Carl:

Concerning your first point, you are correct in that our hind sight is 20/20, that unintended consequences have resulted from what originally was good intentions. Yet, that connot explain why state wildlife agencies, now aware of these situations, are continuing to release hatchery rainbow trout of one origin into streams containing a native race of the same species. I suspect that the answer is that the native population is already bastardized so continuing will seemingly not make matters worse.



And it is my current understanding that some agencies are continuing to release non-native Eastern Brook Trout into high elevation lakes in which no native trout existed in the first place.



As to your second point, I understand perfectly. However, when proposals to release herps back to where they have been exterpated, as was the case on a recent threat on the PARC web site, there has been considerable, unreasoned concerns and opposition voiced for such projects even by some professional biologists. Go figure???



And I agree with your third point as well. ("I don't believe these situations (when native population is extinct) can be used as an arguement to justify release of non-native animals into extant populations." But other than the two points mentioned in my original post, from a biolgical perspective, I have never been concerned, one iota, about the release of one or a few specimens of non-native origin into areas containing the same species. This is considerably different from the repeated mass releases of non-native trout over time, a situation that has had the potential of obliterating native trout populations.



Considering the Rubber Boas as an example, releasing one or a few specimens from one region into another region I consider as a non-issue, just as per the Ringneck snake except for the two reasons I mentioned.



My reasons are as follows: The native populations have been selected to survive the specific environmental conditions that exist in their region. Released boas from a region with a different set of environmental conditions are not likely to survive for two reasons. 1. They have to compete without an established home territory in unfamiliar surroundings against a population with established home territories. Secondly, if one or more specific requirements, for survival of the introduced specimens, are not present in the new terrotory, their chances of survival are further diminished.



But for the sake of argument, lets say one or more introduced specimens survive to breed. After dispersal into new surroundings, odds are overwhelming that any introduced specimen will breed with the native boas. Once mature, subsequent hybrids will further mate with native boas and so on. Thus, a steady dilution of the introduced genes will occur by this process. Further dilution of introduced genes will also occur in that genes from the introduced boas that do no promote survival will be selected against in the new environment.



It is likely that 99.99 % of the genes from the introduced and native boa populations are identical. And in very few generation, any non-identical gene alleles from the non-native stock will either be virtually eliminated and those that may have survived would likely be in a heterozygous state and have little to any impact on the native boa population.



Richard F. Hoyer

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