Originally established in 1949 as a fishing company, Petuna Group diversified into aquaculture in 1990 with salmon farming. Although it is the smallest in Tasmania, the company is the largest domestic retail supplier of salmon in Australia. Petuna is dedicated to ethical and sustainable practices earning it the top-tier Best Aquaculture Practice (BAP) 4-Star Accreditation. From a state-of-the-art hatchery recirculation system using less than 5% of the water used in traditional hatcheries to marine farms stocked at some of the lowest commercial stocking densities in the world, the company’s operations exemplify its dedication to environmental responsibly.

Over the past 20 years, Petuna’s Rowella marine farm grew from two circular pens to thirty ‘pieced together’ 24-meter pens. With improvements in fish health, operational ability, and mechanical advances, it became obvious the farm would greatly benefit from a complete re-design. This project was not as simple as it may seem. The farm is in the Tamar River, which has considerable tidal flow, and fed from the ocean creating a harsh marine environment. The new system would need to withstand the tidal forces and be protected from corrosion. The tides only allowed a 6-hour window for the removal of the old pens and installation of the new ones. If the pen was not moored off prior to the tide turning, the farm structural integrity would be significantly compromised. Additionally, the site location has minimal flat hard standing ground with tight truck access and construction area.

With a business revolving around the salty ocean, Petuna is no stranger to corrosion. Numerous protective coating systems had been used over the farms evolving life, but none have been more successful than hot-dip galvanizing. Based on this knowledge, Petuna specified galvanizing for the walkway frames and small components such as lugs and fittings. At a size of 12m x 3.5m, the walkways were too large for the local galvanizer to handle. The components had to be shipped from the manufacturer in Launceston, TAS to a galvanizer with a larger tank in Melbourne, VIC and then back to TAS creating a logistical challenge that required daily communication.

Even with the larger galvanizing kettle, the walkways required a progressive dip. With a critical timeframe, construction and installation had to stay on schedule to ensure minimal disruption to the working fish farm while still working around the tides. Teamwork between the galvanizer, fabricator and Petuna was paramount for this project and its successful completion is evidence of the strong working relationship developed between all parties.

Sustainability and fish health are imperative to Petuna’s business model. As a growing market, salmon farms will require refurbishment and/or expansion. Hot-dip galvanizing, which is safe for both the fish and flowing river water, extends the life of their pens, reducing the number of raw materials needed to replace obsolete structures.