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<br />Arizona Game and Fish Department
<br />Draft EA: Kanab Ambersnail
<br />
<br />June 1998
<br />Page 21
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<br />vegetation to which the egg masses are attached Metacercaria are too small to identify on vegetation
<br />surfaces in the field, Even if a trained technician using a microscope examined the vegetation, the
<br />microscope lamp would bake the egg masses rendering them inviable,
<br />
<br />The risk ofKAS transplant failure is increased by moving the snails from a wild setting to an artificial
<br />one, and then back to the wild, Even ifcaptive-breeding faciJitiesare initially sterile environments,
<br />there is always a risk of containment failure and possible introduction of foreign pathogens/parasites,
<br />For example, in April 1998, aKA WG visit of the NAU facility (housing a 10j-status KAS population)
<br />discovered 12 KASs had escaped from their enclosures, and were within a 2 m proximity of another
<br />mollusk species held on site, This situation raises concerns of security and the potential of
<br />contamination ofKAS breeding stock. Using a propagation facility would also increase the logistical
<br />support required, and may exceed the time frame for current project funding and staff participation,
<br />
<br />Other snails at risk have been successfully reared in captivity with the intent to re-establish wild
<br />populations, These include seven species of Partula, Pacific islands endemics extirpated by the
<br />introduced predaceous snail Euglalldina (Johnson 1991), and the Chittenango ovate ambersnail
<br />(Novisuccinea chittenangoensis), a New York endemic threatened by the introduced pest snail
<br />Succillea sp, B (Breisch 1996), 10 both cases, reproduction in captivity has increased the number of
<br />individuals for release into the wild, but no pest-free establishment sites have been found, These
<br />captive breeding populations were not intended to raise parasite-free stock, rather to boost population
<br />sizes that were being decimated by predation and displacement in the wild, There is little reason to
<br />believe that translocating snails from a wild source to other sites will be any less successful than
<br />efforts to create captive populations, This is especially true when suitable sites are close to the KAS
<br />source atVP, and are biologically and environmentally similar, Furthermore, it has been shown in
<br />numerous species that re-establishment or introduced populations from wild stock, rather than captive
<br />stock, have higher fitness and survival potential (pers, comm, M, Dem/ong),
<br />
<br />There are three general genetic factors affecting persistence of small populations, First is founder size
<br />(Fitzsimmons et ai, 1997), If founder population size is small, founders may carry only a part of the
<br />total genetic variability of the source population due to sampling error. Second, loss of genetic
<br />heterozygosity can affect the short-term success of introduced populations (Leberg 1990) by possibly
<br />reducing population growth, fecundity, and survival rates, An individual is heterozygous for a gene
<br />when it has received a different allele from each parent; heterozygosity decreases as individuals
<br />become more inbred Last, allelic diversity affects the ability of a population to adapt to changing
<br />environments (Lacey 1987) The population may become vulnerable to new predators, diseases,
<br />parasites, climatic conditions, competitors, and changing food supplies
<br />
<br />Viable population size determined from genetic analyses alone should be used only as a rough
<br />estimate of the minimum number of individuals desirable within a population (Reed et al, 1988), For
<br />vertebrates, founding population sizes of 10 or more individuals can retain most (~95 percent) of the
<br />heterozygosity in the source population (Leberg 1990), assuming all individuals survive and
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