With fisheries around the world close to or beyond sustainable limits, and current health recommendations advising an increased intake of oily fish to help protect against heart disease, governments are warning that that the only way to satisfy consumer demand is the continued growth of aquaculture.
Fish farms can increase stocking densities and improve yields by up to one third by specifying PSA oxygen applications from Australia-based gas separation specialist Oxair, which can introduce oxygen to fish tanks in its pure form.
The benefits of oxygen generation are well known within the aquaculture industry: fish require at least 80 per cent oxygen saturation in the water for optimal growth. Insufficient oxygen levels cause poor digestion in the fish, so that they require more food and the risk of illness also increases.
Conventional oxygenation methods based on the addition of air alone quickly reach their limits because, in addition to the 21 per cent oxygen that air contains, air also contains other gases, in particular nitrogen.
Applying the same technology as that used in medical facilities, Oxair’s gas generators use pressure swing absorption to introduce pure oxygen directly into the water. This enables the production of much greater quantities of fish in a comparatively small volume of water and causes the fish to grow larger as well.
Oxair CEO James Newell cited one such installation at a barramundi farm in Darwin as example. Results showed that, in that farm, every kilogram of oxygen pumped into the water yielded one kilogram of fish growth.
More efficient to run than traditional paddlewheel equipment, the PSA generators increase the partial pressure and thus the natural saturation limit in the water by a factor of 4.8 compared to aeration with mere air. A steady supply of oxygen is vital, especially since the majority of fish farms are located in remote areas.
With the aid of PSA equipment, fish farms can maintain a reliable in-house supply of oxygen rather than depending upon tanker deliveries which, if delayed, could compromise the quality of a fish farm’s entire stock.
Farms can make further savings as fish health and metabolism are improved, so less feed is needed. As a consequence, salmon farmed in this way will contain a higher concentration of omega-3 fatty acids and develop an improved flavour.
As the quality of the water determines the quality of the fish, the equipment can also be used to create the ozone needed in water recycling reactors to sterilise the used water, which is then treated with UV light before being recirculated into the tank.
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