Ocean trout and saltwater char

Ocean trout and saltwater char

Justin North
6 recipes
Published by
Hardie Grant Books
Steve Brown

Small steps to a big business

The word ‘Petuna’ is a combination of the names of Peter and Una Rockliff, whose fishing empire was born almost half a century ago. Peter, who had always loved fishing and spent childhood holidays at the coast with fishermen, had worked hard on the land to buy his first boat, Alva, a 25-foot long seasonal vessel with an open hull.

During the spring of 1949 Peter travelled to Bridport on Tasmania’s north-east coast in search of fishing opportunities. There he met Una and they married soon afterwards. The couple’s next boat was Rowana, a 32-foot vessel with a tiny cabin and by 1954 Peter was fishing full-time for cray. He would be at sea for up to ten days at a time and, in the days before radio contact, this was difficult for Una and their three children.

Peter took his first crewman during the 1960s, fishing for scallop and shark around Tasmanian waters, and in 1971 finished building the Petuna. She was large, sturdy and had the capacity to venture further from the shore than previous vessels, enabling the Rockliffs to discover unfished cray grounds.

Later the Rockliffs built the Petuna Enveavour, Tasmania’s first trawler. At this time trawling as a fishing method was still largely unknown. The number of trawlers operating in the area leapt from one to sixty in a short time as fishermen discovered it allowed them to bring in huge numbers of fish, and to travel farther from shore than before. Trawling attracted its fair share of criticism, however, and was blamed for the overfishing of certain waters and damage to the sea floor.

The couple began to investigate aquaculture as an alternative, and in 1991 Petuna bought a 50 per cent share in Sevrup Fisheries in Cressy, south of Launceston.

Over the years the company has cultivated salmon, golden trout and saltwater char, as well as developing a superior strain of ocean trout, a species now synonymous with the name Petuna.

Petuna’s produce is processed at the Devonport factory. In pristine conditions ensured by strict decontamination procedures, fish are cleaned, filleted and packaged for distribution throughout Australia and international export. There is also an onsite smokehouse. With the airport only minutes from the factory, it is possible for Petuna fish to be served in New York restaurants a mere 48 hours after leaving Tasmanian shores.

Although their son-in-law, Tim Hess, now oversees the daily running of the business, Peter and Una Rockliff remain hands-on at Petuna, and in 2004 were awarded the Order of Australia medal for their contribution to the fishing industry.

A hatchery on the hillside

Kevin Chilman and his wife Josie work at the Sevrup Fisheries hatchery, breeding and grading salmon and ocean trout, readying them to be transported to sea pens in Macquarie Harbour, near Strahan, where they grow to full size.

At Sevrup, Chilman’s chief responsibility is maintaining brood-stock quality in order to produce fingerlings (tiny fish of only a few centimetres) of consistent number and quality. They are capable of producing 650,000 fingerlings annually for transfer to sea cages. To meet this demand, five million eggs must be incubated in the hatchery every year.

Ocean trout spend five weeks in incubation before hatching, and Chilman ensures direct contact with UV light is avoided in the incubation pens, as the light can penetrate the eggs and kill the fish. Once hatched, the fish sink to the bottom of the tanks, feeding from the egg’s yolk, which remains attached to the body for around eight weeks after hatching. When the yolk is consumed, the hatchling rises to the water’s surface in search of food.

The first solid the fish consumes is a formula containing vitamins, proteins and fats. The formula is made locally at Cambridge, which has established itself as a centre for development in marine biology. Isolated strains of algae are also cultivated in Cambridge for use in the hatcheries.

The fish are theoretically ready for transportation once they reach a weight of 120 grams, but are kept at the hatchery for up to a year for rigorous grading. At the time of our visit, 80,000 ocean trout were being held in an outdoor pen, awaiting grading and their final journey to the sea pens, where they spend another year to eighteen months.

Grading is a time-consuming procedure: each fish is inspected individually for any defects. Size and colour are also checked, and any fish that don’t make the grade are sold to farm dams to be sold locally. This is a costly but necessary elimination process. According to Chilman the market is becoming more and more particular and the grading ensures that only the finest quality fish make their way to the grow-out pens and eventually to market.

A salt- and freshwater fish

The process of moving fish from a freshwater environment to salt is known as ‘smultifying’; a young salmon going through this transition is referred to as a ‘smult’. World Heritageprotected Macquarie Harbour, where the fish are grown in sea pens, is a mixture of freshwater on the surface and saltwater beneath, a result of the Franklin and Gordon rivers flowing through the harbour out to sea.

As the salmon, trout and char mature, each fish moves instinctively to an area where the salinity is optimal for its own needs. The darker freshwater towards the surface also serves to protect the fish from direct sunlight that causes discolouration. These conditions are ideal for maturing fish in the salmonid family – water that is too saline can cause disease in immature fish gills.

In Australian aquaculture, in order to produce fish all year round, the conditions of the spawning period are synthesised, tricking fish into spawning during the Australian winter as well as in summer.

Macquarie Harbour is known for its penal settlement, Sarah Island, which was used by the government between 1821 and 1832 to house its most dangerous criminals. The now deserted 11-acre island can be seen from the sea pens just off Liberty Island, nine miles out from Smiths Cove where a Sevrup office and net restoration workshop are situated. The sea pens are each weighted with anchors around the circumference of the pens to prevent tidal flow dragging the enclosures and reducing their volume. In twenty metres of water, the seven-metre pens house thousands of fish each. Divers work in the pens twice a week, clearing out any dead fish and monitoring the state of the nets. The lease agreement with the government also dictates that Petuna is responsible for cleaning the sea floor beneath the pens.

Fish are harvested onsite: they are removed and bathed in carbon dioxide which stuns them. By the time the fish regain consciousness, they have been cut open and die rapidly in water aboard the harvesting vessel, before being placed in an ice slurry which keeps the flesh at a temperature of 2°C. Allowing the fish to regain consciousness is a deliberate tactic as their final movements hasten the expulsion of blood from the body. Once in ice, the fish are moved back to land and shipped to Devonport for further processing and then transport around Australia and abroad.

Petuna has recently established a new breed of saltwater char. Also known as Arctic char, this fish is indigenous to northern waters towards the Arctic Circle, and was first commercially fished during the 19th century off Labrador. It is caught in freshwater streams or farmed in saltwater for differing flavour. This versatility also affects flavour; char raised in saltwater yields a deeper coloured and sweeter tasting flesh than its freshwater cousins.

Recipes in this Chapter

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