Rainbow trout are native to western North America from the Aleutian Islands to northern Mexico, but have been widely introduced to waters throughout North America and the rest of the world. They were first introduced to New York waters in the 1870s from fish originating in California, then reared in a Caledonia, NY hatchery. Rainbow trout usually spawn in their fourth year, and they may spawn several times during their lives
The life cycle of trout has not changed that much in millions of years before the first trout angler arrived on our planet. All trout species are born in fresh water including the sea going forms. Female trout lay their eggs in a redd ( i.e. a shallow hole that acts as a egg nest) which it makes using its tail fin. The female trout lays its eggs in the redd in quick flowing river or stream water. Slow moving streams and lakes make poor spawning grounds for trout. r. The fertilized eggs are about 4 mm in diameter and dependent upon the trout species will hatch in between 3 to 5 months.As a general rule the warmer the water the quicker the eggs will hatch. However, if the water gets too warm at above 10 to 15 degrees centigrade the water then looses too much dissolved oxygen which can be fatal to the eggs, with the advent of global warming it remains to be seen what effect this will have on future trout populations. The long period of incubation also leaves the eggs somewhat susceptible to predators and disease at this stage in the life cycle of trout. he life of young trout is very dangerous, predators such as kingfishers, herons, otters, and vermin such as mink and cormorants along with other fish including its own species are always a threat to its survival
DNA studies have shown that rainbow trout are closer genetically to Pacific salmon than they are to brown trout.