All species of trout are born in freshwater, even the Sea trout as trout eggs don't develope in salt water. Trout need to lay their eggs in either flowing river water or in the case of Lake trout either in or close to a feeder river or stream leading into the lake. Eggs need a good oxygen rich flow of fresh water to develope and eggs take aproxamitly 30 days or more to hatch into "alevins", depending on the temperture of the water.
Most river Brown trout spawn in early winter usualy November & December, in which they migrate upstream to spawn in the shallow gravel beds in either the river itself or in the small tributries which lead into the river.Alevins are the stage in which the eggs hatch out into tiny embryonic fish that still have their yolk sac attached. At this stage of their life they are still amongst the gravel redd. The term "Redd" is a bed of loose gravel that fish use to spawn. The female digs a trench or pit in the gravel, usualy with her body and tail, she then lays her eggs. At this crutial stage the male trout releases sperm over the eggs and the eggs are then covered over with gravel.
When the alevins yolk sac is used up of it's nutrients they then turn into proper fry. After this stage they come up through the gravel and start to feed.
It isn't long before the fry grow and quickly they look more like a trout. They develope marks down their sides called Parr marks. This is when they are now called "Parr". Dependinig on the amount of food avaible to the fish, they can stay as parr from 1 - 4 years untill they become adult trout. At this stage any sea going varieties of trout develope a silver skin and head down stream eventualy into the sea. These are known as "Smolts". Freshwater trout however who only live in the rivers or lakes take on their adult coloration and don't go through the smolt stage.
Trout can come into breeding condition from the age of 3 years upwards. They then make their way to the spawning sites.
Sea trout and a lot of lake types of trout tend to feed in shoals and then tend to run the river in loose shoals as they make their way towards the gravel breeding grounds. They tend not to either eat at all or very little while they are in the river during the spawning stage.
In a compleatly different contrast, the river trout, who are solitary feeders, remain solitary as they move to the spawning grounds.
Trout choose their mates at the spawning sites and after they have finished spawning the trout are known as "kelts" and they then head back downstream again.
