Trout Life Cycle

	Egg – Once egg is fertilized, the egg begins to develop and various organs such as eyes become visible. Depending on temperature, it takes 6 to 8 weeks from fertilization to hatch.
	Egg-sac alevin – At this stage, the young fish has hatched from the egg but remains protected within the gravel bed while it retains its egg sac and relies on yolk for nutrition.
	Fry – Once the egg yolk has been absorbed, the young fish emerges from the gravel to become a free swimming fry, reliant on external sources for nutrition. Young fish are generally considered fry during their first year. Fingerling – This term refers to a particular size of fish approximately 3-4 inches in length. Hatchery managers often refer to this size for stocking purposes.
	Parr – This term refers to young fish during the freshwater period from the time they enter their second growth season to the time they transform to the smolt stage. Parr are characterized by “parr bars” or a series of parallel vertical markings along their sides. Smolt – Immediately prior to emigration from the natal stream, juvenile fish undergo a physiological, behavioural and physical transformation, enabling them to adapt to the new environment in which they will rear to adulthood. In the case of anandromous species, this transition occurs from coastal streams/lakes to saltwater. For purely freshwater forms and species, this transition occurs from small natal stream to larger river or lake. Smolts lose parr markings and take on a very silvery colouration.
	Adult – Salmonids generally spend one or more years feeding and growing either in saltwater or in larger river/lake systems prior to returning to their natal stream to spawn. The exception is resident fish (including some rainbow trout, cutthroat trout and other salmonids) which do not leave their natal system prior to spawning. Fish that undergo migration to larger systems can generally access greater food resources and therefore grow larger than resident-type populations.
	Spawning adult - Upon maturation, fish undergo a series of physiological, behavioural and physical changes to ready them for spawning. The most obvious physical changes are colour – from silver to distinct spawning colours (usually brightly coloured) - and morphology (particularly males) associated with competition for mates and nest-building.