8121 - Laserfiche WebLink

Home Browse Search

Box 10. Recommended strategies to maximize the effective population size in the captive propagation of endangered Colorado River fishes. These recommendations are in priority order. Mate one male with one female as a minimally accepted protocol if wild adults are available until an effective population size of 50 is achieved to maximize the genetic contribution from the wild stock and to reduce the rate of inbreeding. 2. Breed as many adults as feasible in a given year until an effective population size of 50 is reached by mating one male with one female. If 25 families cannot be obtained during one spawning season, continue in the following years until 25 paired matings have been attained. It is important that all 50 fish used in the matings are different individuals so that all family lots are unique. If numbers of adult endangered fish are low, use the 5 X 5 breeding matrix or di-allele cross to develop a broodstock (Figure 3). The half-sib family lots provide a safeguard against the potential catastrophic loss of the genetic contribution from any parents. n 1 4. When wild fish are extremely rare and represented by unequal sexes, use factorial matings to capture the genetic contribution from all fish of the least numerous sex. For example, if three males and one female were available, three family lots should be produced by mating all three males with the single female. This example will result in three half-sib family lots. 5. Additional wild adults should be obtained to supplement the genetic contribution from the wild stock for broodstocks developed from the di-allele cross or factorial cross. Where facilities are limited, family lots from mating one male with one female should replace half- sib family lots to maximize the genetic contribution from the wild stock. captive propagation may be necessary to augment wild stocks since a critical level of abundance of adults or threshold density (Allee Effect) may be needed for successful natural spawning (Lande 1988). In river reaches where the endangered fish have been extirpated, restoration stocking will be necessary, provided that suitable habitat is available for all life stages. If an effective population size of 50 adults cannot be obtained in one year, broodstock development can be accomplished over a number of years by mating one male with one female (Item 2 in Box 10). J. Breeding Strategy for Captive Propagation when Small Numbers of Endangered Fish are Available. If the number of available adult wild fish is low, mating 5 males and 5 females using a 5 X 5 breeding matrix (Figure 3) is reasonable (Item 3 in Box 10). Biology Committee participants and an Ad Hoc panel of fishery geneticists agreed that the 5 X 5 breeding matrix should be used as the basic minimal breeding strategy model for propagation of the endangered Colorado River fishes when the number of wild adults is limited. This model, the di-allele 27