The diagrams illustrate the life cycle of a salmon, highlighting its three distinct stages of development across different environments.
Overall, the salmon’s life cycle consists of three main stages: spawning in the upper river, growing in the lower river, and maturing in the open sea before returning to the upper river to reproduce, completing the cycle.
In the first stage, adult salmon lay their eggs in the slow-moving waters of the upper river, typically among gravel and small stones. The eggs remain in this environment for approximately 5 to 6 months before hatching into fry, which are small and measure between 3 and 8 centimeters in length.
The second stage begins as the fry migrate to the fast-flowing waters of the lower river. Here, they grow and develop into smolt, undergoing significant physiological changes. This stage lasts around four years, during which the smolt reach lengths of 12 to 15 centimeters.
In the final stage, the smolt migrate to the open sea, where they mature into adult salmon, growing to sizes of 70 to 76 centimeters. Once fully grown and capable of reproduction, the adult salmon return to the upper river to spawn, thereby completing the life cycle and beginning it anew.