8121

• UCREFRP Catalog Number: 8121
• Author: Williamson, J. H. and R. S. Wydoski.
• Title: Genetics Management Guidelines.
• USFW Year: 1994.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

effective population size will be accompanied by excessive loss of
genetic heterozygosity. This is especially true if the absolute size of
the wild population is small. Ryman and Laikre (1991) strongly recommend
that the risk of losing genetic variability through captive breeding
should be carefully considered even if only a single stocking is to be
made. Precautions that will be taken during propagation and stocking are
summarized by priority in Box 8.
Box 8. Precautions to be taken during propagation and when stocking
endangered fish into the Upper Colorado River Basin. These
precautions are in priority order.
1. Precautions must be taken to prevent escapement of endangered fish
from refugia or captive propagation facilities.
2. Stocking of captive-reared endangered fish will be conducted only
in locations of the upper basin where it can be demonstrated that
such stocking will not adversely and significantly affect any
indigenous fish populations or stocks of the same or different
species.
3. Supplemental stocking (i.e., experimental, augmentation, and
restoration stocking) will be restricted to locations with suitable
habitat that will support a viable population or stock, or to
historic habitats.
4. All captive-reared endangered fish will be marked before initial
release and stocked as equal family lots from pedigreed matings
so that an adequate evaluation of stocking can be made.
5. Large-scale augmentation or restoration stocking will be done only
when knowledge of life history and ecological requirements of the
target endangered species is known sufficiently well to predict the
likelihood of stocking success.
6. Any proposed stocking of endangered Colorado River fishes will be
described in a stocking plan that is approved by the Program and
is covered by a Federal Fish and Wildlife Permit or a supplemental
permit.
H.
trrective Population Size in Captive Propagation of Endangered Fish. The
effective population size (Ne) is a key parameter in conservation of
genetic diversity because the rate of inbreeding and the loss of genetic
heterozygosity is proportional to the inverse of the effective population
size (Ryman and Laikre 1991). The effective population size can be
calculated using the following formula (Lande and Barrowclough 1987):
N - 0 (males) X 4N (females)
e N (males) + N (females)
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