He also won silver medals in the 100m backstroke and the 100m freestyle, bronze in the 100m individual medley, as well as in the 50m backstroke and the 50m freestyle.
Prime has picked up where he left off in 2014/15 season, where he won 12 national medals across the short and long course formats.
Another seven Northlanders won national medals, with the Northwave trio of Ciara Smith, Ellie Eastwood and Hayley McIntosh, as well as Bream Bay's Paul Linton, all securing multiple medals.
In the girls 14-years age group, Smith secured a gold medal in the 100m breaststroke, a silver medal in the 200m breaststroke and a bronze in the 50m breaststroke.
Eastwood won two silver medals, in the girls 15-years 100m and the 200m breaststroke, while McIntosh won a silver in the 400m freestyle and a bronze in the 200m backstroke in the girls 16-years age group.
McIntosh and Eastwood came close to further medals, with McIntosh placing 4th in the 200m and 800m freestyle, and Eastwood 4th in the 400m individual medley.
Eastwood also made the women's open final for the 400m individual medley, placing her among the top open swimmers across the country for this event.
Single national medals were won by the Northwave trio of Annabell Simpson (girls 14-years 200m backstroke), Jeremy Elliott (boys 14-years 50m butterfly) and Mia Gordon (girls 13-years 50m breaststroke).
Top five placings went to the Bream Bay duo of Kieran Swords (4th in the boys 16-years 50m butterfly) and Isabelle Paton (4th in the girls 16-years 200m breaststroke), while Josh Young (Northwave) and Conor Swords (Bream Bay) recorded top ten finishes.
Eastwood, Simpson, Smith and Linton have been selected to attend the 2015 NZ Age Group Development Camp in October, where they will join Prime, McIntosh, Paton and Elliott, who were all selected following the NZ Age Group Long Course Championships earlier this year.
