Browsing by Author "Heim, Kurt C."

Now showing 1 - 3 of 3

Arctic grayling (Thymallus arcticus) in saltwater: a response to Blair et al. (2016).
(2016-11) Heim, Kurt C.; Whitman, Matthew S.; Moulton, Lawrence L.
Although not well known, Arctic grayling can move through saline waters and are captured regularly in nearshore coastal waters in Arctic Canada and Alaska with salinities up to 18 ppt. We highlight the implications this has for Blair et al. (2016), a paper recently published in Conservation Physiology.
Attraction, Entrance, and Passage Efficiency of Arctic Grayling, Trout, and Suckers at Denil Fishways in the Big Hole River Basin, Montana
(Wiley, 2022-07) Triano, Ben; Kappenman, Kevin M.; McMahon, Thomas E.; Blank, Matt; Heim, Kurt C.; Parker, Albert E.; Zale, Alexander V.; Platt, Nolan; Plymesser, Katey
The Big Hole River basin in southwestern Montana supports the only indigenous, self-sustaining fluvial population of Arctic Grayling Thymallus arcticus in the conterminous United States, but the basin is fragmented by numerous low-head irrigation diversion dams. Denil fishways at 63 diversion dams provide Arctic Grayling and other fishes opportunities for year-round access to critical habitats; however, their efficiency has not been evaluated. We quantified attraction, entrance, and passage for hatchery-reared Arctic Grayling, wild trout (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta), and wild suckers (White Sucker Catostomus commersonii and Longnose Sucker C. catostomus) during 14 field trials conducted at six Denil fishways over a representative range of fishway slopes and hydraulic conditions using passive integrated transponder telemetry. Attraction (60.4–84.3%) and entrance (44.3–78.6%) efficiencies were variable across test conditions and reduced overall fishway efficiencies (19.1–55.8%). In contrast, upon entry, passage efficiencies were high (96.2–97.0%) for all taxa across all test conditions. Attraction of hatchery-reared Arctic Grayling increased with upstream depth (a surrogate for fishway discharge) and attraction flow, but attraction of wild fish was less affected by these conditions. Entrance of Arctic Grayling, Brook Trout, and Brown Trout decreased with upstream depth and fishway slope, especially when plunging entrance conditions associated with shallow downstream depths were present. However, entrance of Arctic Grayling and both trout species increased with downstream depth, and submerged fishway entrances demonstrated promise for increasing entrance efficiency at fishways with high discharges and steep slopes. We demonstrate that comprehensive evaluations of fishway efficiency components can identify specific solutions that improve fishway efficiency; application of these engineering solutions at individual fishways (as needed) could improve their efficiency and further enhance aquatic connectivity for fishes in the Big Hole River basin and elsewhere.
Leveraging public harvest to reduce invasive hybridization in Yellowstone National Park: field identification and harvest of cutthroat × rainbow trout hybrids
(2020) Heim, Kurt C.; McMahon, Thomas E.; Ertel, Brian D.; Koel, Todd M.
Leveraging public harvest can be a cost-effective invasive species management tool, but target taxa must be correctly identified and removed at rates that achieve biological objectives. We explored the potential role of recreational anglers to curtail expanding hybridization between invasive rainbow trout (Oncorhynchus mykiss; RT) and native Yellowstone cutthroat trout (O. clarkii bouvieri; YCT) in the Lamar River watershed in Yellowstone National Park. We sought to (1) develop a hybrid identification key that could be used by anglers and (2) estimate angler participation, catch, and potential exploitation rates. We assessed seven morphological features of trout in the field (n = 251, 15 locations) and collected fin clips to estimate RT ancestry proportion using genetic analysis. An identification key was built using recursive partitioning to objectively distinguish YCT from RT and hybrids. A single-choice dichotomous key (white pelvic fin tip present/absent) correctly classified 93% of fish as native (YCT) or containing RT ancestry (RT or hybrid). Success increased to 97% when a second criterion was added (head spot count ≥ 6). Using angler surveys (2013–2017), we estimated that 10,000 anglers catch 50,000 trout annually. In a popular road-accessible area, most trout are probably caught and released ~ 5 times each year. The combination of high angler participation, substantial annual catch, and an accurate and easy to use identification method indicate that leveraging public harvest is a promising management tool. Invasive hybridization is a global conservation issue threatening many native taxa; this case study highlights some factors for resource managers to consider prior to implementing public harvest regulations and the benefits of standardized keys to distinguish hybrids in the field.