7858

• UCREFRP Catalog Number: 7858
• Author: U.S. Fish and Wildlife Service.
• Title: Draft Greenback Cutthroat Trout Recovery Plan.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: NO

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1 At present, nineteen populations (including both historic and restoration
populations) are believed to be stable self-sustaining populations (See
definition in Part II), but only two of these stable populations occur in the
Arkansas River drainage. The "historic" populations are located in the higher
elevations of the species' historic range, probably because of less habitat
disturbance and less accessibility to humans than occurred in the lower
elevations.
Reasons for Decline
Fate of historic novulations. Four cutthroat trout subspecies are known to
' have existed in Colorado when European settlers first arrived: greenback
cutthroat trout, yellowfin cutthroat trout, Rio Grande cutthroat trout, and
the Colorado River cutthroat trout. The yellowfin cutthroat occurred in the
upper Arkansas River drainage in Twin Lakes, the Rio Grande cutthroat occurred
in the Rio Grande drainage, and the Colorado River cutthroat occurred in the
Colorado River drainage. Unfortunately, all four cutthroat trout subspecies
proved quite susceptible to negative influences associated with 19th century
development of Colorado. Land and water exploitation, mining, logging and
unregulated fishing all took their toll in reducing the numbers and habitat of
.endemic trout populations. However, no action had more long-term impacts on
the endemic trout subspecies than the introduction of non-native salmonids
which hybridized and competed with native fishes. Shortly after the turn of
' the century, greenbacks had declined to a point that Greene (1937) believed
them to be extinct.
The fate of the greenback population native to Twin Lakes, in the Lake Creek
drainage, illustrates the effects of subsistence harvest and stocking of
nonnative fish, and typifies the response of the greenback trout in general.
According to Behnke (1979), "Twin Lakes was noted for its abundance of
greenback trout in the nineteenth century. In the 1890's rainbow trout, brook
trout, lake trout (Salvelinus namavcush), and Atlantic salmon were introduced.
When Juday sampled Twin Lakes in 1902-1903, rainbow trout were dominant (Juday
1906). Although Juday collected specimens of greenback trout (some of these
were identified as hybrids when examining Juday's specimens at the National
Museum), he found no "yellowfin" cutthroat trout. The greenback disappeared
from Twin Lakes shortly thereafter. Twin Lakes is now primarily noted for its
lake trout fishery."
1 Introduction of non-native fish. The major factor in the decline of the
greenback cutthroat trout was the introduction of non-native salmonid species
(rainbow trout, brook trout, brown trout and Yellowstone cutthroat trout),
within the South Platte and Arkansas River drainages.
The 1800's began with the greenback cutthroat as the dominant salmonid of
these two drainages. However, the arrival of the railroad and the emergence
of fish culture combined to make large numbers of fish eggs and fry readily
available and transportable in a relatively short period of time. The
greenback's failure to respond to early fish culture practices soon led to
other fish species, such as brook trout and rainbow trout, being reared and
stocked throughout the greenback's limited native range.
Hvbridization. Greenbacks hybridize readily with rainbow trout and other
subspecies of cutthroat. Several hybridized populations known to occur in
Colorado are shown in Table 5.
' ,Competition
Brook Trout. The ability of brook trout to displace a pure greenback
population was dramatically demonstrated by events in Black Hollow Creek,
Arapaho/Roosevelt National Forest. Brook trout were removed from this small
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