Tasty, versatile, and rich in essential omega-3 fatty acids: salmon is one of the most popular edible fish of all. Shops sell fish caught in the wild, but their main produce is salmon from breeding farms which can pollute rivers, lakes and oceans. Just how big is the problem? German and Chilean scientists are working to answer this question under the leadership of the Helmholtz Centre for Environmental Research (UFZ). They examined the dissolved organic compounds which enter Chile's rivers from salmon farms, and have published a report in the journal Scientific Reports, warning that these substances are placing huge strain on ecosystems and are changing entire biological communities.
Tasty, versatile, and rich in essential omega-3 fatty acids: salmon is one of the most popular edible fish of all. Shops sell fish caught in the wild, but their main produce is salmon from breeding farms which can pollute rivers, lakes and oceans. Just how big is the problem? German and Chilean scientists are working to answer this question under the leadership of the Helmholtz Centre for Environmental Research (UFZ). They examined the dissolved organic compounds which enter Chile's rivers from salmon farms, and have published a report in the journal Scientific Reports, warning that these substances are placing huge strain on ecosystems and are changing entire biological communities.
Salmon lead a fairly varied life. The adult fish live in the sea but swim upstream into rivers to reproduce and lay their eggs in gravel beds in the upper reaches. This is where the young hatch, grow for a while in the clean, oxygen-rich water, and then set off towards the sea. To breed the popular edible fish, farmers have to provide different living conditions depending on the age of the fish.
Chilean fish farmers base their approach on the natural life cycle of the salmon. In the clear rivers which flow from the central ridge of the Andes towards the Pacific, they have installed a few hundred hatcheries for the eggs and the youngest animals. Slightly larger salmon live in cages in the lakes of the South American country, and the adults then move into similar accommodation anchored in the sea just off the coast. In 2012, Chile’s aquacultures used this method to produce some 820,000 tonnes of salmon with a total value of just under five billion US dollars. For years, the country has been ranked second behind Norway in the list of key salmon producers worldwide.
However, this has not been without an impact on the environment. The cages for the medium and larger fish leak excrement, food residue and other substances into the country’s seas and coastal waters. The companies also draw water for their hatcheries from some of the extremely clean, natural rivers. They pump it through the tanks for the young salmon before reintroducing it to the river further downstream - where it is certainly not in good condition.
Read more at Helmholtz Centre For Environmental Research – UFZ
Photo: Salmon aquaculture on Río Niltre, a small river in Chile. The youngest generation of salmon is bred here. The waste water is conducted into the river through a pipe (centre of picture). (Photo Credits: Norbert Kamjunke)
