I love this time of year! In the Copper River of Alaska, the King or Chinook Salmon begin their journey home. We don’t know how or why, but an adult spawner heads back to the place they were born. Once there, they end one cycle and begin another.
This graphic shows the lifecycle of a salmon. The eggs hatch and develop into alevins. The alevins remain under the gravel for three to four months, living off of the yolk sac.
At about 12 weeks, the alevins emerage from the gravel redd to find food for themselves. Called fry at this stage, they are about an inch long and feed on insects. They are also nice snacks for larger fish, birds snakes and frogs. Some species (Pink and Chum) start immediately downstream. Sockeye will hang around for a few months and Coho and Chinook will stay in the stream for several years.
At the next stage, the salmon grown to about two inches long and develop spots and vertical stripes called parr marks and they are called parrs. As they grow longer, they are called fingerlings.
The next stage marks a big change for the salmon. As they reach the estuaries of their home river (the place where the river meets the sea and fresh and salt water mixes) their scales become larger, they turn silvery, their tail lengthens and bcomes more deeply forked. They stay around the estuary undergoing changes to preparing to survive in a saltwater environment. They feed heavily and grow larger to help them survive as they enter the ocean. Finally, they head out to sea.
Once in the ocean, they will continue to feed and grow into adult salmon. Depending on the species, they will remain in the ocean for 1 to 7 years and some travel thousands of miles to reach feeding grounds.
Swimming along in the ocean one day, something “dings” in them and they begin their journey home to their spawning grounds. They will swim across the thousands of miles back to their river. Along the way, they continue to feed heavily storing up body fat for the long trip up the river. When the fish arrives at the mouth of the river, they are at their peak of weight and fat. Once they enter the fresh water, they stop feeding and live on the stored body fat and muscle to get to their spawning ground.
They undergo a number of changes as they continue up the river. As they reach the spawning ground, the female digs a redd with her tail and lays the eggs. The male then fertilizes the eggs. Each adult may spawn in multiple redds before they are “spawned out.”
As the circle closes, the fish die after spawning – sometime living as long as another week. They stay with the redds the bodies of the salmon become food for many small arthropods living in the fresh water. These become the first food source for the baby salmons – in a way, the adult provides for their offspring through their death.
This is an amazing ecosystem created by our God.