You can't drag dead fish on a stringer behind the boat for several hours and then expect them to have an excellent flavor later in the day.
Fish are like any other kind of food.
Whether you plan to freeze , can , smoke , pickle , or eat your catch fresh , care must be given to preserve the flavor and keep them from spoiling. In general, small fish are more perishable than larger ones, and deterioration in dressed fish is slower than in whole fish, but the latter are spoiled more readily by bacteria. Also, these changes occur more rapidly at summer temperatures and more slowly at cool temperatures. Proper preservation begins the moment the fish is hooked and pulled from the water. How you initially handle a fish can greatly affect its quality, taste, and storage life.