The life of a salmon follows a predictable pattern. It begins in the upper reaches of a freshwater river, as a small egg on a gravel bed in the wilderness, typically in the mountains. After a couple of years, the young salmon (known as a smolt) heads downstream and out to sea. When it reaches maturity, one to eight years later, the adult salmon can find its way back to the original stream or river, and uses its powerful sense of smell to locate the tributary where it was born.
After a strenuous swim upstream, the adult salmon breeds, spawns, and generally dies within a week, creating a nutrient-rich environment for the infant salmon that are about to hatch. And so the cycle begins again.
Imprinted at an early age:
- Experiments in the 1950s found that young smolts are particularly sensitive to the unique chemical odors of their home turf.
- Swimming upstream is difficult work, and only the strongest complete the journey and spawn the next generation of salmon.
- The annual salmon run is a major event for grizzly bears, bald eagles, and sport fishermen.