Possible Clues:

• Pieces of haddock served up, not this!
• Icelandic fish
• Fish heads from Cornwall or Devon
• No credit given to you that it's so fishy
• Source of some liver-based oil
• Picked up dwarf fish
• Rockling, e.g.
• '___: A Biography of the Fish That Changed the World'
• A white fish
• Cape ___, Mass.