The diagram illustrates the life cycle of a spawning fish, showing the different stages of its development from eggs to adulthood.
Overall, the fish undergoes a cyclical seven-stage life cycle, beginning with eggs laid in freshwater and ending with spawning adults that reproduce before dying. During this process, it gradually develops through several growth stages and migrates from freshwater to the sea before returning to its birthplace.
Initially, adult fish lay eggs in freshwater, which take approximately three months to hatch. The newly hatched fish, known as alevin, survive by feeding on their yolk sacs for several weeks. They then develop into fry, which are between five and ten weeks old and are capable of swimming independently. After several more months, they reach the parr stage, during which distinctive finger-like markings appear on their bodies.
Subsequently, the fish become smolts at the age of one to three years. At this point, they form groups and migrate to the sea, where they continue to mature. They spend between one and six years in the ocean before reaching full adulthood. Finally, the mature fish return to freshwater to spawn. After laying eggs, they die within two weeks, marking the end of the cycle and the beginning of a new generation.