23 October 2016
Salmon farming poses a threat to marine ecology and also raises some food safety issues, environmental activists say. Photos: Bloomberg
Salmon farming poses a threat to marine ecology and also raises some food safety issues, environmental activists say. Photos: Bloomberg

Salmon farming: Health and environmental issues

There has been a lot of debate about food safety issues surrounding salmon, especially the farmed variety. It will be good if we devote some time to learn more about the health, as well as the environmental aspects, related to salmon farming.

Amid dwindling catches in the oceans, fish farming was seen as a way out by many countries, both in terms of securing food resources and to alleviate the ecological pressure on the seas.

But the truth is that aquaculture, rather than reducing the pressure on the oceans, has been blamed for posing a threat to the environment and wild fish stocks.

Salmon are carnivorous. Raising one ton of salmon would require three to five tons of forage fish, which would speed up the depletion of wild stocks in the oceans.

In the year 2008, around 23 percent of the world’s marine fish catches were ground up and fed to farm-raised fish. With a rapid decline in small wild fish, feed input costs have risen, pushing farmers to look for cheaper alternatives such as meat, bone meals or even fermented manure as fish feed.

China, Vietnam, Bangladesh and India have started using dregs composed of feces as fertilizers for fish culture.

Intensive salmon farming features the use of open-net cages. Each cage can hold up to 50,000 marine creatures. With such high density, diseases and sea lice are easily spread among the farmed fish in the waters.

While sea lice can be got rid of when wild salmon enter the freshwater from the ocean, the farmed salmon have to depend on heavy use of chemicals. As the water is subjected to excessive chemical treatment, the fish output and the meat quality suffers.

Open-net cages built at the mouth of the rivers or bays, meanwhile, are spreading sea lice around, causing significant decline in the wild salmon population. Wild salmon from Pacific Canada and Scotland, for instance, are believed to be victims of intensive fish farming.

Transnational corporations were said to have spread Infectious Salmon Anemia (ISA) virus to Chile and North America from Europe. Though virus-carrying salmon will not sicken humans, the industry has been using tremendous amount of drugs to prevent the fish from getting the disease.

The situation, however, could result in the farmed fish containing a high amount of antibiotic residues.

Given that Hong Kong has imported salmon of both kinds from different locations around the world, one hopes that the Food and Environmental Hygiene Department and the Consumer Council will offer citizens more information on the safety of salmon available in the local markets.

This article appeared in the Hong Kong Economic Journal on August 2.

Translation by Darlie Yiu

[Chinese version 中文版]

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Columnist of the Hong Kong Economic Journal

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