You don’t examine the fish closely before buying
Start with the eyes. A whole fish should have a clear, bright eye (not a clouded, murky one). “The fish’s eye is the window into its age and the way it was treated,” says Hartnell. A whole fish should look shiny, and there should be no sliminess covering its surface (a sign of decay). Fresh fish flesh is firm and bounces back when you press into it. And, as counterintuitive as it may be, fresh fish should not smell “fishy.” It should smell like the ocean. A “fishy” smell means that fats inside the fish have begun to oxidize, a sign of decay and age.