Life Cycle

Most salmon are anadromous. In the wild, spawning, fertilization and hatching of roe, and an initial growth period occur in rivers. This is followed by migration to sea and the main growth period, and later, as mature fish, migration back up the river to reproduce. This cycle is duplicated in culture conditions. Mature Atlantic salmon are stripped for roe (eggs) and milt (secretion containing the sperm), these are mixed to allow fertilization, and then the eggs are hatched, all in fresh water. The alevin (young fish) lives off its yolk sac until it has developed enough to be able to consume exogenous feed. Growth continues in freshwater tanks until the fish has undergone a physiological transformation, smoltification, allowing it to survive the hyperosmotic conditions of salt water. With artificial light regimes and good husbandry, the smoltification process may be started early so that smolt are produced during the first autumn, although usually this process occurs later and the fish are not transferred to sea cages until the second spring. Atlantic salmon grow to a market size of 3 to 5 kg during a period of about 9 12 months in the sea. Fish chosen for

□ United Kingdom

■ Norway

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Fig. 1 World production of Atlantic salmon, in thousands of tons (round weight). (From Ref. 1.) (View this art in color at www.dekker.com.)

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Fig. 1 World production of Atlantic salmon, in thousands of tons (round weight). (From Ref. 1.) (View this art in color at www.dekker.com.)

broodstock are moved back to fresh or brackish water a few months before spawning.

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