Editing Trout (section)

== Declines in native trout populations ==
Salmonid populations in general have been declining due to numerous factors, including [[invasive species]], hybridization, wildfires, and climate change. Native salmonid fish in the western and southwestern United States are threatened by non-native species that were introduced decades ago. Non-native salmonids were introduced to enrich recreational fishing;<ref>{{Cite journal|last=Quist|first=Michael|date=2004|title=Bioinvasive species and the preservation of cutthroat trout in the western United States: ecological, social, and economic issues|journal=Environmental Science & Policy|volume=7|issue=4|pages=303–313|doi=10.1016/j.envsci.2004.05.003|bibcode=2004ESPol...7..303Q }}</ref> however, they quickly started outcompeting and displacing native salmonids upon their arrival. Non-native, invasive species are quick to adapt to their new environment and learn to outcompete any native species, making them a force the native salmon and trout have to reckon with. Not only do the non-native fish drive the native fish to occupy new niches, but they also try to hybridize with them, contaminating the native gene construction. As more hybrids between native and non-native fish are formed, the lineage of the pure fish is continuously being contaminated by other species and soon may no longer represent the sole native species. The [[Rio Grande cutthroat trout]] (''Oncorhynchus clarki virginalis'') are susceptible to hybridization with other salmonids such as [[rainbow trout]] (''Oncorhynchus mykiss'') and yield a new "[[cutbow]]" trout, which is a contamination of both lineages’ genes. One solution to this issue is implemented by [[New Mexico Department of Game and Fish]] [[fish hatchery|hatcheries]]: stock only sterile fish in river streams. Hatcheries serve as a reservoir of fish for recreational activities but growing and stocking non-sterile fish would worsen the hybridization issue on a quicker, more magnified time scale. By stocking sterile fish, the native salmonids can't share genes with the non-native hatchery fish, thus, preventing further gene contamination of the native trout in New Mexico. Fire is also a factor in deteriorating [[Gila trout]] (''Oncorhynchus gilae'') populations because of the ash and soot that can enter streams following fires.<ref>{{Cite web|url=http://www.wildlife.state.nm.us/fishing/native-new-mexico-fish/gila-trout-recovery-angling/|title=Gila Trout Recovery and Angling|website=New Mexico Department of Game and Fish|access-date=Dec 2, 2019}}</ref> The ash lowers water quality, making it more difficult for the Gila trout to survive. In some New Mexico streams, the native Gila trout will be evacuated from streams that are threatened by nearby fires and be reintroduced after the threat is resolved.

[[Climate change]] is also dwindling native salmonid populations. [[Global warming]] continually affects various cold-water fish such as trout, especially as inland waterbodies are more prone to warming than oceans. With an increase of temperature along with changes in spawning river flow, an abundance of trout species are affected negatively. In the past, a mere {{Convert|8|F-change}} increase was predicted to eliminate half of the native [[brook trout]] in the Southern [[Appalachian Mountains]].<ref>{{Cite book|title=Climate Change and Cold Water Fish|publisher=United States Environmental Protection Agency|year=1999}}</ref> Trout generally prefer streams with colder water ({{cvt|50|-|60|F|disp=or}}) to spawn and thrive, but raising water temperatures are altering this ecosystem and further deteriorate native populations.