I agree with the saltwater soak overnight whenever possible. If you are still getting a little off-flavor try soaking in milk - especially buttermilk - overnight. See if that suits you.
Here's a little worthless tip. Take the bones of fillets and chop off the heads. Steam the bones. The leftover flesh - even though its not much it does add up - can be used for seveal things. I add mine to Ramen noodles + hoisin sauce or a orange sauce. Nice lunch at work. Flesh can also be used to make fish cakes. Not bad.
By the way, nice catch. Good size. Hope to get out for some myself as soon as things get tight again.