9428

• UCREFRP Catalog Number: 9428
• Author: Erdahl, D. A.
• Title: Inland Salmonid Broodstock Management Handbook.
• USFW Year: no dat
• USFW - Doc Type: Bozeman.
• Copyright Material: NO

order to insure this number, management plans must
allow for annual mortality, fish health sampling
mortality, and a certain percentage that are not
expected to contribute because they are either
immature, barren, or deformed. To insure a genetic
contribution from 250 paired coatings, 450-500 pairs
of broodfish should be retained.
D. Equal Contribution From Each Mating
It is important that each paired mating contributes
an equal number of offspring to the-next generation.
An equal contribution from individual paired coatings
decreases the variance in genetic contribution from
each mating. Although the number of eggs available
from each mating will obviously vary, an equal
number of eggs from each should be retained for
future brood. For example, if one paired mating
results in 5000 eggs and another in only 1000, the
same number of eggs from each mating should be
retained.
A practical methodology to obtain an equal genetic
contribution from each paired mating is to simply
remove a "spoonful" of eggs from each mating. If
the spoon is perforated with small holes, it will
allow for a more rapid, accurate removal of a
similar number of eggs from each mating. The total
number of eggs obtained using this methodology is of
course directly related to the size of the spoon.
In most cases, a spoon size that results in the
collection of about 50-100 eggs from each paired
mating should provide adequate egg numbers (a
minimum of 250 paired coatings x 50 eggs/mating =
12,500 eggs).
E. Relative Contribution from Each Take
In addition to the fact that each paired mating
should contribute an equal number of offspring to
the following generation, it is also important that
the number of eggs retained from each egg take is
proportional to the total number of females ripe on
that date. In other words, egg takes that involve a
large number of females should contribute a
proportionately greater number of offspring to
future brood populations than egg takes in which a
lesser number of females are involved. In most
cases, accurate assessment of the percentage of
females spawned on a given day will not be possible
until the entire population has completed spawning.
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