The main cause of death of the thousands of herring that were found dead in Kolgrafafjörður, West Iceland, two weeks ago and have continued to die since, is lack of oxygen, according to preliminary results of the Icelandic Marine Research Institute’s testing.

Archive photo by Páll Stefánsson.

However, the incident may have been caused by a combination of factors, such as a low ocean temperature, visir.is reports.

The preliminary results indicate that close to ten percent of the herring in the innermost part of the fjord was killed, 25,000-30,000 tons.

The herring has now left the area where the oxygen level was low but the decomposition of all the dead fish in the fjord may maintain the condition and so all fish that enter it in large quantities in the coming months are at risk of being killed.

The Marine Research Institute will continue to monitor the herring in the area and the environmental conditions in the fjord.

According to the news on radio station Bylgjan, the condition was caused by a landfill and bridge across Kolgrafafjörður, constructed in December 2004.

The oxygen level in the inner fjord is thought to have dropped significantly when the large school of herring entered it.

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ESA

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