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

cross (Figure 3), involves mating 5 males with 5 females of a stock as
broodstock founders to produce 25 family lots (Kapuscinski et al. 1993).
The entire genetic contribution from mating 5 males and 5 females are
represented in the diagonal cells (upper left to lower right). The
remaining 20 crosses are various combinations of the 10 parental
genotypes.
' Pedigreed matings of this nature (a single uniquely-marked male mated
with a single uniquely-marked female) ensure that every possible genotype
is produced and each parent is genetically represented in the next
generation, thus preserving allelic diversity in the offspring of the
captive stock (Kapuscinski et al. 1993). The mating of ten unrelated
parents in the illustration of a di-allele cross (Figure 3) will maintain
the genetic contributions of all parents. Note the genetic diversity in
offspring from full-sib (Al X Al) or half-sib (Al X A2) crosses. The
resulting offspring of the full-sib cross is illustrated in the lower
left diagram and the half-sib cross is illustrated in the lower center
' diagram. A rather detailed explanation of the di-allele cross
accompanies Figure 3 to explain its use in maintaining genetic diversity.
If space is limited for propagation of all family lots from a 5 X 5 di-
allele cross, maintaining separate groups of the 5 unique family lots
represented in the diagonal cells as illustrated in Figure 3 would be
preferred to maintaining the 20 other matings because these 5 family lots
contain the entire genetic contribution from the 10 parents.
If adult fish are extremely rare and five fish of each sex cannot be
' obtained, factorial matings (Kapuscinski et al. 1993) will be used to
increase the genetic contribution from the least numerous sex (See Item 4
in Box 10).
' After a broodstock has been developed from a 5 X 5 cross or a factorial
mating, additional wild endangered fish should be used to supplement the
genetic contribution of the parent stock until a minimum effective
' populations size of 50 is achieved, providing that no adverse affect will
occur to the wild stock (See Item 5 in Box 10). Additional lots from
mating one male with one female should replace the half-sib lots in the
' di-allele cross to maximize the genetic contribution from the wild
parents.
In some situations, it may be feasible to spawn wild fish at the site of
capture and return them to the habitat from where they were collected.
However, in most situations, fish will be captured, transported to
holding facilities at genetic refuges or hatcheries, and held until they
' can be spawned. The stress of capture and transporting may prevent
potential broodstock from spawning during the year of capture. Even if
fish spawn in the year of capture or a subsequent year, the wild adults
' may be retained at the refuge or hatchery for an additional year to
ensure that F, progeny survive from the initial spawning.
VI. GUIDELINES FOR DISPOSITION OF CAPTIVE-REARED ENDANGERED FISH
A. Background. Many propagation activities may produce more fish than are
needed to meet specified requirements. This additional production allows
' the hatchery manager to compensate for unknown or unpredictable attrition
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