With strongly flavoured meaty fish such as tuna, New World wines are a great option. Have a go with fuller bodied white wines such as Semillon or Aussie Chardonnays.
Sauvignon Blanc appears again here as a match but also look at Sauvignon Blanc blends. You could consider Pinot Noir Cabernet Francs as well as lighter Beaujolais styles. Some of the new wave Argentinian Malbecs would make for a good alternative.