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"Aquaculture, not the Internet, represents the most promising investment opportunity of the 21st Century."

- Peter Drucker, Management Expert & Economist


Petuna Seafoods of Tasmania invest in new hatchery from Danish Aquatec Solutions

The original trout hatchery at Cressy, established in the 1970s, was one of the first in Tasmania. It utilized the relatively stable flow of water from the Great Lakes hydro scheme. Until now, salmon smolt had been raised to around 100g in flow-through raceways, but environmental pressures and improvements in recirculating aquaculture systems (RAS) has made the shift from an open system to one that delivers optimal conditions, an economic proposition.

State-of -the-art-hatchery

The new hatchery was designed by the Danish company Aquatec Solutions, with construction supervised by Petuna's infrastructure manager, Kevin Chilman.

He said that nowadays summer water temperatures can reach 23-24ºC in a heat wave, and the new facility has given them a buffer against such adverse conditions.

Selection of hatchery design was critical. The Aquatec system was chosen because of its low water - and power profiles. Daily water intake is 1% of total volume, and the water is cycled through the farm's eight 300m3 tanks every 35 minutes. Peak power use is 230 kW. Most of this is used in the reverse cycle temperature control system, so peak loads are found mainly during summer months.

Water management

Incoming water temperatures from Brumby Creek normally range between 8 and 19ºC. The 100kW heat exchanger runs only to keep the system at a constant 16°. The system itself will add 4-5ºC to the water, just from the friction of the pumps and in the pipes. Kevin has added a heat-exchange system whereby water leaving the facility at 16°C runs across the incoming water which could be 22°C, so a few degrees can be reduced during the 'contact'.

Suspended particulate matter is removed in two mechanical filtering stages. The first comprises three 60µ drum filters, and in the second the drum screen is 18µ. The resulting sludge is flocculated and used off-site as fertilizer.

The recirculating water goes through bio-filtration to remove the organics before being sterilized with ozone. It is then degassed and returned to the system. The stocking rate is 60kg/m3, which leaves them with a 20% safety margin for overage. The concrete tanks are octagonal to reduce the footprint. The shed is fully insulated.

After incubation

After incubation, hatching and first feeding, the fry leave the hatchery at 3-5g. After a further 20 weeks in the nursery growout in optimal conditions they're ready to go to sea at 100g. Kevin pointed out that even through the growout facility was designed to produce 1.5 million 100g fish per year, one of its strengths is flexibility. "We can change our sizes and numbers, and even drop the temperature down a couple of degrees to slow the system if we need to."

Feed conversion is slightly better under the controlled conditions of the indoor tanks. They work on an FCR of 1:1 but have achieved figures as low as 0.89:1. Out in the old raceways, smolt production averaged 1.25:1 FCR with best figures of 1:1, although there have been times when temperatures were too high to feed at all, even with injected oxygen. The new facility has injected oxygen and DO levels are maintained at 100% saturation.

Source: Hatchery International.
See the full article here
Visit petuna seafood here
Visit Aquatec Solutions here

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