I stayed right on Galveston Bay for a few months last autumn. Fresh redfish and catfish almost every night. Fried oysters, shrimp, and scallops. Was in a seafood lovers paradise.
But now I'm in Kentucky. The only fish I can get are the disgusting farmed raised catfish (raised on pellets and their own waste), or fish that were caught weeks ago and frozen into blocks. Needless to say, some pretty strong techniques are needed to cover up, rather than enhance the flavor. Frying has been a favorite method of mine, but strong marinates are gaining popularity with me.
There are two big problems with fish. The first is that the decomposition process produces ammonia. The second is that in smaller fish, their stressful deaths lead to the formation of lactic acid. I forget the exact mechanism by which this alters the flavor, but I think it hastens the decomposition process.