Conservation of Rio Grande Fish

Life Span of Rio Grande Cutthroat Trout

Mature Rio Grande Cutthroat Trout live between six and eight years, about average for their species (Spaete, 2006). They are stream spawners, and their average age of sexual maturity is between five and seven years of age, with breeding occurring only once or twice during the lifespan (Spaete, 2006). In general, breeding season is between spring and early summer, with offspring in the 1000 to 2000 range (Spaete, 2006). Environmental factors including temperature and food availability will impact the breeding cycle as well as overall size of the individuals.

Habitat Management for Rio Grande Cutthroat Trout

The Rio Grande Cutthroat Trout is a subspecies of the cutthroat living primarily in the rivers of Colorado and New Mexico. In addition to the Rio Grande itself, the Pecos River and the Canadian River are its native habitats. The Rio Grande Cutthroat Trout thrives when it has access to a diverse geographic zone, because it needs different types of habitat for spawning, for rearing of the spawn, for general adult livelihood, and also for temporary refuge ("Rio Grande Cutthroat Trout Conservation Strategy," 2013).

In general, the species requires "clear, cold, highly oxygenated water," as well as "clean gravel substrates, a network of pools and runs, and an abundance of food," (United States Fish and Wildlife Service, 2014, p. 3). For spawning, the Rio Grande Cutthroat Trout requires clean gravel river bottoms with little to no fine sediment. The trout seek slightly higher water temperatures and lower water velocity for nursery habitats. Upon reaching adulthood, the cutthroat trout will congregate in pools, especially those that offer protective features including covers or "riffles for food production and foraging," ("Rio Grande Cutthroat Trout Conservation Strategy," 2013, p. 9). Their main sources of food include terrestrial and aquatic invertebrates (United States Fish and Wildlife Service, 2014). If refuge is necessary, the Rio Grande Cutthroat Trout will hide in deeper pools, albeit those that are freeze or drought resistant ("Rio Grande Cutthroat Trout Conservation Strategy," 2013, p. 9).

Rio Grand Cutthroat Trout Management

Because the Rio Grande Cutthroat Trout has been listed as a sensitive species, the subspecies has been subject to "catch and release" restrictions (United States Fish and Wildlife Service, 2014). Where "catch and release" restrictions are not in place, the United States Fish and Wildlife Service (2014) places limits (2 per day in New Mexico and 4 per day in Colorado) on catches.

Conservation of Rio Grande Cutthroat Trout

The primary threat to the Rio Grande Cutthroat has been invasive species including other members of the trout and salmonid families. The most notable of the nonnative species that have impacted Rio Grande Cutthroat Trout numbers include rainbow trout, brook trout, brown trout, and Yellowstone trout. These nonnative species compete with the Rio Grande Cutthroat for food, habitat and breeding space. As they belong to the same genus, these fish also interbreed, thereby diluting the original gene pool. The nonnative species most likely to hybridize with the Rio Grande Cutthroat include the rainbow trout and other types of cutthroat trout. The species most likely to prey on the Rio Grande Cutthroat Trout include the brown trout. The Rio Grande Cutthroat Trout is most likely to compete with the brook and brown trout subspecies for food and habitat ("Rio Grande Cutthroat Trout Conservation Strategy," 2013, p. 10).

Although considered a "lesser effect" on the Rio Grande Cutthroat Trout in particular, habitat destruction and diseases such as whirling disease are also known issues affecting the Rio Grande Cutthroat Trout populations (Pritchard & Cowley, 2006; Rinne, n.d.). Habitat destruction had occurred largely from the early 20th century onwards, with logging, mining, the establishment of large swathes of ranchland for livestock grazing, road construction, hydroelectric and other types of dams, stream drying, and water extraction all contributing to declining populations. Overfishing might have contributed to declining populations in some geographic zones. Currently, the Rio Grande Cutthroat Trout is not nearly as widely distributed as it once was throughout its native territory, with the bulk of the species to be found in headwater streams at the highest possible elevations (Pritchard & Cowley, 2006). It has been estimated that the Rio Grande Cutthroat Trout is found in only ten percent of its original territory (Pritchard & Cowley, 2006). Moreover, the territory to which the Rio Grande Cutthroat Trout has been restricted, at high elevations, is susceptible to greater temperature fluctuations than the species can tolerate, and additional threats including frequent forest fires ("Rio Grande Cutthroat Trout Conservation Strategy," 2013). Climate change, including repercussions such as increased rates of "extreme events," have been having an adverse impact on the Rio Grande Cutthroat Trout and threatens their chances for long-term survival ("Rio Grande Cutthroat Trout Conservation Strategy," 2013, p. 13).