Monday, May 14, 2012

The Life Cycle of a Salmon

The Life Cycle of a Salmon

The life cycle of all salmon follows a series of stages as it develops from an egg to an adult fish. Each species of salmon has its own 'rules' that determine the length of time each stage has and also when these fish return to the rivers to spawn. Therefore each of the pacific salmon species are unique. The information illustrated below shows the stages each salmon goes through.



During spawning, eggs are deposited by the female in redds (a gravel depression scoured out by the adults with their tails). Milt (sperm) is then deposited from the male salmon to fertilize the eggs and begin a whole new generation. Depending on water temperature eggs will take between 6 to 12 weeks to hatch. The tiny black spots you can see in the photo are the eyes developing. These are what we would call eyed eggs.
Salmon Alevin


Alevin are newly hatched fish. They derive their nourishment from the yolk sac of the egg from which they were born. Nourishment is provided by the yolk sac for several weeks. They stay down in the river gravel until the sac is absorbed. Once the sac has been absorbed the 'fry' begin to emerge from the gravel and swim freely looking for food for the first time.
Salmon Chum Fry


Once an alevin's egg sac is absorbed, the fish has to find food for itself. This stage is called the fry stage. The fry will swim about feeding on tiny invertebrates and on the carcasses of the spawned out adults. Fry instinctively hide, deal with river currents, learn to school together and many other survival skills.
Salmon Smolt


Fry live in fresh water anywhere from just a few days to two years depending on the species. Smolting is a physiological change which when completed enables the fish to live in salt water and not absorb the salt into its blood stream. Once a fish turns into a smolt it is ready to begin its migration down the river and into the ocean where it will spend the next phase of its life.
Adult Coho in Ocean

Ocean Life

During their ocean phase Pacific Salmon are widely distributed over the North Pacific and Bering Sea. Most will have extensive migrations from one to five years (depending on the species). This is where the salmon do most of their growing and gain weight quickly. The Ocean phase is the phase which we know the least about and it seems that the early part of the ocean phase is very important for overall fish survival.
Spawning Salmon


When the adult fish have finished growing in the ocean they then seek out the rivers in which they were born to spawn. The fish undergo physical changes from bright silver to much darker and sometimes boldly coloured mature adults. The energy the fish gained in the ocean is put solely into the production of eggs (females) and milt (males). The mature adults pair up and start the process all over again of making a redd and laying eggs. This is where the cycle ends for one but and begins for another. The Seymour River has several viewing opportunities for salmon such as Coho, Pinks, Chinook and Chum. Visit the hatchery during spawning season - updates will be put on the Home page as we start to see fish spawning in the Seymour River.

Life cycle summary

Fish Life Cycle

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