Thursday, March 28, 2024

We Studied Mercury Levels In Cape Monkfish Off Namibia’s Coast

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By Victoria Ndinelago Erasmus & Johannes Angala Iitembu

The presence of mercury in the marine environment is becoming an issue of concern. Once in the ocean mercury is converted into a more toxic compound known as methylmercury. In this form it’s absorbed by the digestive tract of creatures at all feeding levels in the marine ecosystem. In fish, reduced swimming activity, loss of balance, and possibly death have been linked to mercury contamination. Mercury has a very low rate of breakdown and excretion, which means it builds up – in a process known as bioaccumulation – through the entire food chain.

We conducted research to establish the levels of mercury in Cape monkfish, a commercially important fish species off the Namibian coast. This species also plays a key ecological role in the marine ecosystem. It feeds on other fishes and so regulates various fish populations.

The two conditions in which we found higher levels of mercury concentration were in larger fish and in fish in deeper waters. Some fish (0.57%) had higher levels of mercury above the World Health Organisation limit of 0.5mg/kg. However, most of the fish had mercury levels still below the World Health Organisation limit of 0.5mg/kg.

Our findings are important because although the Cape monkfish isn’t currently a risk to humans who eat it, this may change because of future industrial development in the region.

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