See if this helps you out. Cant take any credit for this.
You can't disguise the hook too heavily in the bait because you have to get it out and get it stuck in the shark. You also have to keep the bait alive. Try Mustad Seamasters - a round-bend offset hook - normally 10/0s, sometimes 12/0s, depending on the size of the fish that are available.
Take the hook through across the top of the back just ahead of the tail all the way through onto the leader. Then measure the hook midway down the fish and thread it up just under the skin so the hook lies horizontally down the flank with the bend away from the fish.
You've got to push through the same side of the mackerel each time. Come in from the starboard (right) side and lay your hook on the port (left) side so that the point is coming away from the fish. Otherwise, when you strike, your hook is going to dig back into the mackerel.
The less meat you've got on top of the hook, the quicker it's going to come out and penetrate the target and the longer the bait will remain lively. The hook should be placed in the middle of the bait for the best chance of a hook-up.