When Peter George first set up a community group opposed to offshore salmon farming, it was lucky to get 30 people at protests.
On Sunday at Verona Sands, a remote beach about one hour south of Hobart, some 2000 people voiced their disdain with the industry.
Atlantic salmon farms in Tasmania's southeast are experiencing mass mortality, which in February resulted in 5500 tonnes of fish being sent to waste dumps.
The state's environmental regulator has labelled the deaths unprecedented and is investigating farms and waste facilities for potential non-compliance with regulations.
Vision of Huon Aquaculture workers sealing live fish in tubs has also prompted the RSPCA to investigate and suspend its certification of the company.
Huon and industry body Salmon Tasmania have apologised for the incident, saying it does not represent best practice.
The industry has also pledged to implement "changes" as a result of the mass deaths.
The deaths are because of the disease Piscirickettsia salmonis, which scientists say isn't harmful to humans, as well as warmer-than-usual waters.
Washed-up salmon residue, found at Verona Sands and elsewhere, was found to contain low levels of antibiotics used to treat the disease.
The state's regulator says the level doesn't pose a risk to human or animal health but raises further questions about the antibiotic's presence in the environment.
"There's a lot of concern and a lot of anger," Mr George said.
"In the last 10 years it has gone from 'you're lucky to get 30 people on the beach' to getting (the numbers) yesterday.
"It is so clear now that a large number of people ... are not prepared to tolerate what our industry does in our waters anymore.
"That becomes anger when they see their beaches being polluted."
Mr George, who founded Neighbours of Fish Farming, is running as an independent at the upcoming federal election in the seat of Franklin, held by Labor.
Author Richard Flanagan urged people to make their thoughts known at the ballot box.
"We want to make this a federal election issue. You can't be anti-salmon and vote Liberal or Labor," he told the protest.
Salmon farming is also under the spotlight at Macquarie Harbour on Tasmania's west coast.
Licences in the harbour are being reviewed after a challenge by conservationists who want to safeguard an endangered fish.
Tasmania's governing Liberals and Labor opposition support the salmon industry, which the government says directly employs about 2000 people.
Both parties at federal level have said they want it to continue in Macquarie Harbour.
Premier Jeremy Rockliff said he believed a "great majority" of Tasmanians supported the industry.
