the diagram illustrated the life cycle of the salmon. Probably this circulations have shared by several stage.
At the first, from the egg salmon started at fresh water about 5 month before tranformated to alevin. After that alevin must feeds by several weeks to continue as fry. Definetly fry already can be swimming at this circulations but still stay in the fresh water before going to sea water. The process of swiping fry to parr is already and takes several monthly old and also develop a fingers.
On the other hand, next step is adapting parr into smolt before fresh water became sea water. this part salmon has already to life at sea ecosystem and more independent action to carry on adult and also takes time 8 years adapting this habit and then move to spawning adult.
However, the circulation of the salmon shows about several stage start from the egg then petite move to last spawning adult and also transmigring habit from fresh water into sea water, at the end, this illustrations will have turning around for next step
