He welded the two fish cut-outs together, then welded a pipe into the mouth opening and heated it up in the propane forge. The propane forge blasts like crazy - much hotter faster than the coal forge. Once iron is molten is moves like butta so he's actually blowing hot air (with the forge), into the welded iron cut-outs which makes it puff out.
So - the picture was for fun to send to his friends but the real story is below. I love being married to a blacksmith.