Rule of thumb:
The bigger the fish regardless the species, the larger the lure it will go after.
The following is for those that use jigs and soft plastics.
This 15" crappie attacked this 4" swimbait as did others in the school:
...along with this 4" Kut Tail worm:
If a shorter lure has the right shape and action,
all size fish will attack it like this 2" Crappie Magnet:
...and 2.5" curl tail:
As important as lure size is
hook size and
jig weight when using soft plastics on jigs. Too short a hook misses hook sets; Too long a hook limits lure action.