If you plan to keep most of the fish you catch, it is important to be prepared to do so in a manner that preserves their eating qualities.
The two best choices to preserve their eating qualities are to keep them alive, or ice them immediately. Fish flesh deteriorates rapidly after the fish dies. Allowing fish to die while you continue to fish will adversely affect its edibility.
Keeping fish alive is relatively easy if you use a stringer or a fish basket. Stringers are a short piece of small diameter rope, or a chain with clips, used to keep fish while you continue to fish. The rope or clips should be inserted through a hole created for this purpose on the inside of its mouth between the tongue and cheek. DO NOT INSET THE STRINGER THROUGH THE GILLS. Inserting a stringer through the gills will likely kill the fish.
A fish basket is an alternative way to keep fish alive. It is essentially a basket made of finely woven wire with an easily accessed lid. The basket is kept in the water and fish are stored alive in it.
In a boat, a live well is a substitute for a fish basket. A live well is a waterproof box on a boat that has a circulating pump to pump water into and out of the box in order to keep the fish alive. A cooler can be converted into a live well by adding a battery operated circulating pump.
Another option is to bring a cooler and immediately place the fish on ice. This will slow their metabolism down and keep them very fresh.
Smaller ice cubes will work better than blocks of ice. Also, the fish should be buried into the ice and not just tossed on top of the ice.
Most anglers looking for very high quality food will dispatch the fish prior to placing it on ice. A quick blow to the top of the head with a heavy wooden club is the best way to dispatch fish. An alternative method is to pith them by carefully inserting a knife blade into their brain. A short, thick, pointed blade works best.