Higher mercury in Maltese waters means fish-lovers must choose well

Fish-lovers, get your diets sorted: elevated levels of mercury in Maltese waters should be a warning sign to calibrate your piscatorial intake.

It’s not really news that mercury is found in fish, but a recently published assessment by the Malta Environment and Planning Authority (MEPA) revealed that the amount of potentially harmful mercury in Malta’s coastal waters has exceeded the levels laid down in the EU’s Environmental Quality Standards Directive.  

The report, based on samples taken by different monitoring stations at nine coastal bodies during 2015, registered a “poor chemical status” for mercury in all areas.

But amateur fisherman and medical doctor Stanley Farrugia Randon says consumers should adopt a precautionary approach by eating certain fish in moderation, especially when it comes to children and pregnant women.

“We already recommend that fish like swordfish and Bluefin tuna are avoided when possible due to the fact that these fish are not environmentally sustainable,” Farrugia Randon, a member of Fish For Tomorrow conservationists says.

“The fact that they are top predators means that they have ingested a lot more pollutants from further down the food chain and are therefore more likely to contain high levels of methylmercury,” Farrugia Randon said, adding that the same can be said for shark species which Maltese people generally eat, like dogfish (mazzola) or “white fish”.

Farrugia Randon said that the fish that Fish For Tomorrow recommends as sustainable through their “Quickfish” guide are generally further down the food chain, like bogue (vopa) and mackerel (kavall). “This means that they contain a much lower concentration of pollutants like methylmercury and are also higher in Omega 3,” he said, adding that this means that eating sustainably also means eating healthier.

The presence of mercury in fish is worrying because of the health implications of having mercury build up in the body which, in turn, the body cannot eliminate,” Farrugia Randon said. 

 “A high concentration of mercury in the body can lead to mercury poisoning which can affect the nervous system and the brain among others,” Farrugia Randon said, adding that mercury is generally found in fish as methylmercury, which is highly toxic at high levels.

“Exposure to methylmercury can impair children’s neurological development and can adversely effect an unborn child’s development of their brain and nervous system,” Farrugia Randon added.

How does mercury end up in the sea?

Studies show that about half of all mercury released into the atmosphere today comes from the burning of fossil fuels like coal, oil and natural gas, with contributions from waste incineration, mining and other industrial activities.  

This mercury pollution falls directly into the ocean and other water bodies or onto land, where it can be washed into waterways, but in this form, mercury poses little danger because living things can get rid of it quickly.

The problem lies in the fact that bacteria convert mercury as it’s carried down from the ocean surface, turning it into the highly-toxic methylmercury, which is then absorbed by the food chain.

Phytoplankton absorb the substance, and they are in turn gobbled up by zooplankton, which are then feasted upon by small fish and onwards and upwards as the amount of the toxin grows in ever-accumulating quantities.  

As a result, the largest predatory fish in the sea, like sharks and swordfish, can have mercury concentrations in their muscles – the meat of the fish – that are millions of times higher than those of their surrounding habitat, studies show.