Unless you have an amazing fishmonger, or caught the fish yourself, the week-old cod you're buying from the supermarket will most likely reek. ... The fish should smell fresh and mild, not fishy, sour, or ammonia-like. The eyes should be clear and bulge a little.

What does bad cod smell like?

Three rules of thumb for fresh salmon and cod

Shiny and dry surface - when it starts going bad, it gets a slimy greyish coating. Fresh odour - it can also smell like melon or cucumber. If it's bad, it will smell rotten, like a sour dishcloth.

Is it OK to eat fish that smells fishy?

“Fishy” odors begin to develop in fish immediately after they are caught and killed, as bacteria on the surface break down the compound trimethylamine oxide into stinky trimethylamine. As long as the flesh is still firm and the skin is shiny rather than slimy, this fish is still fine to cook and eat.