While I've never had the exact same experience, I do somewhat understand what he's talking about.
Sometimes I detect this particular metallic smell out of nowhere; this seems to happen randomly, but I believe that it mostly happens when I either get strong headaches/migraines or I physically strain my body in some way. Other times I get a weird taste/smell that reminds me of old oil or something.
While I don't eat a lot of seafood, I can imagine some of it having those tastes or smells to it