The diagram delineates the comprehensive life cycle of the salmon, tracing its development from the egg stage to full maturity as an adult fish.
Notably, the salmon’s life cycle encompasses five distinct stages, with significant variations in both duration and habitat requirements throughout its progression.
Initially, the cycle begins with the spawning of eggs in the upper river grounds, a process that typically lasts between 2 to 3 months. Following this, the alevin stage emerges, wherein the fish, characterized by their attached egg sacs, develops over the next 1 to 2 months in the same freshwater environment. As growth continues, the salmon enter the fry stage, reaching a size of approximately 5 cm, and reside in the lower river for a duration of 2 to 4 years, during which they absorb the yolk sacs.
Subsequently, the salmon transition into the smolt stage, where they adapt to saline environments and grow to about 15 cm in length. This phase can extend from 1 to 8 years in the open sea. Ultimately, mature adult salmon, measuring between 70 to 85 cm, return to the upper river spawning grounds after spending 1 to 5 years in the ocean. It is at this final stage that reproduction occurs, thereby perpetuating the life cycle