Obedience training, stay alert
, and use that prong collar to keep his attention.
I have a high prey drive male myself, although he is only 85 pounds, he can still pull me off my feet if I don't pay attention. I make sure that if I have to glance behind me or otherwise take my attention off of him, even while on a casual walk, he is sitting, and I have hold of his collar (he wears a buckle collar with his tags and the prong when we're out walking) just in case something tempting crosses his path.