Life Cycle of the Salmon

The life cycle of the salmon as explained in the video is an incredible journey that begins in freshwater streams. Female salmon prepare nests, called redds, by cleaning and shaping gravel into shallow indentations. They deposits thousands of eggs in their nests and their mate follows closely behind and fertilizes the eggs. The fresh, cool water helps bring fresh oxygen to the eggs and eventually a fry is born from the egg. They are born with the yolk still attached, which they need for nourishment. At this point they live in the shallow "backwater and stream waters". As they grow to be an inch long they are called fingerlings. Once they are large enough they leave the shallows and move into the deep channels where they use large rocks and wood for safety and shade. Smolting is the next stage as the baby salmon are big enough to travel in schools and they head down river for the migration out to sea. Their bodies start undergoing physiological changes as their environment transitions from freshwater to saltwater. The large school of juvenile salmon pool up in estuaries at the mouth of the river and begin their next stage of life with the outgoing tide into the ocean. Salmon spend between 2 and 5 years at sea where they migrate "around the Pacific Ocean in varying migratory patterns" in search of food. During this time they put on weight until their instincts drive them to locate the stream they were born in, which they can locate by smell. They are driven to make their way upriver to find spawning beds to lay their eggs. Dams pose a real problem for their progress, but fortunately some dams were created with fish ladders to allow fish to pass. At this point fish live only off their fat stores. They have come back to their birth stream and once they lay and fertilize their eggs they begin to die, thus becoming food for insects which will provide food for their offspring.

I find the whole life cycle very intriguing, how salmon morph into sea dwelling fish and return to die in their freshwater birth stream. What I find most amazing is how they can identify the right river by smell. This seems like a really unusual skill, especially for a fish, and it makes me wonder what other creatures have this same instinct.

Salmon have an important place in the food chain. They feed a number of large predators who need the meat to sustain their own population. If the salmon become extinct the whole local food chain may also begin to unravel with unpredictable consequences. A healthy fish population is also a sign of a healthy river system, so if the population becomes extinct, it should make us aware of our own unraveling culture.