I am strictly going off memory here (from PB posts) but I've read about 1 to 3 ratio, regarding LMB length and the necessary gape size for larger prey fish. So the thinking is, a 12" LMB could handle up to a 4" BG. Add to that the thinking that, the LMB would expend less energy on chasing and eating ONE or TWO 4" BG than 4 or 5 two to three inchers.
So so how does the 100 to 1 mass size ratio correlate to the above?
No the mass ratio is about 15 to 1. A 4" BG provides roughly 6.67% of a 12" LMB's body weight. It is enough to sustain 12" LMB for four days and if 12" LMB can eat one every day for 30 days he'll gain >30% of his body weight
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Here is spreadsheet where you can play with the mass ratio: