Mackerel have scales. The scales are just very small and smooth. I would rather eat some ocean caught mackerel than a farm raised fish. The reason or part of the reason why the bible says not to eat certain sealife is because certain molluscs and crustaceans are filter feeders and trash feeders. Part of their job is to clean the oceans. Unfortunately, due to our pollution of the atmosphere, there is a certain amount of mercury in the oceans and apparently ocean roaming fish are not immune to being contaminated. I bet the gulf stream and other various tides of the world help distribute it. This is why I take open cell chorella. It helps eliminate mercury from my system.