The diagram illustrates the life cycle of a species of large fish known as the salmon, highlighting its different growth stages and the habitats it occupies.
The life cycle begins in the upper river, where salmon lay their eggs among reeds and small stones in slow-moving water. These eggs take approximately 3 to 6 months to hatch into fry, which measure between 3 and 8 cm in length. Once hatched, the fry migrate to the lower river, where the water flows faster. They remain in this environment for about 4 years, growing into smolt with a body length ranging from 12 to 15 cm.
After reaching the smolt stage, they travel to the open sea, where they spend around 5 years maturing into adult salmon. At this stage, their size significantly increases to 70–76 cm. Once fully developed, the adult salmon return to their original spawning grounds in the upper river to reproduce, thereby completing the cycle.
Overall, the life cycle of salmon involves three main stages: fry, smolt, and adult salmon. Each stage takes place in a different aquatic environment, ensuring their growth and survival before they return to their birthplace to lay eggs.