What happens to biological productivity in areas where two major currents meet?

Areas where cold and warm currents meet have a tendency to have regular foggy situations, as the overlying warm and cold air come in contact with each other. They also have a tendency to have high biological productivity, because plankton growth is embolden by the mixing of warm and cold currents. Some of the world's most productive fishing grounds are situated where warm and cold currents meet. For example, where Labrador Current (cold) and Gulf Stream (warm) meet, a dense fog is there and it is one of the richest fishing grounds of the world.