Fishes can be quite slippery. Slimy even. Grabbing hold of one can be rather challenging. There are exceptions of course, sharks for instance are famously unslippery (though one might be wary of grabbing a shark for reasons of personal safety). At any rate, fish-eating fishes have had to deal with the problem of slippery prey for ages, and have come up with two main solutions. The first is suction-feeding, where the predator creates negative pressure in its oral cavity to suck in and swallow its prey, thus avoiding the need to grab onto the slippery victim. The other is to use teeth. Lots and lots of teeth.
When it comes to teeth, predatory fishes can have quite a mouthful. There’s teeth in the jaws, of course, but quite often also on the palate and the gill arches. Moreover, these teeth are usually very sharp and curved backwards. All in all that makes for a very effective grabbing-and-holding-on-to-stuff device for dealing with slimy prey. However, it also has a slight drawback. For what if you catch a fish that is a little too big for you to swallow? The sensible thing to do would be to spit it out again of course, but if your mouth is effectively a one-way street, this becomes rather hard. It will come as no surprise therefore that there’s a number of fossils showing a fish that choked to death trying to swallow another one.
It’s not that this happens to fishes daily, of course, and these fossils are rare. But with some luck one can occasionally catch them in the act. So kids, remember to chew your fish before trying to swallow it.