Dozens of salmon mortality reports have been used to argue against the industry in Tasmania. 

Tasmania's three big salmon companies reported 68 instances of increased salmon deaths between December 2019 and February this year, according to documents obtained under right to information. 

The holders of salmon farm leases in Tasmania are required to alert authorities when mortalities reach over 0.25 per cent per cage for three or more consecutive days. 

Salmon giant Tassal notified the EPA of increased mortalities on 48 occasions between December 2019 and February 2021.

Huon Aquaculture reported 11 instances of increased salmon deaths, including one in which a worker failed to turn on an oxygen system, resulting in the deaths of around 12,000 salmon. 

Petuna recorded nine incidents.

Most of the information on the cause of the events has been redacted. 

After the state’s EPA released documents to reporters, Tassal accused it of breaching an agreement with the Tasmanian government that restricts the public reporting of mass salmon deaths for months after they occur.

The government has refused to provide reporters with details of this agreement. 

However, its publicly-available salmon portal says mortality reports are updated to the portal in the year quarter after the incidents occur.  

The portal does not include any information about lease numbers or names where mortalities occur, the number of cages involved, the timing or cause of the mortalities.

Local environmental groups say just the details that have been released show several of the areas are not suitable for salmon farming.