Most states don't allow you to discard dead fish within a certain distance of a waterway.
Like NY its within 150' of a waterway.
Whether its a shot fish, dead bait, fish that died while handling, etc...
In ny cannot be thrown back in the water.
There are grey areas, that I would leave up to the individual.
Such as what to do with an undersize fish. Or out of season fish that dies in your possession?