The cannery I worked in would pack the sockeye with 'head' oil. They'd take all the fish heads, grind them up into a paste, then pressure cook it to separate the oil. You'd end up with a pretty stinky red oil and they would put a justs few drips into each can.

They only did this with sockeye, not pinks or chums. I suppose this has to do with the oil content in the sockeye, but it might be interesting to try with springers, or coho, or kings in general. You just need to figure out how to grind 'em up.

Who knows? This might be a good way to milk out some extra Omega-3's too (if you're into that kind of thing).