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use of the Nucleus I concept an inefficient strategy for 

 conservation of gene diversity. 



3. Small captive populations can be effective for some 

 conservation goals but are not appropriate for long-term 

 retention of gene diversity. 



4. Regional taxon advisory groups developing regional 

 collection plans should not rely on a single "blanket" 

 strategy (e.g., 90% gene diversity/100 years) for all captive 

 breeding programs, but rather, use a number of different 

 strategies based on the most effective use of captive space 

 for species conservation." 



In our verbal testimony before the Committee, AFA suggested that 

 1,000 individuals was more realistic than 50 to 75 as the minimum captive 

 population size necessary to maintain genetic diversity. The basis for this 

 number comes from the 1995 National Research Council (NRC) report on 

 Science and the Endangered Species Act, pages 8 and 9: 



"If the members of the population do not mate with each other 

 at random (the case for most natural populations), then the 

 effect of small size on loss of genetic variation is made more 

 severe; the population is said to have a smaller effective size 

 than its true size. Populations with long-term mean sizes 

 greater than approximately 1,000 breeding adults can be viewed 

 as genetically secure; any further increase in size would be 

 unlikely to increase the amount of adaptive variation in a 

 population. If the effective population size is substantially 

 smaller than actual population size, this conclusion can translate 

 into a goal for survival for many species of maintaining 

 populations with more than a thousand mature individuals per 

 generation, perhaps several thousand in some cases. An 

 appropriate, specific estimate of the number of individuals 

 needed for long—term survival of any particular population 

 must be based on knowledge of the population's breeding 

 structure and ecology. If information on that species is lacking, 

 information about a related species might be useful." 



The key point we wish to make is not that the minimum population 

 size should be 1,000 instead of 50, but rather that the use of blanket numbers 

 like these should be avoided in the regulations. Such requirements can lead 

 to unexpected foreclosures of future conservation options. However, AFA 

 recognizes that a much better job of genetic management can be accomplished 

 than is presently the case, and that much can be done with less than optimum 

 population sizes, or less than desired numbers of new founders in the form of 

 wild-caught exotic birds. One key to reducing the need for new wild-caught 



