Farmers stocking dams with trout the latest diversification for Buxton Trout & Salmon after coronavirus hits tourism

Mitch MacRae has had to deal with everything nature can throw at a farmer, and perhaps a little bit more, because his pernickety stock simply die if the water temperature gets above about 24 degrees.

Buxton Trout & Salmon, which lays claim to being Australia's first commercial trout farm, sits astride the Acheron River near Marysville.

The chilly water fed by Lake Mountain and the Yarra Ranges makes it, the Snowy Mountains and Tasmania, among the few places in Australia that suit rainbow trout year-round.

That's because, in the densities need to keep commercial quantities, the fish virtually stop growing in water temperatures of more than 22 degrees.

As the heat builds, oxygen levels fall and their ability to convert feed into protein - usually a remarkably efficient 1:1 ratio - falls away dramatically.

"Where you can actually farm trout successfully is limited," Mr MacRae said.

"And in the last few years, with increasing water temperatures, we've seen the industry start to really struggle with a few farms shutting down, so it's actually retracted a bit in the last few years.

"The trout in Australia are starting to become more resilient than trout in cooler countries, so over time the species has adapted a little bit, whether it can keep adapting, I don't know, we'll see."

Nevertheless, Buxton Trout & Salmon hasn't been immune and fire turned up the heat even more.

Water temperatures climbed after the Marysville fires denuded the nearby hills, stripping the Acheron of shade.

It's had a dramatic impact but Mr MacRae has adapted by radically changing the very nature of his business. It's now every bit as much a tourism venture as a fish farm.

"We've geared ourselves around more and more away from being a straight production farm into a sort of a tourist farm," he said.

The farm had always been open to the public but, as production fell, he built barbecues and a nice big natural-looking fish-out spot and began selling fishing experiences.

"Tourism became a bigger, bigger part of the business in the last 10 years as we refocused in that direction," Mr MacRae said.

"We effectively get about half the production that I had 10 years ago but we've maintained the same sort of turnover by selling directly to the public."

Turning his attention away from wholesale markets, Mr MacRae now sells fish to local restaurants and wineries as well as direct to the public at the Queen Victoria Market.

"You try and have a variety of income streams to cover yourself; when the tourists are quiet, you still go to the markets to sell to and vice versa," he said.

"It spreads the risk a bit."

But the coronavirus lockdown has slashed Buxton Trout & Salmon's tourism turnover by 80pc and Mr MacRae is once again refocusing his business, selling wood-smoked fish and caviar directly as well as helping farmers stock their dams.

"Farmers stocking up their dams has been a huge thing in the last couple of months, with people wanting to get a bit self-sufficient," he said.

"People putting in veggie gardens are stocking up all their dams with trout as well."

While difficult to farm commercially in less than perfect conditions, rainbow trout are much more robust in the lower densities used to stock farm dams, Mr MacRae said.

"If you're stocking a farm dam, you want to have at least a couple of metres deep water so there is some cool water in the hot spells," he said.

"You won't stock them in the same sort of density as what what we can do with the running water coming through but, usually in a decent sized farm dam, you can still put in your 100 trout.

"Obviously, you don't want any weed chemical runoff, pesticides or too much fertiliser or anything like that.

"As long as it's nice and open without too many cormorants and it's not right in the middle of a paddock where it's going to get fried over the summer, the trout will be fine."

Another option is to set up a backyard aquaponics system, which Mr MacRae said had become very popular.

"People put in a veggie garden and a fish tank and pump the water backwards and forwards between the two," he said.

The rainbow trout are sold in different sizes, including young fish about five centimetres long or 20cm long.

The 20cm fish would likely be plate size this summer, Mr MacRae said, and were easy to manage.

"We put them into plastic bags and pump them up with oxygen and they'll sit in the backseat of your car for a few hours but, once you get over about 10 inches long, they get a bit trickier to do that way," he said.

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