Fishing with treble hooks can range from trout fishing to giant tuna. These wide range of hooks are very effective in keeping the fish connected since multiple hooks points can hook the fish. The higher the number the smaller the hook unless it has a "0" behind the number. For instance, Size 18 would be very small and used for trout or panfish. Size 18/0 would be used for tuna or giant trevali and are very large. The larger the hook the larger the diameter of the wire used.