Trout

: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera Oncorhynchus, Salmo and Salvelinus, all of which are members of the subfamily Salmoninae in the family Salmonidae.

Most trout are strictly potamodromous, spending their entire lives exclusively in freshwater lakes, rivers and wetlands and migrating upstream to spawn in the shallow gravel beds of smaller headwater creeks.

The hatched fry and juvenile trout, known as alevin and parr, will stay upstream growing for years before migrating down to larger waterbodies as maturing adults.

The name "trout" is commonly used for many (if not most) species in three of the seven genera in the subfamily Salmoninae: Salmo (Atlantic), Oncorhynchus (Pacific) and Salvelinus (circum-arctic).

Mostly, these colors and patterns form as camouflage, based on the surroundings, and will change as the fish moves to different habitats.

Trout in, or newly returned from the sea, can look very silvery, while the same fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration; it is also possible that in some species, this signifies that they are ready to mate.

In general, trout that are about to breed have extremely intense coloration and can look like an entirely different fish outside of spawning season.

The swim bladder is connected to the esophagus, allowing for gulping or rapid expulsion of air, a condition known as physostome.

Unlike many other physostome fish, trout do not use their bladder as an auxiliary device for oxygen uptake, relying solely on their gills.

As salmonids, trout are coldwater fish that are usually found in cool (50–60 °F or 10–16 °C), clear streams, wetlands and lakes, although many of the species have anadromous populations as well.

[3] Despite severely impacting the distribution and abundance of native Australian fish, such as the climbing galaxias, millions of rainbow and other trout species are released annually from government and private hatcheries.

[clarification needed] Trout generally feed on other fish, and soft-bodied aquatic invertebrates, such as flies, mayflies, caddisflies, stoneflies, mollusks and dragonflies.

[4] Compared to other salmonids, trout are somewhat more bony, but the flesh is generally considered delicious, and the texture is often indistinguishable from that of salmon.

[5] In Mainland China, farm-raised rainbow trout from Qinghai was officially sanctioned to be labeled and sold domestically as salmon, which caused much controversy regarding food safety and consumer rights violation,[6] as raw fish dishes or yusheng using Atlantic salmon are gaining popularity in southern China.

[9] By information from International Game Fish Association (IGFA), the most outstanding records are:[10] 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.

With an increase of temperature along with changes in spawning river flow, an abundance of trout species are effected negatively.

In the past, a mere 8 °F (4.4 °C) increase was predicted to eliminate half of the native brook trout in the Southern Appalachian Mountains.