Sunil's "rule of thumb" is usually pretty good guidance.
However, I think trout may break the rule. Trout are almost perfectly gullet shaped (fusiform). They also do not have any spiky rayed fins.
Personally, I would not be shocked at all to see a 12" LMB attempt to eat an 8" trout. If you have a few bass over 12", then I think they might even try for a 10" trout if they were feeling particularly feisty on that day?
I am pretty sure the momma bass did not give their babies a lecture about not biting off more than you can swallow!
(I am definitely NOT an expert on this topic. Just have watched bass on many occasions try to eat things that were ridiculously large for the optimistic bass.)
