The illustration shown represents the life cycle of salmon, a large fish species. The process has three phases, each with different conditions and periods of time, within the upper river, lower river and open sea. From one step to another the fish evolves and grows until it becomes an adult salmon, the moment when it reproduces and marks the start of a new cycle.
The first phase starts after an adult salmon deposits its eggs in the upper river, with slow moving tides, near small stones under the reeds. The eggs stay there for approximately five to six months, until they become “fry”, measuring 3 to 8 centimeters long.
After that, these small fishes move to the fast flowing streams of the lower river, where they remain for around 4 years. It is only when they evolve into “smolt”, a bigger salmon with around 12 to 15 centimeters, that they move to the open sea.
It is after approximately five years in the open sea that they achieve the last step of its evolution, the adult salmon, a fish with around 70 to 75 centimeters long. To finalize this cycle, they travel back to the upper river, where they deposit their eggs, and initiate a new life cycle.
In summary, this process is around ten years long and covers three different environments, each with its specifications and the right conditions to make salmons evolve.