Supermarket employee here. We have a “fresh” fish counter selling stuff like whole mackerels and raw salmon fillets and the like.

Each and every one of these has been frozen at least once - this is a mandatory health hazard prevention thing (to kill off parasites etc) and also basically the only food-safe way to transport them in great quantities over long distances without them going bad. They get delivered frozen solid, get thawed behind the scenes and then put on display / on ice for customers to buy. And then they’re lying there all day long until someone happens to buy some … people still treat the pre-packaged fish from the frozen foods aisle as a second choice, even tho those have NOT been lying around half-thawed in the open air for 10 hours straight.

Long story short, “fresh” fish from the counter is less fresh than the frozen stuff, despite customers commonly believing it to be the other way around.