Study to help tuna export business

Mercury levels in tuna fish examined:

Ramani Kangaraarachchi

Malinda Weththasinghe

Malinda Weththasinghe is a final year student of the Uva Wellassa University. He is an animal and nature lover since his childhood. An old boy of Matara Rahula College, he developed a very useful research related to fishing industry in the country, which is the distribution of mercury in tuna fish (Thunnus albacares) in Sri Lanka in relation to its habitat and size.

He believes that since the mercury levels in tuna fish may determine the future of tuna exports to EU countries, further research on this aspect needs to be considered seriously.

Reduction of mercury levels through value addition and reduction of discharge of mercury into the sea by the industries may help to sustain the industry.

Mercury is an element having different forms and is toxic to human beings. Mercury is used in many industries for different purposes and released to the environment with industrial wastage.

Mercury gets into waterways through waste disposal and ultimately ends up in the sea where element mercury is converted into organic mercury due to microbial action.

When this happens there is a possibility of fish absorbing the mercury through bio-magnification.

Mercury gets accumulated in the human body due to consumption of such contaminated fish and may have serious health problems.

Therefore, the EU market has imposed regulations regarding the levels of mercury in fish.

However in Sri Lanka, research regarding mercury levels in tuna fish has not been carried out yet.

This research is aimed to find the mercury distribution in tuna in relation to the landing sites, different locations of the body of yellow fin tuna.

The study was conducted in four landing sites; Galle, Trincomalee, Dondra and Negombo.

It has revealed that there is a significant relationship between the landing site and mercury level of fish.

Eastern coastal areas recorded higher mercury levels than the Western coastal area.

The mean mercury values are shown in the figure below.

According to the graph Dondra and Trincomalee recorded higher mercury values than Galle and Negombo.

Dondra recorded the highest mercury level.

This may be explained well considering the flow of oceanic currents as shown in the figure below.

The mercury released into the Indian Ocean by the highly industrialized south eastern countries may flow to Dondra area with the East Indian oceanic current.

Sometimes mercury which is deposited in the Bay of Bengal also comes through the East Indian Ocean current.

Therefore the east coast area in Sri Lanka shows high mercury levels than the west coast.

The study also revealed that the mercury levels increase with the increase of body weight in fish but there are no specific locations in the body of the fish where they get accumulated. The samples taken from different locations in the body (head, under the pectoral fin and tail) showed the same level of mercury.