I too would have to agree with Mark and Kujo. This is a very unusual year for tuna, generally the tuna fishing is just NOW starting up in most years.
This blow that we're having now should really improve things. Keep watch on the site for when people are posting SST's and you'll see much better and sharper temp breaks appearing.
In a 'normal' year the tuna fishing usually lasts clear into late September. As early as they showed themselves this year, who knows? October? December?