7994

• UCREFRP Catalog Number: 7994
• Author: Duff, D. A., Tech. Ed.
• Title: Conservation Assessment For Inland Cutthroat Trout, Distribution, Status and Habitat Management Implications.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

Two planning meetings associated with the assessment were held prior to completion of the ques-
tionnaires. The first meeting involved individuals knowledgeable with the Snake River drainage; the
second meeting involved individuals with specific knowledge of the Yellowstone River drainage. At
these meetings the basic purpose of the assessment was discussed and the questionnaires were
refined. Projected time frames for completion of questionnaires were also identified. In addition to
information derived from the questionnaires, attempts were made to secure and validate historical
information which made reference to occurrence of cutthroat trout.

RESULTS AND DISCUSSION

Several reports have alluded to the current status of Yellowstone cutthroat trout and other native
trauts in the west (Hanzel 1959; Behnke and Zam 1976; Hadley 1984; Thurow at at 1988; Varley and
Gresswe1l1988; Behnke 1979 and 1992). In a number of these appraisals (Behnke 1979 and 1992;
Varley and GressweIl1988), Yellowstone cutthroat trout were viewed as doing surprisingly well when
compared to other cutthroat subspecies. Behnke's (1979 and 1992) assessments were associated
mainly with biomass within Yellowstone National Park and the headwaters of the Yellowstone River
and not to distribution or preservation of diversity. Varley and Gresswell (1988) provided a quasi-
quantitative assessment of current Yellowstone cutthroat trout status (85% occupancy of native lake
environments; 10% occupancy of original stream habitat) but they provided no information on how
the quantification was derived. Nor did they elaborate on how they arrived at their statements related
to success, especially for riverine populations. Thurow et at (1988) provided an assessment of
cutthroat trout status within the Idaho portion of the Snake River drainage but again the assessment
was largely qualitative in nature. Within Montana, Hadley (1984) prepared a status report for Montana
Department of Fish, Wildlife and Parks utilizing Yellowstone cutthroat information available in the
state's computerized database. Hadley's summary assessment projected an 8 percent occupancy
rate for pure strain Yellowstone cutthroat trout in the Yellowstone River drainage.

This status assessment is intended to be an extension of these earlier efforts. Current information is
based on conditions occurring within the entire range of Yellowstone cutthroat, including the finespot-
ted form that occupies a portion of the Snake River drainage. To facilitate reporting and discussion
of the status information, findings will be presented by State and to some extent by National Forest.

Idaho

The assessment area within Idaho included the Snake River drainage from Shoshone Falls upstream
to the border between Idaho and Wyoming. Included within this area was the mainstem Snake River,
the major tributaries and numerous smaller tributary streams. Three National Forests (Sawtooth,
Caribou and Targhee NF's) occur within portions of this area. In total, twenty one (21) sub-basin areas
(Table 1) were established and a questionnaire for each was completed. The mainstem Snake River,
between Shoshone Falls and the confluence of the Henry's Fork and the South Fork of the Snake
(also referred to as the Snake River) was divided into two sub-basin units; one section of stream
between Shoshone Falls and American Falls and another section between American Falls to the
confluence of the Henry's Fork and the South Fork Snake River. In addition, several of the major
tributary drainages, within this section of the Snake River (Goose Creek, Raft River, Bannock Creek,
Portneuf River, Blackfoot River and Willow Creek) were treated as separate analysis units. The
Henry's Fork of the Snake River was divided into a section upstream from the confluence with the
South Fork of the Snake to the town of St. Anthony along with another section extending from St.
Anthony to Henry's Lake. Within this portion of the drainage several major tributaries (Teton River,
Falls River, Warm River, Buffalo River) were identified as separate sub-basins as was the drainage

15