A member of the family Salmonidae, trout is the common name for many species, as well as being part of the name for certain non-salmonid fish, such as the spotted seatrout or speckled trout.
Lake trout and also most other types of trout live in freshwater lakes and rivers exclusively, although there are others, such as the steelhead trout, which can spend up to three years at sea, before they return to freshwater to spawn; a habit which is more commonly found in salmon. Steelhead that live their entire lives in fresh water are widely called rainbow trout. Also, arctic char and brook trout are part of the char family. They are and have always been, an essential source of food for both humans and wildlife, including brown bears and certain birds of prey, such as eagles. They have been categorised as a health giving oily fish.
Trout which come from different environments, typically have drastically different patterns and colours from other trout. Mostly, the colours and patterns work as camouflage, which are based on the trout’s surroundings, and can change as the fi
sh moves to different habitats. Trout which are currently in, or have recently returned from, the sea, tend to have a very silvery look, while the same fish living in an alpine lake or small stream, could have wildly different colours or more pronounced markings. It is also speculated that in certain species of trout, colour markings signify that they are ready to mate, with trout having extremely intense colours, in general, when they are ready to mate.
Trout fins are entirely without spines, with all of them having a small adipose fin along the back.
The pelvic fins sit far back on the body. The swim bladder in a trout is connected to the oesophagus, which allows for gulping or for rapid expulsion of air. Unlike many fish with similar anatomies, trout do not use their bladder as an auxiliary oxygen update device, instead, relying entirely on their gills.
Many species are isolated from each other and have become morphologically different. Since many of the distinct populations show little to no genetic differences, there may be many different species of trout, when really they all exist as the same species.
