There are calls for the Environment Protection Authority to stop the operations of a waste processing plant in the Derwent Valley, after thousands of fish were found dead at the Salmon Ponds.
Last Wednesday, more than 120,000 fish including brown and rainbow trout were found dead at the popular tourist spot in the upper Derwent Valley.
A putrid smell was also reportedly coming from the Plenty River.
Ken Orr from the Shooters, Fishers and Farmers Party thinks the waste processing plant has contributed to the mass kill, and is urging the EPA to act.
"Between about 12:30 and 1:30 last week the Plenty River was contaminated, and unfortunately the Salmon Ponds is on a flow-through system with the Plenty River."
"This shouldn't happen. The Salmon Ponds is a 154 year-old heritage site, and has upwards of 40,000 visitors from tourists a year.
"I want the plant shut until they've put a risk mitigation program in place that satisfies not only the EPA, but also the peoples of Tasmania."
"Tasmanians are the owners of the Salmon Ponds and we want them there for future generations."
The EPA was alerted to the incident when it happened and says it is investigating.