Frontcountry Fishery Inventories at Least Three Size/Age Groups Have Consistently Been Caught
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Frontcountry Fishery Inventories at least three size/age groups have consistently MAHONY been caught. Average size of captured trout DAN / was typically between 160 and 175 mm; few NPS individuals were longer than 300 mm (Figure 13). Although the cutthroat trout in Soda Butte Creek have been protected from harvest since 1996, with the adoption of total catch-and- release regulations, few fish longer than 330 mm have been caught in recent years. Comparison of population length structure prior to 1996 with the most recent five-year sampling period Yellowstone cutthroat trout from Soda Butte Creek. suggests that the trout’s response to the catch- and-release regulation in this stream has been Soda Butte Creek Long-term minimal. Similar findings for rainbow trout Monitoring were found in Great Smoky Mountains National Park and suggested that factors other than angler oda Butte Creek has historically been harvest (particularly, stream productivity) might sampled regularly in the park. Since the be most important in regulating fish populations mid-1960s, park fishery personnel have (Kulp and Moore 2005). Estimated abundance S of cutthroat trout in Soda Butte Creek has collected information about the resident fish and macroinvertebrates there to monitor responses, increased since 2002, but most of the increase if any, to reduction in water quality arising from appears to be occurring in younger age classes ongoing inputs of mining-associated pollutants. that were previously not affected by the allowable With few exceptions, annual monitoring has harvest regulation. occurred at a site near the park’s northeast A shift in stream channel location further boundary since 1984. confounds interpretation of long-term Cutthroat trout abundance in Soda Butte population responses in Soda Butte Creek. Creek has varied considerably from year to Downcutting, and the creation of a new stream year, and length-frequency data suggest that channel after the record-high stream flows in 1997, resulted in the loss of approximately half of the old monitoring section. The new channel has undercut numerous trees that have been MAHONY incorporated into the stream. This large woody DAN / debris appears to be a preferred habitat of young NPS cutthroat trout during the colonization of the new stream channel area. Although non-native brook trout had previously been known to reside in the headwater portions of Soda Butte Creek (Shuler 1995), they were not found in the park until 2003. Montana Fish, Wildlife and Parks chemically removed the source population of brook trout from a small upstream tributary in 2004, and re-treated it again in 2005. Although suppression by electrofishing within the park since 2003 has yielded brook trout each year (Figure 13), evidence of a widespread, robust population is lacking. The upstream chemical removal project appears to have reduced the Fisheries crew electrofishing Soda Butte Creek in 2005. brook trout population to where only an 24 occasional individual is now found in the park. Monitoring Associated with Road Cutthroat trout collected during brook Reconstruction trout electrofishing suppression were sampled for genetics analysis. Initial results indicate that Because large sections of many park roads the cutthroat trout have been recently hybridized were intentionally located adjacent to stream with rainbow trout (Olson 2005). In 2005, corridors, road reconstruction projects can NPS biologists also collected fin clips from 40 potentially impact fish populations. In 2005, cutthroat trout upstream from Icebox Canyon we continued to monitor these activities. Most to obtain the current genetic status of the of the projects were at the mid-construction population there. Although these fish have not or completion phase; thus, monitoring was yet been analyzed, at least one had the physical restricted to areas sampled in previous years. In appearance of a hybrid. 2005, electrofishing surveys were conducted at several sites in Hayden Valley, in the tributary of Cascade Creek at the south end of the Canyon-to-Chittenden road, and at three sites 6 40 2001 in Antelope Creek. As in previous years, few 30 4 of the captured cutthroat trout were longer 20 2 than 250 mm, suggesting that the streams are 10 used primarily as spawning and rearing areas 0 0 for fish from the Yellowstone River mainstem. Sampling at 6 However, in Antelope Creek, consistent capture 40 2002 the two sites of 30 4 of multiple size-groups and the presence of 20 potential barriers indicate that the population Middle Creek 2 may be comprised of fluvial residents. 10 on the east side 0 0 Sampling at the two sites of Middle Creek on the east side of Sylvan Pass again revealed 6 of Sylvan Pass 40 a predominance of brook trout over cutthroat 2003 30 4 trout. Relative abundance of both species again revealed a 20 was smaller in 2005 than on other sampling 2 predominance of 10 occasions, but this may have been due, in part, Number Caught 0 0 to reduced capture efficiencies associated with brook trout over 6 the difficulty of sampling during higher stream cutthroat trout. 