Shock headlines in the media have reminded fish eaters that eating too much of one type can present potential health problems.
So what should people do when it comes to buying fish?
Mercury pollution is the problem and theoretically, over-indulging on one type of fish could bring about serious poisoning.
Mercury is a heavy metal, very toxic and is digested by fish and seafood that is consumed by humans.
The Fish Safety Agence (AESAN) has issued a number of warnings, particularly relevant to children and pregnant women.
The advice from AESAN centres on the types of fish available from the shops.
The belief is that large and predatory fish, such as swordfish and bluefin tuna, accumulate more mercury than smaller ones.
The concerns have led RASFF, the European Food Safety Alert System, to notify the Spanish authorities of the presence of mercury levels higher than the legal limit allowed in some slices of frozen swordfish.
This a modern-day paradox, as fish is recommended as part of a healthy and balanced diet. Eating fish is crucial, say the experts, as it helps maintain cardiovascular health. It is also essential for the embryonic development and good growth in children. It provides proteins of high biological value, vitamins A, D and B12, iodine and selenium.
So the rule of thumb is to alternate the type of fish people eat, with more sensitive groups avoiding the consumption of some types of fish altogether.