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"~ 80 Appendix B. Principal Comments Received On The Whooping Crane Recovery Plan Technical/Agency Draft The Notice of Availability of the Technical/Agency Draft of this Recovery Plan for public review was published in the Federal Reoister on June 10 of 1993. All comments, even those received after the 30-day comment period, were considered. The Service distributed about 60 copies of the Draft Plan and received 13 comment letters. The comments discussed below are a composite of those received. Similar comments are grouped together. Substantive comments which question aspects of the Plan are discussed here. Editorial comments and supportive comments are not discussed. All comments received are on file in the Whooping Crane Coordinator's office, at the Southwest Region regional office of U.S. Fish and Wildlife Service. Time spent by each reviewer and comments provided are appreciated. Comment: The downlisting goal of 40 pairs plus 25 pairs in each of two other populations is not based on scientific estimates of population viability. Response: The downlisting goal in the three populations is based on Samson's (1983. Minimum viable population - A review. Natural Areas J. 3:15-23) estimate of the number of isolated breeding organisms necessary to prevent inbreeding over the short-term. The goal identifies a point at which downlisting could occur if the population size did not drop below that' minimum in the three populations during a decade. However, attaining the 25 pair goal does not mean that recovery efforts would be discontinued. It is hoped that each population will continue to grow because 25 pairs would be insufficient to maintain genetic diversity and to ensure survival of the species long-term. The Service places emphasis on the multiple population goal, believing that a single large population is still highly vulnerable to extinction due to a catastrophic event. These populations can be managed as a meta- population by manipulating the genetic exchange. Population viability is a young science and there are differing theories (estimates) on how many individuals are necessary for population viability. As the science matures there should be better data on population sizes req'uired for species survival. The current downlisting goal is unlikely to be attained before year 2020. If the present rate of growth continues in the AWP, there will be 500 individuals in that population including about 1 50 pairs. There will be opportunities to modify the downlisting goal over the next 27 years if that becomes appropriate as scientific knowledge increases. Comment: There should be down-listing and delisting criteria based on the possibility that the AWP will forever be the only reproducing wild population. Response: The Service, supported by the recovery team, does not agree that downlisting and delisting goals should be established on the assumption that the AWP may be the only self-sustaining population. Real security for the whooping crane as a species will only be possible if several populations can be established. As long as a Single population exists, wintering on a restricted area of the Texas coast, the population remains vulnerable to eradication in the wild due to a contaminant spill along the Gulf Intracoastal Waterway. A very large AWP containing 1,000 individuals might warrant downlisting, but not delisting unless it expands its wintering range over a larger area of the Texas Gulf Coast. In 1988,