If you go to the fish market and your question is "Is this fresh" So they're going to say, "Yes, this is fresh." So that's not the right question because they're supposed to sell fresh fish in the fish market.
So you have to ask them, "Is this fresh enough to eat raw? I'm going to make sushi. I'm going to make sashimi. Is this sushi quality fish?" And if they say, "Yes." You should still not believe them. They say, "Yes. Yes. Yes," to clients, to customers all of the time so you have to talk to them. Tell them, "I'm going to invite my friends. I'm going to have a party and I don't want anyone to get sick and I have to come back here to report to you that all my guests got sick." And those kind of things.
Then they'll start kind of talking to you a little more honestly. Like if they don't know anything about the sushi they'll say, "Well, I don't know anything about the sushi but I just got it this morning and so it's supposed to be fresh." Then don't buy it. Don't buy it. That guy, or the person doesn't know anything about the sushi or sushi quality.
Another thing, if you go to the fish market and they try to sell you something you've never seen in a sushi restaurant, for example, blue fish. Have you ever seen blue fish served in a sushi restaurant? No. But some fish markets will say, "Well, I just got this this morning. This is fresh. You can eat it raw because I just got it this morning." Don't believe it because he doesn't know anything about sushi. There's a reason for why you don't serve blue fish as sushi, so don't believe it.
Some fish are more eco-friendly fish. For example, squid, sweet shrimp which is called amaebi, abalone, and sea urchins are eco-friendly. Tuna, like yellow fin tuna is okay but not the big blue fin tuna, it's not eco-friendly but it doesn't mean those fish are tasty to you or not. So you have to think about it. I like blue fin tuna. If I eat tuna I only want to eat blue fin, but I don't eat tons of it, I just eat a little bit once in a while so that you can't pace out to save the earth.
Those are things you can think about when you're purchasing the fish.