One way that food laced with chemicals could be selective is by having it be at different heights in the water column. A heavier pellet that would sink rapidly would target more catfish and carp rather than BG or LMB. Even if you did floating pellets isn't it the desire of every pond meister to reduce number of bluegill, GSF, and 14" or smaller LMB? Certainly this wouldn't be a great option for ponds with pellet trained HSB Not sure WE or SMB would be at risk depending on how pellet trained they are.
A larger pellet size would be a more selective way to target different fish. Large 'hand toss' pellets may not be as readily consumed by panfish Different fish have a different 'lethal dose'. Papers show befenthrin as a neurotoxin is more selective for carp than for gamefish in lower concentrations. Could consider a breadball laced with chemical or a different medium (fish fillet scraps soaked in toxin?) compared to a pellet.
It seems these studies are pursued in relatively small ponds, canals, impoundments where the goal of eradicating catfish or carp temporarily is a larger priority than any simultaneous loss of gamefish or panfish.
