Earlier this year, Huon Aquaculture announced reduced dissolved oxygen levels in Macquarie Harbour on the west coast were slowing the growth of its fish.

Jeff Ross, a senior research fellow at the Institute of Marine and Antarctic Studies (IMAS), said an exceptionally hot summer in Tasmania had affected waters across the state.

"Particularly in the south of the state, the water temperatures have been particularly warm," he said.

"Things are already starting to cool down now."

Mr Ross said salmon were sensitive to warmer or colder weather.

"Temperature is a pretty important variable for growing salmon, absolutely."

In a statement to the Australian Stock Exchange (ASX), Tassal said it would withdraw its tenders for the Coles supply contracts in order to optimise returns.

Growth 'in line with forecast expectations'

Tassal managing director Mark Ryan said Macquarie Harbour on Tasmania's west coast provided fish during summer, and now the company was harvesting fish from the south-east, where numbers were down.

"While it is true the west coast has experienced an unseasonably hot and dry summer this season, overall mortalities and growth were in line with forecast expectations," he said.

"Dissolved oxygen levels and temperature were the main husbandry challenges on the west coast for Tassal this summer, but these were managed effectively allowing the company to continue strong levels of supply during the summer and the key Easter period.

"Tassal is now harvesting fish from the south-east, which has 75 per cent of the company's stock, and this is where there is now a material reduction ... available for supply.

"These are the new season fish that Tassal is harvesting, and they experienced record water temperatures. Despite this, survival has been solid."

More industry transparency needed

Tasmania's Resources Minister Jeremy Rockliff said the salmon industry would continue to expand.

"These are natural conditions and individual companies within the salmon industries need to make their own decisions with respect to investment opportunities that they make," he said.

"We have a very highly regarded, adaptive management regime when it comes to our salmon industry in Tasmania."

Tasmanian Greens Senator Peter Whish-Wilson repeated calls for more transparency from the industry.

"This is a significant matter of public interest, and the impact on fish growth is not just an issue for the salmon companies and their profits and shareholders, but it's also an issue for Tasmanian communities around the salmon farms, the recreational fishery as well as the broader ecosystem," he said.

Read the full story by Emile Gramenz at ABC News.