In the autumn, we are treated with a natural wonder, one of earth’s great migrations – the salmon run – when adult salmon return to their natal river to spawn. But what are the salmon up to during the winter?
While spawning, a female salmon uses her tail to clean the gravel of a stream bed and form a depression where she will lay her eggs. This nest is called a redd. Just one female can lay around 2,000 soft orangey eggs, so imagine how many eggs are hidden down in the gravels of the creeks and streams of our area! After spawning, adult salmon die leaving their eggs to develop in the protection of the reeds and gravels.
So while you are sitting beside your warm fire, playing in the snow, or enjoying Christmas celebrations, these eggs remain in the gravel developing an embryo. How does the embryo survive in the cold water? They get their food from the yolk of the egg and oxygen from the water running over the redd. After about one month eyes become visible, after two months the embryo begins to move inside the egg and after three months the embryo hatches from the shell.
The redds and eggs are very sensitive at this time. Not all eggs survive – only one in 10 eggs survive to hatch. So if a female lays 2,000 eggs only about 200 survive. Disturbances such as higher water temperatures, freezing, blockages that cause the stream to dry up, polluted water and silt deposits all destroy eggs. As well there are predators like bigger fish, racoons and ducks that feed on the eggs. Dogs jumping in the water can also hurt the eggs by disturbing the redds and causing silt to develop. While out walking your dog, try to keep them away from the water as this will help the salmon.
For more information, check out this resource from Fisheries and Oceans Canada, ‘Salmon in the Classroom‘.
What happens next in the life of a salmon? Stay tuned to find out.