Hi Andy this is more common with cockers than most spaniels , the answer lies in the fact he would rather hunt than retrieve . You should stop all hunting and work on the retrieving , my approach is to teach what we call the hold .Start in your garden or house sit the dog and offer it a dummy if it doesn't take it then you open his mouth and put the dummy in ,then with one hand on top and one underneath his mouth gentle squeeze and repeat the verbal command HOLD .If when you take your hands away he drops it then repeat until you can remove your hands and the dog holds the dummy .Next stage on