Someone I know real well spends a lot of time fly fishing rivers in eastern Idaho and western Wyoming. You might think that bears would be his main concern - but actually, it's moose that make him nervous. They sneak up on him all the time. It's the moose that convinced him to carry a big bore revolver. Convinced me too. Make mine a stainless DA Ruger. Easy to deep clean after a swim. Any number of rust resistant heavy loaded 45acp or 10mm would also suffice.
