9585

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

SECTION 1. GENETICS
Enhancement and perpetuation of the resource is the common goal of
all fisheries management programs. Genetic considerations are
vital to this goal because fish are a product of their genes, the
environment, and of the interaction between the two. The genetic
characteristics of a given fish population, in concert with the
environment, determine the quality and longevity of the fishery
resource. Unlike the goals of commercial aquaculture which select
for optimum performance in the hatchery environment, fish reared
for rehabilitation or restoration purposes must perform in the
wild. Fisheries managers must realize that the implementation of
many "standard hatchery practices" affect the genetic make-up of
fish stocks and impact the potential for survival and performance
in the wild. It should always be remembered that one cannot select
for traits in the hatchery that will insure performance in the
wild.
Traditionally, fisheries managers have concentrated on the
manipulation of non-genetic parameters to alter~or "improve" the
quality of their product. This approach has allowed for
inadvertent changes in the genetic make-up of fish stocks. Long-
term management implications related to these genetic changes have
not been considered. The disregard for the genetic make-up of fish
stocks is extremely unfortunate as relatively minor changes in
management practices may result in substantial impacts on the
genetic integrity of fish stocks. Management activities that do
not reflect consideration-for genetic impact can result in changes
in the genetic integrity of stocks that may prove difficult if not
impossible to rectify.
Evolutionary geneticists have long been aware that genetic
variation is an important aspect of the genetic make-up of managed
fish stocks. The long-term utility of genetic variation is that it
allows fish populations to adapt to changing environmental
conditions. The genetic diversity of a population is a finite
resource that with improper management can be lost. Kincaid, 1976
(1), found that the loss of genetic variation in rainbow trout
reduces hatching success, growth, survival, and disease resistance.
He found that a 25~ reduction in heterozygosity resulted in a 38~
increase in morphological deformities, a 19~ decrease in fry
survival, and a 23~ reduction in weight gain after 364 days.
During the past several decades, broodstocks have inadvertently
undergone intense genetic selection and manipulation. Despite the
best of intentions, management practices have been conducted with
little or no understanding of genetic principles and potential
genetic ramifications. As a result, a significant portion of the
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