Almost 10,000 tonnes of farmed salmon died across two months during an unprecedented mass mortality, prompting a renewed call for further scrutiny.
Tasmania's salmon industry apologised in March after a spike in deaths at pens in the state's south due to a bacterial outbreak and fish matter washed up on beaches.
Some 3395 tonnes of fish died in pens statewide in March, according to the latest data from the state's environmental regulator.
This comes after more than 6300 tonnes died in February, with the combined 9695 tonnes comprising about 13 per cent of Tasmania's annual farmed salmon production.
The Environmental Protection Authority has declared the unprecedented mortality event over, noting fish deaths had declined by almost half.
"Water temperatures are falling and there has been a significant decline in the number of pens above the mortality reporting thresholds in April," the authority's chief executive Catherine Murdoch said.
Laws requiring salmon farms to report death tonnage to the regulator, which then makes the numbers public, have only recently been implemented.
The regulator said it was unable to provide data about the tonnage of deaths prior to February, while industry body Salmon Tasmania has been contacted for comment.
The Greens renewed calls for a parliamentary inquiry, saying more information needed to be made public.
"Ten million kilograms of dead fish equates to around 2.5 million mature Atlantic salmon that have suffered a cruel death," Greens leader Rosalie Woodruff said.
"However, the (regulator) can't or won't provide an accurate breakdown of which leases these deaths occurred within, or even which region of Tasmania they occurred in.
"The unchecked outbreak of disease throughout Tasmania is a biosecurity disaster of unprecedented scale in modern history."
Water monitoring no longer detects antibiotics used to treat the disease, the regulator says.
Huon Aquaculture, one of the companies caught up in the mass mortality, was stripped of its RSPCA green tick after video captured workers sealing live salmon in tubs with dead salmon.
The governing state Liberals and Labor opposition support the industry.
The mass mortality event was "really traumatic", Environment Minister Madeleine Ogilvie told state parliament on Tuesday.
The regulator says it will continue to receive and monitor data and will publish mortality weight information quarterly.
