INCUBATION:
Once the salmon eggs are fertilized, they are placed on trays in amounts of
8,000 per tray. Then they are placed into the incubator, which will be their
life support system for the next 50 to 100 days. During the incubation process, the
salmon eggs will grow into Alevins. Through time the Alevins will exhaust their
yolk sac. This is the point in which the fish is removed from the Heath system
and put into a holding tank. These fish are now referred to as "fry"
and will be hand-fed until they are released. In hatcheries salmon are most
often fed vitamin-rich, high protein diets made up of: dried meals from coarse
fish, animal meat excess, plant meal and bone meal, or meal from calcium-rich
shells.
Important note: the incubation period can be sped up by the
raise in the temperature of the water. This process can also be slowed down by
lowering the temperature of the water.
GEOGRAPHIC PLACEMENT:
Is there any geographic strategy for the placement of a fish hatchery? The
answer to this question is yes, because there is a number of things which must
be considered before locating a site. The most important thing is having a good
water supply that is free of disease. Some examples of good water supplies would
be at the bottom of a dam or at a natural spring, because of the water's
consistent temperature and because most springs are free from disease. Something
to also think about is if the water supply has a chance to freeze, because if
this were to happen the hatchery fish would die from lack of water. Geographic
setting is very important to the survival of the hatchery fish.
Atlantic Salmon Life Cycle
Wild
Atlantic salmon vary in appearance during their lifetime. Until the early 19th
century the life cycle was not understood and documented, and Parr and Smolt
were assumed to be different species of fish.
EGGS
Pea-sized orange eggs are deposited in riverbed gravel in autumn, and hatch the
following early spring. As the eggs develop, the eyes of the developing wild
salmon can be seen through the semi-transparent membrane.
ALEVIN
The partly transparent alevin hatch and remain hidden in the riverbed gravels,
feeding from the attached yolk sac. They are about 2 cm or less than 1 inch in
length.
FRY
Wriggling up from the gravels, fry begin feeding on microscopic life in the
stream. They eventually reach a length of 5 to 8 cm./2 to 3in. before
transforming into parr.
PARR
The vertical markings, called 'parr marks' appear, with a single red dot
between. Parr remain in the river for 2 to 6 years, depending on water
temperatures and food availability.
SMOLT
At a length of 12 to 24 cm/4.7 to 9.5 in. a springtime transformation
of the parr takes place into smolt. A silvery sheen replaces the parr marks, and
internally they undergo a complex transformation to survive in saltwater. On the
downstream journey the odours of the smolt's native river are imprinted on its
memory, to be recalled when it returns to spawn.
ADULT - Silvery hunters, adult wild
salmon live one or more years at sea. Most populations follow lengthy migration
routes to waters off south western Greenland where they grow rapidly on a diet of
crustaceans and small fish. Other feeding grounds exist, such as waters
surrounding the Faeroe Islands north of Scotland, and some populations may stay
closer to home rivers. Wild
salmon that return after one year at sea are called GRILSE.
Adult salmon return to home rivers, entering freshwater between April and
November. Once in freshwater they stop feeding, living off accumulated fat
reserves.
SPAWNING IN A REDD
In late November to December the wild Atlantic salmon spawn. The female digs a
10-30cm/4-12 in. deep nest called a REDD in the gravel bottom of the stream. Her
eggs and the milt from an adult male are released into the redd, the gravel
replaced with additional tail thrusts. In some cases sexually mature male parr
manage to fertilize a percentage of the eggs. In the life cycle diagram parr are seen
swimming nearby, looking for an opportunity. The female may lay 1,500 eggs or
more for each kg./2.2 lb of body weight. - Thus a 12 pound female salmon will
lay about 8,000 eggs, completing the life cycle.
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