8123

• UCREFRP Catalog Number: 8123
• Author: Wydoski, R. S.
• Title: Coordinated Hatchery Facility Plan
• USFW Year: 1994.
• USFW - Doc Type: Need for Captive-Reared Endangered Fish and Propagation Facilities.
• Copyright Material: NO

f
The importance of maintaining detailed and accurate propagation records
for captive broodstocks cannot be overemphasized. Records should include
the origin, genetic profile, and unique identifying number of each adult
broodfish as well as its production record and progeny performance.
C. Estimating the Number of Fish Required to Produce Broodstocks. The
number of endangered fish needed at the end of each growing season to
produce broodstocks is dependent upon the attrition (i.e., mortality)
rates of the fish at the end of each growing season. Conservative
attrition rates were estimated by consensus among members of the
Propagation Subcommittee and Biology Committee. These attrition rates
will be refined from empirical data from captive propagation of the fish
in different facilities. Estimates of razorback suckers or Colorado
squawfish needed at the end of each growing season until the fish mature
and can be maintained as broodstocks in a primary and a backup refuge are
provided in Figure 3. To be certain that about 30 adults (preferably
equal sexes) from each family lot are available as broodstocks in primary
and backup refuges, the numbers of fish required at the end of each
growing season is estimated to be: 1 - 500 fish; 2 - 250 fish; 3 - 200
fish; 4 - 160 fish; 5 - 152 fish; and 6 - 144 fish.
As experience is gained in effective culture of the endangered Colorado
River fishes, the numbers of fish required to develop broodstocks may be
reduced and would require fewer resources (i.e., space for propagation,
personnel, funding, etc.). Therefore, a scenario involving fewer fish
per family lot as broodstocks may be selected depending upon the
objectives of the stocking plan. Since mortality of fish during the
first year of culture may be highly variable, the focus should be on
estimating the number of adult fish that can reasonably be expected to
survive from the number of fish at the end of the first growing season
from the following scenarios:
Age 1/ Num er o endangered is at the en
of each growing season 2/
Fert. Egg 5,000 4,000 3,000 2,000 1,000
' 1 500 400 300 200 100
2 250 200 150 100 50
3 200 160 120 80 40
4 160 128 96 64 32
5 152 122 91 61 30
6 144 116 87 58 28
1/ The age refers to the end of each growing season.
2/ Estimated attrition rates are: fertilized eggs 90%; between 1st
and 2nd growing season - 50%; between 2nd and 3rd - 20%; between
3rd and 4th - 20%; after 4th - 5%.
The Gila species will mature after four growing seasons when they
are about 14 inches in total length based on estimates of growth
for the Upper Colorado River Basin. It is entirely possible that
growth will be much better in ponds and the fish would reach a
29