I never thought I'd find a place on Chow for this, but then this came along.
Several times a year, fishermen drop off fresh caught trout at chez moi. The flesh is excellent, but I can't stand to waste the left over fish skins, bones, etc.
Mr Shallots objects to dead fish residing the frig, so I've taken to roasting the fish, just to dry out the carcasses. I usually take a hammer to them and spread the remains (reverently) around plants that appreciate such things.
Then, instead of just washing the roasting pan, I treat it as if I were making a gravy, but I save the liquid. What I'm seeing is that the dilution of the liquid makes an excellent and surprisingly unfragrant liquid fertilizer for my indoor begonias and citrus trees.