Fish farm fire sets 52k salmon free in Tas

Some 52,000 farmed salmon have escaped into the wild after an "inexplicable" fire at a fish pen in Tasmania.

The blaze broke out at a Huon Aquaculture farm in D'Entrecasteaux Channel south of Hobart on Monday.

"We are estimating that we have lost between 50,000-52,000 four kilogram fish," Huon Aquaculture CEO, Peter Bender, said.

An investigation into the fire, which damaged a third of one pen above and below the waterline, is ongoing.

"We have electrical equipment on our pens but in 35 years of farming we have never had an electrical fire on a fish pen so the cause has baffled us," Mr Bender said.

The company has informed wildlife and environment authorities in Tasmania.

Citing a 2018 Institute for Marine and Antarctic Studies report on escaped farmed fish, Mr Bender was confident the mass escape won't harm native animals.

"Farmed salmon generally don't appear to feed on native species as they are typically used to feeding on fish pellets," Mr Bender said.

"Escaped salmon typically don't last long, unfortunately, what the seals don't get, the fisherman quickly do."

In mid-2018 wild storms damaged several Huon fish pens in southern Tasmania, setting hundreds of thousands of salmon free and giving many recreational anglers a meal.