40 2004 flows. This year, in consultation with NPS 30 4 20 2 joann 10 0 0 vo I GT 6 40 2005 30 4 20 2 10 0 0 50 100 150 200 250 300 350 400 Total Length (mm) Figure 13. Number of Yellowstone cutthroat trout and brook trout captured in the Northeast Entrance sample section of Soda Butte Creek, 2001–2005. Solid bars denote 10-mm length groups for cutthroat trout. Triangular markers denote number of brook trout Non-native brook trout are being removed from upper captured by length group and year. Soda Butte Creek by electrofishing each year. 25 geologists and Federal Highway Administration most monitoring efforts have been focused at staff, Aquatics Section staff sampled the upper local sites where those types of impacts might portions of Middle Creek as a result of water occur. However, a broader temporal and spatial quality concerns arising from the gravel-washing examination is required for all effects of road operation at the top of the Sylvan Pass divide. projects to be considered (Angermeier et al. In September 2005, sampling of Middle Creek 2004). One long-term effect of upgraded roads near the input source of the fine materials failed is increased access and usage. Wider roads to capture any fish. Additional electrofishing and larger parking areas may lead to increased upstream from the affected area also yielded numbers of anglers at streams that are close to a no fish. This brief initial survey suggests that road, but not close enough to be directly affected the localized area was historically fishless and by the actual construction activities, for instance, remains so today. A more extensive survey of the at Obsidian Creek, where angler use may watershed could reveal the presence of barriers, increase due to improved access to the stream upstream distribution of cutthroat trout in the with an upgraded road or removal of size limits stream, and amount of risk to the cutthroat in 2006. This stream was historically fishless, trout population based on its proximity to but brook trout were stocked there in the early the input source. Intensive water quality and days of the park. As brook trout have a high macroinvertebrate surveys have also been catch rate, Obsidian Creek has an unusual status completed to document the potential impacts as a park stream where children are allowed to One long- of sediment from the gravel-washing operation use bait to catch non-native trout. Four years of (described below). sampling near the Indian Creek campground term effect of Typically, road projects are a concern to area have revealed that small brook trout are upgraded roads resource managers because they can potentially abundant in Obsidian Creek. Population data impact fish populations if excessive sediment is obtained during the pre-construction phase of is increased generated during construction or improperly the Mammoth-to-Norris road project will be access and designed or placed road culverts impede fish useful for examination of longer-term passage after completion of the project. As such, changes. usage. NPS / DAN MAHONY An upper reach of Middle Creek sampled in 2005. The close proximity of Middle Creek to the East Entrance Road is a concern to fisheries biologists. 26 Wilderness Fisheries of the South Fine spotted Overview Map Status of Cutthroat Trout in the cutthroat found Cutthroat found Upper Snake River Not found Creeks Creeks - not sampled Rivers he Snake River watershed is the third Rivers - not sampled Roads largest in Yellowstone National Park. Major Lakes THistorically, Yellowstone cutthroat Yellowstone Park Boundary trout, Snake River finespotted cutthroat trout, and several other native fish species occupied the mainstem river and its tributaries. Much of this basin has not been previously surveyed because of its remote location and difficult access to pre-selected study areas. In 2005, the Aquatics Section continued its native fish inventory of the 0 2 4 6 Snake River in order to describe the distribution Kilometers Miles of cutthroat trout subspecies in the remote 0 0.5 1 2 3 4 headwaters region within the park. A primary Figure 14. The upper Snake River watershed where fishes were sampled by objective of the survey is detection of areas where electrofishing in 2004 and 2005, and Snake River finespotted cutthroat trout were the two cutthroat trout subspecies may coexist. found, Yellowstone cutthroat trout (large spotted) were found (“Cutthroat found” in Equally important is documenting the relative the legend), or none were found. abundance and distribution of other native fishes streams were approximately 1 km apart (Figure and potentially harmful non-native species, 14). Forest Creek watershed was most likely including brown trout, brook trout, and lake historically fishless due to the presence of a large trout in this watershed.