Abalone divers, mussel farmers, conservationists and the Tasmanian Greens have raised concerns about ocean fish farms in Tasmania's south.

All four groups believe not enough is known about the impact of salmon fish nets on underwater ecosystems in the D'Entrecasteaux Channel and Storm Bay.

Salmon producer Tassal wants to combine two of its D'Entrecasteux leases into one, with plans for 28 cages.

The Marine Farm Planning Review Panel met in Hobart to hear environmental concerns.

Abalone Council spokesman Dean Lisson wants more research into the environmental impact.

"We have concerns about the level of sedimentation from salmonid waste, we have concerns about their net cleaning practices and what happens with the bio-fouling after they've cleaned their nets," he said.

"The abalone industry has had concerns now for a number of years about the salmon farming practices in the lower channel.

"That's what it's all about, it's about keeping our waterways healthy and maintaining sustainability for all the industries - all of the recreational fishing, the commercial fishing, the aquaculture."

Local mussel farmer Warwick Hastwell said salmon farming practices had put him out of business.

"They have ruined it, we've had to basically close my doors and lay my staff off," he said.

Mr Hastwell, whose lease is 150 metres downstream of Tassal's main farm at Dover, believed the in-water cleaning of the salmon pens resulted in his mussels being smothered by orange tunicate, an invasive invertebrate.

"We call it 'orange snot' because it's basically like a big, orange jelly smothering everything that studies show is caused by fragmentation," he said

"And directly upstream from me I've got an industry that's fragmenting, and dispersing into the water column. Coincidence? Maybe."

Calls for more research into impacts of salmon farming

Mr Hastwell wanted research into whether Tassal's fish cages were responsible for the contaminant.

"There should have been more research done before they embarked upon this process of in-water net cleaning," he said.

"I've been put out of business by these practices, but my concerns go beyond my business.

"There's issues here with the broader environment that need to be addressed."

In a statement, Tassal's head of sustainability Linda Sams said the company was looking into Mr Hastwell's concerns, but stressed sound science underpinned its business.

"The Tassal site he is referring to is not used as a main grow out site and is used sporadically to temporarily hold fish and is empty now."

But Environment Tasmania spokeswoman Rebecca Hubbard said authorities were consistently failing to address concerns about the impact of nutrients on other marine species, as well as noise and odour pollution.

"There seems to be a systemic failure with the assessment and management of salmon farms in Tasmania," she said.

Sorry, this video has expired Expansion of salmon farm industry questioned ( Selina Ross )

Ms Hubbard called for a halt on all salmon farming expansion until a review looked at how it was assessed.

"All of these stakeholders are being sidelined for one industry - the salmon farming industry - when there are really big questions around environmental impacts and impacts on other industries," she said.

Tasmanian Greens Leader Kim Booth agreed, comparing ocean-based fish farms to pig sties and saying fish farming should be done on land.

Mr Booth called for a moratorium on all fish farm expansions, pending further research.

"Ocean-based fish farming - the way it's done in Tasmania - is particularly damaging to the environment," he said.

"We should be farming these fish in a smart way, which is what they do overseas - increasingly, they're moving to land-based fish farms."

Government is reviewing concerns

Primary Industries and Water Minister Jeremy Rockliff expressed full confidence in the Marine Farming Planning Review Panel's handling of any expansion proposals.

He said the link between salmon farming and damage to abalone or mussels had yet to proven scientifically.

Professor Colin Buxton has been engaged to review existing research in response to the abalone industry's concerns.

"Professor Buxton is currently reviewing this matter and is expected to submit a report on his findings in the first half of this year," the minister said in a statement.

The department and I will continue to work cooperatively with all aquaculture and fishery industries on these issues."