The UK's Food Standards Agency (FSA) has issued a warning about the consumption of shark, swordfish or marlin after a survey discovered relatively high levels of mercury in the fish.
"Pregnant women, women who intend to become pregnant, infants and children under 16 years of age should avoid eating shark, swordfish and marlin," the agency said in a statement.
Mercury, found in fish in the form of methylmercury, can harm the nervous system of an unborn child, while infants and children may also be at greater risk of mercury poisoning because they eat more food relative to their body size than adults, the statement advised.
The Agency stressed that occasionally eating shark, swordfish and marlin as part of a balanced diet was unlikely to cause harm to other adults, although it added that consumers should not eat more than one portion of these fish per week, as a precaution.
The FSA said it had analysed 336 fresh, frozen and processed sea fish and shellfish for mercury, but levels in fish other than shark, swordfish and marlin did not give cause for concern.
The independent expert Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment will consider the results of the survey at its June meeting and issue any further advice if it feels it is needed, the FSA said.