If the Fulton Fish Market is closed on Sunday, then it would follow that most restaurants serving fish on Sunday are serving fish that is at least a day old. Restaurants that have fish delivered from alternative sources would not be included, of course, but do those sources deliver on Sunday? Probably not.
Am I incorrect to be suspicious that fish served on Sunday may not be as fresh as during the week? Am I wrong to cringe when walking past a sushi restaurant and seeing patrons eating raw fish that is not the freshest it could, or should, be?