Here is the reply from the good professor. Way above my head:

Hi Jim – I posted this response to the forum as well.



First, let’s discuss how hybrid vigor works. Crossing two species or subspecies increases heterozygosity, or the likelihood of having dissimilar genes for any given trait. This may make the animal more fit in a changing environment because it may have genes for several environmental conditions (e.g., hot or cold tolerant). However, when F1 hybrids interbreed in successive generations, they become more and more homozygous, and the genes retained may not necessarily be the “best” for any given trait (e.g., slow growth, low aggression, etc.).



There is a fair amount of literature addressing introgression and outbreeding, which has been demonstrated with many species. There is no reason to believe F1 bass would be any different, so if the potential for regression is there, we (Extension) must approach these stockings with caution. It doesn’t mean that someone who wants to intensively manage their pond can’t use these fish as a management tool. However, it would not be a good idea for not-so-intensive managers to stock ponds with F1 hybrids and expect to have excellent growth 20 years later.



I list a few studies that you can check out below. You’ll notice similar names on all of the papers because they are the primary researchers working with bass genetics. One study that addressed the potential for outbreeding depression is:



Philipp, D. P., J. E. Claussen, T. W. Kassler, and J. M. Epifanio. 2002. Mixing stocks of largemouth bass reduces fitness through outbreeding depression. Pages 349-363 in D. P. Philipp and M. S. Ridgeway, editors. Black bass: ecology, conservation, and management. American Fisheries Society, Symposium 31, Bethesda, Maryland.



This study did not directly test the outbreeding depression of F1 hybrids – instead it looked at the effect of stocking one genetic stock on the other. However, the mechanism is the same.



Dave Philipp had several earlier papers that addressed the potential for later generation intergrades to have reduced performance:



Philipp, D. P. 1991. Genetic implications of introducing Florida largemouth bass. Canadian Journal of Fisheries and Aquatic Sciences 48 (Supplement 1):58-65.



Philipp, D. P. 1992. Stocking Florida largemouth bass outside its native range. Transactions of the American Fisheries Society 121:688-691.



Philipp, D. P., and G. S. Whitt. 1991. Survival and growth of northern, Florida, and reciprocal F1 hybrid largemouth bass in Central Illinois. Transactions of the American Fisheries Society 120:58-64.



Another paper that I recommend is:



Kassler, T. W., J. B. Koppelman, T. J. Near, et al. 2002. Molecular and morphological analyses of the black basses: implications for taxonomy and conservation. Pages 291-322 in D. P. Philipp and M. S. Ridgeway, editors. Black bass: ecology, conservation, and management. American Fisheries Society, Symposium 31, Bethesda, Maryland.



In this manuscript, the authors offer substantial evidence that suggests “Florida bass” and “largemouth bass” are two separate species.



As for mixing coppernose and regular bluegill, the same mechanism are present to lead to outbreeding depression, but I have not see anyone address this. However, with both hybrids, it is reasonable to suggest that the effects of outbreeding depression in the Deep South would be less noticeable than in the north. For instance, Florida alleles may be more of a hindrance in Ohio than southern Mississippi. But this has not be testing directly.









From: Jim Burkes [mailto:j.burkes@sbcglobal.net]
Sent: Monday, December 08, 2008 9:45 PM
To: Wes Neal
Subject: F1 outbreeding problems



Mr. Neal, I just read about this phenomena on the farm pond forum and posted this response:

I have read consideraby about northern vs. fla. vs F1 and this is the 1st time have seen any mention of this regression of quality bass traits. I would think since they are effectively the same species, this would not occur. I can see that this outbreeding regression would occur, as in HBG, but does this also occur in a mixed population of CNBG and standard BG? Has there been any studies with empirical evidence of this taking place? I will have to post this on the "Pond Boss" forum and get feedback from the many fisheries experts who frequent that forum.

Again,I would like to have the oportunity to read any available studies, since I just stocked F1s in my pond, even though their primary function will be control of BG for trophy BG fishing. I also stocked a 50/50 mixture of CNBG and BG as suggested by most authorities, my pond being in south Ms.



Do you have more information?



thanks for your time,

Jim Burkes

Guess I'm stuck with my mutt bass and perch. I may have to do some managing. Cecil get the backdrop and props ready for the 2# 'mutt' bluegill.

Last edited by burgermeister; 12/09/08 10:16 PM.