Unfortunately Clamperl doesn't evolve through leveling-up for some unknown reason. However, it does evolve, and that happens through means of holding certain items when traded. Clamperl>Huntail when Clamperl is Holding Deepseatooth when traded Clamperl>Gorebyss (ugly sod) when Clamperl is holding Deepseascale when traded. I recommend Huntail, if you're thinking of choosing. I recommemd choosing, if you haven't thought of choosing.