In a lot of areas, the fish head is considered a delicacy ....I used to work with a gal who always pleaded with me to save her the heads, which I did. I always had to cut a bit extra far behind the head so she had what I considered to be real fish, but I'm sure she would have been just as grateful for what she asked.
To me fish heads and carcasses belong in the crab pot.....and salmon bellies belong on the fillets. Ain't differences great?