The Atlantic Salmon- Spawning

by Fly Fisherman

SPAWNING.—The salmon is truly an aristocrat, spending the winters in the sea and the summers in the cooler waters of the North. The spawning migration may start as early as April and continue until August or September. However, the majority migrate to the headwaters of the rivers during June. They usually leave the depths of the sea in April and May and spend some time in the brackish waters of the bay to await a rise in the river which makes the traveling easier. They travel mostly at night, then may rest in the deeper pools for a week or more at a time before continuing their journey. However, if the river happens to rise they may proceed during the day.

Fish that enter the rivers early usually take all summer to journey to the spawning grounds, or they may make the trip in a very few days and remain in the same pool until ready to spawn. However, this rapid migration usually depends on the amount of water in the rivers. If the water is high they can make the trip without too much interference of dams and other obstructions. If the water is low then they usually take a longer time.
The fish that wait until September before making the spawning journey may complete the trip in a very few days, and are nearly exhausted upon arrival because of being so heavy with spawn. The early starters are not heavy with spawn and are in excellent condition for the entire trip.

Unlike the Pacific salmon, the Atlantic salmon do not always die after spawning. In some instances death may follow, but the majority survive to return to the sea unless their span of life has been reached. Most of the salmon return to the sea immediately after spawning, but some may remain in the deep pools of the rivers and migrate to the sea in the spring.
In spite of the short span of life many salmon make the spawning migration two or three times. It is rare that they survive to spawn the fourth time although there are records of their spawning four and five times.
The actual spawning takes place during the latter part of October or early November, depending on the temperature of the water. The fish select a place on the gravel bars where the nest is prepared, which is normally from two to three feet in diameter and is usually made by the female as she moves about the area in a series of undulating movements. The use of the head, body, fins, and tail play quite an important part in clearing the space where the eggs are to be deposited. The male fish usually lies near to chase away any intruding males, although the male fish sometimes assists with the building of the nest. The male fish often have some severe battles during the spawning period and it is not unusual for some of them to retreat after receiving some severe lacerations.

After the area is cleared the gravel which is loosened by the activity of the fish is conveyed by the current and deposited in a small pile just below the cleared area. The eggs are deposited gradually, that is, just a few at a time, and are immediately fertilized by the male fish. The eggs are covered with an adhesive substance—until they become water hardened—which allows particles of sand and bits of gravel to be picked up to add to their weight, which prevent the eggs from being carried beyond the small pile of gravel where they settle to be covered with additional gravel loosened by the spawning fish. If the eggs go beyond this small pile of gravel there is great danger that they will be devoured by trout or other fish that eagerly await them. All of the eggs are not received in this one small pile of gravel—several days are required to complete the spawning and many piles of gravel may be made during the period. The eggs range in size from six to seven millimeters in diameter and a single fish may deposit from 6,000 to 25,000 or more according to the size of the fish.

The eggs remain covered by gravel throughout the winter until hatched sometime during the following spring—usually in April or May. The incubation period .depends upon the temperature of the water and the eggs usually hatch in water from 37 to so degrees. When the baby fish hatch and emerge from their gravel bed they are about three quarters of an inch in length. Their small, transparent bodies are very cumbersome and awkward because of the yolk sac which is attached near the head. This sac furnishes the necessary food until finally absorbed some thirty or forty days later, depending on the temperature of the water. As soon as it is absorbed they leave the nest in search of food.

During the first six months the growth is quite rapid and the baby fish may be two inches long. At the end of the first year the growth may have increased to three or four inches or slightly more. By the end of the third year the length may be from seven to nine inches before the fish migrate to the sea.

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