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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

EXECUTIVE SUMMARY

A three-year field inventory of front-range and eastern plains fishes in streams in the South
Platte River basin has been completed. Over 800 sites were visited in 15 hydrographic units (stream
drainages) and 47 percent of the sites contained fish. The sample of more than 62,000 fish
demonstrated native species comprised over 95 percent. Twenty-five of27 native species expected
to occur in these South Platte streams were found, and 60 percent of these species were found to be
abundant .or common. Of the native species, 6 were judged to be abundant, 9 common, and 10
uncommon. Of 16 introduced fish species found, only one was considered common, the remainder
were uncommon and reproductive success by introduced fish was insignificant overall. Five to six
of the uncommon fish species are being considered as the focus of intensive conservation management
actions, which may include state listing as threatened or endangered. Native species diversity on a
per site basis has declined since 1980, though on a larger watershed or sub-basin scale, native fish
species diversity and the distribution of native fish communities appears better than expected. At
present, introduced fish species is not considered a limiting factor in the welfare of these South Platte
native fishes. Large scale habitat modification within the flow regime, water quality, and river channel
morphology have occurred from historic times, and are more likely contributing factors to the
declines observed in distribution and abundance of some of the native fishes.

F our species assemblages were identified from cluster analyses and categorized by
macrohabitat types. The presence/absence of native fishes was compared to 22 habitat parameters
using stepwise regression analyses, Microhabitat selection was evident among species occupying the
macrohabitat type. The number of native fish species per hydrographic unit ranged from 3-18 and
10 hydrographic units contained 10 or more native fish species. The frequency of occurrence of
native fish communities across hydrounits indicated none of the four categories described here appear
rare or at risk. The uncommon native fishes represent the missing components in most of the fish
communities in each hydrographic unit. The greatest numbers of nonnative fish species were
associated with hydrographic units supporting high numbers of native fish species.

Management and research recommendations include:

1. intensive conservation emphasis directed toward those native fish species observed to be in
decline and extremely rare in abundance or limited in distribution. These efforts would
include further inventory to better document occurrence, distribution and abundance of
populations of six species in or adjacent to known occurrence sites.

2. translocation of individuals to establish new populations in unoccupied stream habitat or pond
refugia.

3. enhance regulatory protection via extended restrictions in potential take or harvest, and
consideration of listing as threatened or endangered via the Commission process.

4. continue monitoring of 3 fish species of special concern vulnerable to decline.

ix