Back to the GSF. When the GSF and BG come together, like in many of the ponds represented in this thread. Jim in your experience and observiation, do the GSF or BG traits dominate? I'm guessing you see hybrid vigor through the first gen. I have read that the GSF traits dominate and over time the HBG look more like GSF than a BG. Can the cross go both ways...male GSF X female BG or male BG x female GSF? If not why? Also I have read that the majority of HBG are male...what causes this? They are not sterile like a mule or do you see that??
Sorry if I'm asking to many questions but when they pop in my head they don't leave until I ask...yeah I was that kid in school. lol
To my eye the F1 hybrid is intermediate. Never played with direction much on that one but to my understanding it will go either way naturally if female of a either species is having a hard time finding a conspecific mate. The hybrid does feed more aggressively but in my food-fish setting the pure Bluegill outperforms the hybrid and pure Green.
Hybrid Green x Bluegill do have reduced reproductive output but possibly for more reasons than simply fertility. Reduced fertility is low when hybrid bred to hybrid due to aneuploidy (look it up) but not as bad when backcrossed to either parental species of even a third to make a trihybrid. Mismatch of behaviors is what I see to be a real problem for the male hybrid where they put nest close together like Bluegill but defend larger area like a Green. This can be a real problem when defending nest bound brood. I suggested that to Roy Heidinger when I was a student but I do not think he gave it much credit. The more I have watched the more confident that mechanism also operates. Behavior of hybrid fry and fingerlings may not be good for avoiding predators like LMB. If you get the chance, try to observe how a Bluegill vs Green Sunfish behave when threatened by a LMB. They differ.
Sex determination mechanism not well worked out. Look for a paper by Wang on the subject. I will assert based on over a hundred broods where we tracked sex ratio that it is genetically based on not like mammals or birds and it involves either multiple loci or alleles. Matings between individual Bluegill can give skewed sex ratios that rival that of hybrids. Skewed can be strong or weak and towards either male or female. Somehow males promoted by heterozygosity and hybrids really push that.
Green x Bluegill are not sterile as indicated above. There are some hybrids that are dead sterile (no fertility) or only one sex is fertile. More funky stuff we have seen where viability is strongly impacted by direction of cross.
More could be said about sex ratios but that would require a sit down.
