The obvious answer is to use a larger hook...But that does not always work.

Most likely the smaller fish are schooling in the area. You will probably find there is an under water barrier line, like a sand bar or rocks etc. If you move at say 5 or 10 meters at a time, you will find the edge of the school of small fish. The larger fish will likely be out side the school of smaller fish.

If there are larger fish amongst the smaller ones. Then you could try a burley. Throw the burley to one side and your bait to the other. The smaller fish will chase the burley leaving your bait for the larger fish.

There is a saying that if all you have is a hammer, then everything looks like a nail. Because my fishing is almost always livebaiting, I would take that little pest, put a livebait or circlehook on it and 'send it'. A bigger fish is the only thing that'll eat it. The problem of little fish will go away. But this suggestion is only because I see livebaiting opportunities everywhere I go, like a hammer looking for a nail.

And, yes, bigger snapper will eat smaller snapper.