145 



20 



Hatchery broodstock should represent similar proportions of all life history 

 traits existing in wild or natural stocks with which their progeny may 

 genetically interact. 



Some agencies promote periodic infusion of gametes from wild or natural 

 stocks into hatchery stocks with the expectation that this will keep genetic 

 resources and life history patterns of hatchery stocks similar to those of 

 wild and natural stocks with which they genetically interact. This strategy, 

 however, will be futile if variation in family size is not minimized. To a 

 lesser extent, effectiveness of the strategy also will be reduced if other 

 recommendations for maximizing effective population size, preventing 

 founder effects, and avoiding artificial selection in the hatchery are 

 ignored. Carefully designed monitoring of genetic resources and life 

 history patterns in hatchery and interacting stocks is therefore needed to 

 assess effectiveness of periodic infusions of gametes from wild or natural 

 stocks. 



3.7.3 Fertilization Protocol 



A. MaintaiD high effective population size and low variatioD in 

 family size by using the milt from an individual male to 

 fertilize the eggs of an individual female (Withler 1988). 



B. In cases where effective population size can be increased by 



breeding more than one male per female, use the milt of a 

 different individual male to fertilize each separate subset of 

 eggs from an individual female. 



C. In situations where egg supply is severely limited or male 

 fertility is highly variable, pool the milt from overlapping 

 pairs of males (A and B, B and C, C and D, etc.) and 

 immediately fertilize eggs of individual females (Gharrett 

 and Shirley 1985). 



These recommendations differ from the common practice of pooling milt 

 from several or more males prior to fertilizing a lot of eggs from an 

 equivalent number of females. Pooled milt, however, leads to unequal 

 contribution of gametes from different males due to differences in potency 

 of their milt (Withler 1988). Consequently, effective population size is 

 reduced due to unequal sex ratios, increased variation in family size, and 

 smaller total number of parents. ' 



