Australia Weather News

As far as salmon escapes go, the mass breakout of almost 300,000 fish isn't the biggest.

"The one at Snake Island was big, we got a lot of fish there but I'd say this would be in the top five," fisherman Dave Dennison said.

The fish, in numbers estimated between 260,000 to as many as 600,000, were set loose after wild weather hit southern Tasmania on May 11.

Enclosures which hold salmon numbering in the hundreds of thousands broke free from the site near Bruny Island, later found washed up along the Tasmanian coast, along with other fish farming equipment owned by salmon company Huon Aquaculture.

Dave Dennison and his mate Brian McMichael are not wasting the opportunity. Like many others, they have taken to the southern waterways in pursuit of the fugitive Atlantic salmon, the species farmed in huge numbers around Tasmania, not native to the area.

The pair have netted 40 of the fish since the breakout and have come back for more.

"I've caught a lot over the last 20 odd years ... I had some very good escapes down here," Mr Dennison said.

A long-time fisherman, Mr Dennison brought his boat down from up north earlier in the month betting the weather was going to turn nasty, a knack which has paid off for him in the past.

"I knew there'd be a lot of salmon out, by instinct," he said, adding it was the "bad weather, southerly to south-east gales, which bring about catastrophe".

Mr Dennison was a commercial fisherman for 45 years, before giving it away four years ago, and said it was a waste of time going after the farmed salmon with a rod.

"You won't get many on a rod and line, they are uncatchable, but they are catchable in a net," he said.

"They don't know how to feed themselves properly, except for the feed they get in the cages, that makes it very hard."

The salmon are industrially hatched in captivity in their thousands and transferred to increasingly larger tanks before being put into open water pens.

Swimming inside nets made from the same material used to make bulletproof vests, the Huon Aquaculture salmon are kept safe from marauding seals and other predators.

Fed at regular intervals on a pelletised mix of vegetables, fishmeal, protein concentrate, vitamins, minerals, amino acids and pigment to bring about the pink flesh colour, meaning the fish don't know how to forage or hunt.

Research has also found a majority of farmed salmon are deaf, due to the nature of industrial production.

Big bad world awaits fugitive fish

Dr Jeremy Lyle, from the Institute for Marine and Antarctic Studies, tracked what happened when 30 salmon were released from a farm in Macquarie Harbour on the state's west coast.

Most died within three months, the rest starved to death or were eaten by sharks, seals or caught by anglers.

Dr Lyle said some of the salmon managed to survive by swimming back under fish farm pens to scrounge uneaten pellets that fell through nets and dropped to the bottom of Macquarie Harbour.

"They really don't thrive," he said.

"Fishermen will notice in this current case that their catch rates will start to drop off fairly rapidly, that's partly due to dispersal and partly due to the fact they're being caught, they are being predated upon."

Advocacy group Environment Tasmania has been campaigning against fish farming in Tasmania.

Laura Kelly said the study in Macquarie Harbour should be replicated in the south near Bruny Island, following the latest escape, to monitor the species impact on native fauna.

"The latest research from overseas shows that salmon being top end predators do travel extensive distances and feed quite voraciously on native fish," she said.

Dr Lyle agreed it would be useful to know where the escaped salmon are headed.

He invited those catching escaped fish to contact the Institute for Marine and Antarctic Studies in Hobart, with details of where and when they made their catch.

Mr Dennison said the fish could be as far away as Melbourne by now.

"They swim at 1 kilometre an hour and they've been swimming for a fortnight, that could represent 800 kilometres," he said.

'Everyone gets a salmon'

Asked if there was the usual culture of secrecy around the best Tasmanian fishing spots, Mr Dennison was non-commital.

"I won't get involved in the politics of it," he said.

He said the salmon escaping benefitted many, not just those who pulled them from the water.

"Tackle shops, people making nets, fishing gear, selling outboard fuel, repairers, everybody gets a share of the catch," he said.

Besides that, "people are using their boats and having a good time".

Mr Dennison said he might venture out again in piscatorial pursuit, but the weather was turning and Tasmania's winter was on the way. And, news had got out.

"There'll be a lot of boats out on Saturday, it'll be crowded."

Despite all that, he admitted he probably had at least one more salmon mission in him.

"Salmon are a good gift to people, and a lot of fun catching them," he said.

"They die of starvation in the finish, so it is better if we and everybody else can net a few ... everyone gets a salmon for free."