fish n chips, the 1/3 rule is most often applied to BG, when it comes to shad its even more. When it comes to a bass eating fish like trout and other LMB, they can eat even up to 60% of their length.
This is from a chart in the back of Bob Lusk's book Raising Trophy Bass
These are for LMB when I say "Bass"
Bass Length 12.5 can eat Gizzard Shad 5.37 BG 4.09 and Bass 6.65.
Bass length 22.5 can eat Gizzard Shad 12.02 BG 8.77 and another bass 13.98inch.
I would have to see a bass eat a 9inch bg or 12inch GS tho, that just seems outrageous. be we are talking about a 7lb bass doing this too.
So a bass 22.5 inch can eat another bass that weighs just over 1 lb.