When it comes to choosing the right gaff for lingcod fishing, it ultimately depends on personal preference and fishing conditions. Both the methods you mentioned have their advantages and it's important to consider the size and behavior of the fish, as well as the ease of gaffing and landing it.
Downward force gaff (Top of the skull): This method, commonly used in BC, involves applying downward force onto the top of the fish's head. This technique aims to immobilize the fish by controlling its head movement. It can be effective for lingcod, as they have a bony skull.
Upward force gaff (Underside of the head or side): The technique you observed in videos from Alaska, California, Florida, and the Caribbean involves using a longer gaff and pulling upward into the softer underside of the fish's head or its side. This method offers more leverage and can be effective with lingcod as well.
It's worth noting that when using a downward force gaff, accuracy and proper technique are important to ensure a successful gaff. Deflection can occur if the angle or force applied is not optimal, resulting in a missed gaff.
Ultimately, try experimenting with both methods and use the one you feel most comfortable and confident with. You may find that one technique works better for you in specific fishing situations or fishing grounds. It's also a good idea to talk to experienced anglers in your local area or fishing communities to gather more insights and recommendations based on their experiences with lingcod fishing, just as you have here in this forum.