I can see I'm gonna' be late for work this morning..
HBG have got to be one of the most misused, misrepresented, and misunderstood, (at least by the general public), fish out there. I have one of my ponds dedicated to this fish, and I will share what little I know.
First, the term "large" means different things to different people, and can be relevant to one's location. What is your idea of a large panfish? You might be hard pressed to find a HBG over 2 lbs, while a pure strain BG can exceed that, and a RES obviously can too. A RES x BG hybrid? I don't know what one is capable of topping out at.
I have had mine for almost three years now, and most of my catches weigh over a pound, with a pound and a quarter being my largest thus far. My goal was to get them to a pound and a half, which should be relatively easy to attain. Mine are stocked with LMB, and a few RES.
The advantages of a HBG, as I perceive them:
Predominantly male, greatly reduced chance of overpopulation and stunting.
A large mouth allows them to forage on a greater size of natural prey, INCLUDING, their own offspring... I have witnessed this many times. This reduces competition for the available food sources, while providing an immediate boost to the fish that consumed the offspring... a one two punch.
They grow very quick for the first couple of years, faster than RES or BG. Their growth slows after that time, allowing BG to overtake them, growth wise.
They are tremendous fighters, stronger than a comparably sized BG.
As you stated, they are readily available.
When it comes to RES x BG hybrids, my knowledge is limited to those I catch in my other ponds. And I have caught some large ones, although none that weighed more than my largest hybrids. To be fair, I have only started supplemental feeding those fish last year, so time will tell what can be achieved.
You've probably already seen this but here is more info:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=256325#Post256325I'm curious, what are your expectations of a RES x BG hybrid?
