9585

• UCREFRP Catalog Number: 9585
• Author: U.S. Fish and Wildlife Service.
• Title: Inland Salmonid Broodstock Handbook.
• USFW Year: n.d.
• Copyright Material: NO

Rate of Loss of Genetic Variability
The rate of genetic loss per generation by drift can be defined as:
1
2 (EN)
For Example: EN = 4 The rate of genetic loss/generation = 12.5
EN = 50 The rate of genetic loss/generation = 1.0~
EN = 100 The rate of genetic loss/generation = 0.5~
EN = 250 The rate of genetic loss/generation = 0.2~
The effective population size is inversely related to the rate of
loss of variation by genetic drift.
Founding Broodstocks from Wild or Free Roaming Populations
Considerations for founding broodstocks from free roaming
populations are basically the same as those that apply to captive
broodstocks. If possible, new broodstocks should be founded on a
minimum of 100 paired matings. Wild broodstocks should be founded
over a period of 3 consecutive years, which facilitates obtaining
the required number of paired matings. Management plans should be
developed that allow, for crossing all 3 year classes with one
another as they mature. If possible, gametes should be collected
over the entire course of the spawning season to insure maximum
genetic variation.
Regardless of how a wild broodstock is managed at the hatchery,
unintentional selection will gradually adapt these fish to the
hatchery environment. Improved hatchery performance is not an
indication of potential for improved performance in the wild. In
virtually all situations, it is likely that adaptation to the
hatchery environment will result in decreased potential for
performance in the wild. When electrophoretic analysis and other
baseline data indicate that the variability of wild broodstocks is
being lost due to adaptation to the hatchery environment, infusion
of new genetic material from the original wild population should be
considered.
1-9