Geo is right, it's really hard to get good seafood this far from the ocean (I think that's why so many people around here say they don't like seafood). And if that really is raw striper, I'd want it it to be from the ocean, not freshwater. But contrary to popular belief, sushi does not mean raw fish, and a lot of it is actually cooked, although usually very briefly. The word "sushi" in Japanese refers to the rice - it literally means "sticky rice." So what they're serving might be cooked striper; I would ask.

But the other point about the mis-identified fish is an excellent one. After all the reports I've seen about how most of what is served is sushi restaurants isn't what they say it is, I don't think I would trust any of them.

That said, the only times I've caught stripers have been out of saltwater, fishing with my brother, and both times we cut off the cheeks and ate those raw, when we were cleaning the fish. And they were delicious!