The diagram illustrates the life cycle of a species of large fish known as the salmon, detailing the stages it undergoes as well as the different environments in which it lives during its development.
Overall, the natural life cycle of the salmon consists of three main stages, beginning with eggs laid in freshwater and ending with adult salmon returning to their birthplace to reproduce. The entire process, lasting around 10 years, occurs across upper rivers, lower rivers, and the open sea.
At the beginning of the process, salmon eggs are laid among reeds and stones in a slow-moving upper river, which offers protection. After 5 to 6 months, they hatch into fry, measuring 3 to 8 cm, which are then carried to faster-flowing lower rivers. There, they live for about 4 years and gradually develop into smolt, reaching 12 to 15 cm.
The process continues when the smolt migrate to the open sea, where they mature into adult salmon over 5 years, growing up to 76 cm. Finally, the adult salmon are instinctively drawn back to the upper river from which they originated, where the cycle is completed as they lay eggs once again.