Gang Hooks are a series of fish hooks linked together on a line. They help to keep the larger bait such as pilchard/mulie in better condition by holding it together and making it appear more natural. Gang hooks also ensure that the bait has a better coverage on hooks which means that wherever the fish bites the bait there is more chance of it being hooked. They lessen the change of the fishes teeth coming into contact with the line thus reducing bite offs. So whether you are a beginner or a pro fisherman and want to get the best chance of catching those fish, make sure you have a supply of gang hooks in your tackle box.
Source: Terminal Tackle & Rigs