Let me answer Dave first - Outbreeding depression can occur in several ways, but the one I am most concerned about is through the breakdown of biochemical or physiological compatibilities between genes in the different populations. For example, Florida bass have genes (genetic material) selected for positive, overall effects that are produced when combined with other Florida bass genes. Due to nonadditive gene action, the same genes may have rather different average effects when combined with northern bass genes. In other words, Florida bass will tend to have genes selected for the quality of combining well with gene combinations common in in othe Florida bass. However, Florida bass genes will not have been selected for the quality of crossing well with genes common in northern populations.
Yes, the world record bass was probably an intergrade between the two; but that intergrade had many thousands of years to select for the right genes for its habitat. That is very different than artificially mixing genetic material in the short term.
As for Chadwick71's question, think about it this way. Say you come into a 20 year old pond that was originally stocked with F1s. It is all Fx at that time, and you supplementally stock 10% more bass that are pure Florida. Only 1% of the next generation will be pure Florida, and 99% will be Fx fish, because they are breeding with Fx fish. So you have a limited effect with supplemental stocking. Stocking F1s will give 100% Fx the next generation.
Generation Fl No F1 Fx
20 years 10.00 0.00 0.00 90.00
Gen 1 (%) 1.00 0.00 0.00 99.00
Gen 2(%) 0.01 0.00 0.00 99.99
But for you fish producers, imagine what could be accomplished with a sterile (triploid) F1 hybrid! You could take two approaches. Approach 1 would be to stock only triploid F1s every year and have a completely controlled population with hybrid vigor! Approach 2 would be to establish a Florida bass population and then supplement with triploid F1s - this would maintain genetic integrity while also providing F1s to catch.
