The major Norwegian salmon producers have seen approximately $5.6 billion (€5.8 billion) wiped off their cumulative market value following the government's announcement of a surprise new tax on the industry.

The government proposal on Wednesday to increase taxes on salmon and trout farming by 40 percent is causing uproar and confusion across the country's salmon farming industry, but also sent stocks of the main listed players crashing.

The proposed tax, which must still be approved by the Norwegian Parliament, would take effect beginning in the 2023 tax year and will be applied to volumes above 4,000 or 5,000 metric tons.