The diagram illustrates the life cycle of salmon, a large fish species, from the egg stage to maturity.
Overall, the process consists of three main stages occurring in distinct environments: the upper rivers, the lower rivers, and the open sea, spanning a total period of approximately 10 years.
Initially, salmon eggs are laid in the upper reaches of slow-moving rivers, where they are positioned among reeds and small stones. After approximately 5-6 months, the eggs hatch into young fish known as fry, which measure 3-8 centimeters in length.
Subsequently, the fry migrate downstream to fast-flowing lower rivers, where they develop further over a period of approximately 4 years. During this stage, they transform into smolt, a transitional phase in which they reach lengths of 12-15 centimeters. Once mature enough, the smolt leaves its current habitat and moves to the open sea.
The final stage of the salmon’s life cycle takes place in the open ocean, where they live and grow for about 5 years, eventually reaching their full adult size of 70-76 centimeters. At this stage, the adult salmon migrate back to the upper river to reproduce and lay eggs, thus completing the life cycle.