E in the Colorado River Basin and are a major predatory threat to four U.S. federally listed species: the Colorado pikeminnow (Ptychocheilus lucius), humpback chub (Gila cypha), razorback sucker (Xyrauchen texanus), and also the bonytail (Gila elegans) [46,47]. Johnson et al. [48] estimated that northern pike consumed extra fish on a per-capita basis than any other fish species in the Yampa River. Control efforts for northern pike are ongoing in the Yampa River, which would benefit from far more facts with regards to sources of recruitment [47,49]. The Yampa River is situated in northwest Colorado and flows mostly towards the west from its headwaters inside the Flat Tops Wilderness to the Green River near the Colorado/Utah border (Figure 1a). Geologic composition PW0787 custom synthesis underlying the Yampa River is diverse (Figure 1b), and this may perhaps be reflected in water chemistry which in the end impacts the chemical composition of fish otoliths [502]. It truly is largely totally free flowing, with intense alterations in flow becoming driven by snowmelt [50]. Flows frequently commence growing in April, with maximum flows in Might and June, then decreasing flows beginning in July. Northern pike had been stocked in Elkhead Reservoir (that is 98 rkm downstream of Lake Catamount in the Yampa River Basin) in 1977 and likely escaped in to the Yampa River from the reservoir within the late 1970s [54]. Subsequently,Fishes 2021, 6, x FOR PEER REVIEW3 ofFishes 2021, six,maximum flows in May perhaps and June, and after that decreasing flows starting in July. Northern 3 of 14 pike have been stocked in Elkhead Reservoir (which is 98 rkm downstream of Lake Catamount inside the Yampa River Basin) in 1977 and most likely escaped into the Yampa River from the reservoir within the late 1970s [54]. Subsequently, they spread throughout the Yampa River as there spread all through spot following the dam therebuilt. no barrier in location right after the dam they was no barrier within the Yampa River as was was However, an outlet screen and spillway net have considering the fact that outletadded to prevent escapementsince been added to stop was built. Nevertheless, an been screen and spillway net have [55]. Two reservoirs within the upper Yampa River have established populations of northern pike: Stagecoach Reservoir escapement [55]. Two reservoirs inside the upper Yampa River have established populations and Lake Catamount. Dam constructionandLake Catamount was completed in 1978Lake of northern pike: Stagecoach Reservoir on Lake Catamount. Dam building on and Stagecoach Reservoir was constructed in 1989. Northern pike were first detected in Catamount was completed in 1978 and Stagecoach Reservoir was constructed in 1989. Stagecoachpike were first detected in Stagecoach Reservoir in 1994, potentially from an Northern Reservoir in 1994, potentially from an illicit introduction, and then in Lake Catamount in 1995, then escapees from Stagecoach Reservoir escapees from Stagecoach illicit introduction, likely as in Lake Catamount in 1995, likely as [49]. Escapement is a lot more NSC405640 Data Sheet probably than[49]. Escapement is for Lake Catamount for the reason that this isfor private reservoir Reservoir illicit introduction much more likely than illicit introduction a Lake Catamount closed to this is a access plus the priority in the lake’s management is a rainbow lake’s due to the fact public private reservoir closed to public access as well as the priority from the trout (Oncorhynchus mykiss) fishery, (Oncorhynchus mykiss) fishery, to which an illicit northern management is a rainbow trout to which an illicit northern pike introduction could be pike introdu.