Herding would be a great idea, because he will be taught to obey your signals/commands...which include STOP! and WATCH! He will learn it's OK to "herd" when called upon, but it's NOT OK to simply chase anything that runs.
Long line boot camp is a great idea, as well. I would consider doing both. The long line will give you the needed "let's nip this behavior in the bud" for now. The herding classes will give him an appropriate outlet. He can actualize, APPROPRIATELY, what was bred into them many years ago. They were intellegent, strong, versatile, and had many uses...one as a drover dog.
My friend has had each of her dogs in herding classes. She thinks it's the best thing since sliced bread. Haven't done it myself, yet. I've watched!
