"Fresh" and "fish" just go together. The fresher the fish when you cook it, the better it is to eat.
Take a fish off the hook, fillet it, build a fire on the shore and cook it. That's fresh. But this quick treatment is not usually practical either.
Here is a suggestion passed along from experienced fish cooks at the Arkansas Game and Fish Commission. They did not originate the secret but picked it up from some renowned chefs who handle fish and handle it well.
This is for wild-caught fish. In Arkansas, that can be catfish, largemouth bass, crappie, bream, catfish, walleye, trout - you name it.
Mix two tablespoons of table salt, one teaspoon of baking soda and a gallon of cold tap water. Stir well so the salt and soda are thoroughly dissolved. Put your fish fillets in a container, cover with the salt-soda solution and refrigerate overnight.
Remove the fish from the solution and rinse well with cold water. Pat with paper towels to dry. Proceed with your normal fish cooking method - fry, broil, bake, grill, smoke.
What the soak in the solution does is to greatly reduce the "fishy" taste some eaters object to and to remove any foreign taste, like muddiness, from the fish. The result is sweeter tasting fish, and this likely will produce favorable comments from people around your dinner table.
If time for soaking in the solution is a problem, less than overnight will work nearly as well. Four hours in the solution should be a goal, however.
Cover the container while the fish is soaking in the refrigerator. One idea is to use some empty and rinsed cardboard milk or other drink containers. Plastic containers with lids work well also. Discard the used solution after soaking. Don't try to save it for another batch of fish.