While the Lions played one of their best games this season, the Sharks played their worst home game for years.
After getting their season back on track last week, the Sharks failed to show up and now need to dig deep to be a force in the premiership race.
The win could set up a big second half of the season for the Lions who are still to put their best team on the field. South Perth led by 28-6 at halftime and were more committed and enthusiastic in defence, looking like they wanted to win.
The Sharks now have to go back to the drawing board and need to win the next two games at Lark Hill against Joondalup and Kalamunda to stay in the premiership race.
Best players were Duntaine Puna, Vincent Silulu and Blake Nicholls in his first game back from a broken jaw.
In other results, the Sharks’ Premier Grade team defeated South Perth 48-6, the Ladies League tag team beat top side Souths 14-12 on the bell, the U18s went down 44-24 and the Reserves won 48-6.