[FlyingStart]

No.. If he's a good player it could mean that, but in general if he is tight, he is less likely to bluff. Game theory so to speak

edit: I mean, if one were to use the agrument that he was loose and somewhat aggressive and therefore might be bluffing, it is not possible to use the argument that he is tight and therefore also is bluffing. In that case he would always be more likely to bluff..