While on a recent vacation in the Dominican Republic, I was thrown for a loop with a fish I hadn't eaten before. One of the most popular local species is parrot fish. I visited a waterfront restaurant, and the staff all spoke Spanish. We had some trouble communicating about whether the fish was a filet or whole and how large it was, so the server brought several out for me to see. I was not impressed. They were whole fish, but the skin was sloughing off, the eyes were sunken-nothing I would ever want to show a customer. But they smelled clean. This was the only reason I didn't change my mind and order something else, even though I questioned my decision.
When the dish came out, it was beautiful and smelled wonderful: a whole fried fish, black beans and rice, plantains, some sautéed peppers. It was delicious and tasted fresh. So, even though the fish failed my visual checklist, it passed the smell test, and it turned out to be great.
So when it comes to fish, or any food, trust your nose. If you ask to smell one of the filets at your local grocery store, and they refuse or try to tell you not to worry, change your dinner plans. Is this fish fresh? Sniff it. Has this been in my refrigerator too long? Put your nose in it. It won't let you down.