Anna - If you bury the fish deep enough (under the plant, so we're talking at least 6"), it shouldn't smell. And cats/dogs will dig up your yard if you put down almost any kind of fertilizer, I've found.. or maybe it's the type I use (I use all kinds, but I prefer fish types of fertilizers). That's another reason why I use so much mulch.
Big box pet stores (Petco / Petsmart) have to have a record of their dead fish because they get fish in such HUGE numbers. When they get their feeder gold fish, they get them in the 1000s. Literally thousands. Trust me, I know! I worked both! And when you stick 2500+ fish in a 90gal aquarium, you're gonna have a LOT of dead fish every day, just from the sheer amount of ammonia they produce. So they have to pull the dead, count them, then put them in the freezer because you don't want to just throw a bag of dead fish in the dumpster.. that'll attract all kinds of vermin (stray cats / birds / rats). So they store dead fish in the freezer for a week or so, then put them in a thick garbage bag the night before the dumpster's emptied & then it goes away the next day.
At least at the Petcos & Petsmarts here that's how it's done. And that's what the rules were...