There's a cardinal sin that professional chefs urge patrons not to commit when ordering seafood, and it's an easy one to avoid: Don't order seafood at a non-seafood restaurant.
(or shouldn't) order the filet mignon at a diner, avoid ordering the lobster, oysters, or Chilean sea bass from a place that doesn't specialize in seafood.
Steve Chiappetti, executive chef of the Albert restaurant in Chicago, advises against ordering fish "from restaurants not located on the coast or that are not known for seafood."
Specialized seafood restaurants source fresh seafood frequently. Other restaurants may only include it on the menu for variety and to provide options for dietary restrictions.
However, "That stuff will often be made with older ingredients and by people who aren't used to making it since it comes up so rarely in a night," a Reddit chef adds.