are presented in Table 5 as supplemental information. White sucker,
creek chub, fathead minnow, longnose dace, longnosei sucker, and carp were the predominant
species found, and accounted for 95 percent of the fish collected (Table 5). Green sunfish,
largemouth bass, and yellow perch yielded 4.2 percent, and channel catfish, black bullhead, black
crappie, smallmouth bass, and walleye were found in trace numbers. Introduced species
accounted for 11.5 percent of total collections. Uncommon or sensitive species provided only
five specimens, or 0.3 percent of total collections, which is not surprising given the likelihood of
chronic urban runoff and industrial pollutants entering the river throughout this reach.

The mainstem river from Henderson to the c~nfluence with the Big Thompson River near
Greeley was sampled in the summer and fall of 1994 (Table 6). Sampling conditions varied
widely from day to day. Electrofishing was most eff~ctive near shorelines, snags and other
structure, and backwaters or side channels. Seining iII the main channel worked best when
working with the water flow, but even then, was only marginally effective. Considerable effort
was spent at each site to ensure that a reasonable sample was collected from all habitat types. The
results in Table 7 are believed to reflect an accurate assessment of the relative abundance of actual
populations residing in this reach. However, rare species might be missed, and species which are
difficult to capture by DC electrofishing and seining fn strong current might be underrepresented.

Sand shiner, fathead minnow, and white sucker comprised over 75 percent ofthe total
sample (Table 7), and sand shiners as well as the other shiner species found are probably
underrepresented due to the habitat they occupied (swift, mid-channel habitats). Carp,
largemouth bass, longnose dace, plains topminnow,plains killifish, red shiner, mosquitofish, and

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