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Bert Cushing - January 11, 2010


I am from Pennsylvania.

As you know, many freestone streams suffer from excessive thermal problems during the summer and subsequently, few stocked trout survive unless they are able to find cooler waters. My questions center whether it is possible to produce a more thermal tolerant trout. In PA, our fish commission suffers from declining revenues and increasing costs. I am not a biologist but know that it is possible to genetically choose the traits one wishes for in many plants and animals. Is this possible to achieve with trout? Do you know of any attempts to select these properties?

My second question deals with a possible strain of rainbow trout that may already be thermal tolerant. A few years ago (5-10) I believe I read an article about "desert" trout that were able to survive higher temperatures. I do not know what state they were located. If in fact these trout exist, would it be possible for the various state agencies to collaborate and bring a "brood" stack back to PA and begin to propogate a more thermal tolerant trout?

I am sure you can see the ramifications. I find it hard to believe professional fish biologists have not thought about this or attempted this in the past. Your thoughts are welcomed.

Thank you for your time.  Sincerely, Doug Steltzer



Thanks for the questions. However, because your concerns are more fish biology than stream ecology, I asked for some help from a couple of colleagues more familiar with thermal relations for trout. Here’s what each sent me:

Bob Behnke (Professor Emeritus, Colorado State Univ.): There are populations of rainbow and cutthroat trout that evolved under unusual thermal regimes and have hereditary bases for functioning at high thermal tolerance. I've called these thermally tolerant rainbow trout, "desert redband" trout. I discussed some of this in my 1992 work, Native Trout of Western N. Am. (AFS monograph 6), see pgs. 24, 41-43. Also, the section on redband trout in my 2002 book, "About Trout" repeats some of my 1992 comments. Trout are a coldwater fish. Selective breeding can't do much to change this. I doubt that any species of tilapia can be selectively bred to become a coldwater fish.

Chris Kennedy (USFWS Fisheries Biologist): 1) I don't see why this couldn't be done. If there are wild populations that have shown that they are more tolerant to higher temperatures they could be brought into a hatchery and propagated and stocked.

2) I am not aware of any work that has been done on upper temperatures, but there has been work like this for lower temperatures.

3) It's a possibility, but it's doubtful that they could be transplanted from a desert environment and do well in the waters of Pa.

I hope this helps, Doug.  There is a bit of ambiguity in the two responses, but this is the best I could come up with.


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