Be Careful with Gaffs
Gaffs are made to stick into the fish and hold it so you can land it. Gaffs are big hooks on the end of a handle and allow you to reach down and grab the fish. Some are made to stick into the mouth of the fish and others are made to hook into its body. On some gaffs the hook remains on the handle as you bring the fish in; on flying gaffs, the hook attaches to a cord on the handle, and the cord comes off when the fish is gaffed, so you land the fish by pulling in the cord.
Good Things about Gaffs
A gaff is a good way to secure a big fish and get it into the boat. The handle of a gaff will support the weight of a large fish, and a flying gaff with the hook attached to a rope can be used to land very large fish. When fishing from a big boat with high sides, using a gaff allows you to reach down and get a solid hold on a fish and control it. Gaffs are also good for use from docks and piers if they're not too high above the water.
The point of a gaff must be kept sharp and a cutting edge is best. When trying to penetrate the side of a big fish like a king mackerel, the point must be sharp enough to go through the scales and any bones it hits to go deep enough to securely hold the fish.
Bad Things about Gaffs
Gaffs stick into the fish and injure it. Even if you lip-gaff a fish, there's damage done to it and it's less likely to survive. Gaffs are sometimes hard to stick into the fish and must be kept extremely sharp, especially the ones made to hook into the body of the fish. And gaffs can break or pull loose, causing you to lose a fish that is mortally injured.
Gaffs are usually used in saltwater and the blood released in the gaffing process can attract sharks. The sharks may get your next fish before you have time to land it. Having a shark eat the fish you're trying to land is not something you want to happen, but it's a fact of life for saltwater anglers.