LITHUANIA
The shrimp are grown using biofloc technology. A variety of microorganisms are present in the water maintaining its quality, providing nutrition for the shrimp, and combating pathogens.
Biofloc technology is economical but finicky to operate The farm uses a unique hybrid RAS system, and in contrast to a system that has biofilters and UV and ozone treatment for water purification, Local Ocean developed a unique biofloc technology (a method of producing beneficial microorganisms). Local Ocean’s biofloc produces an array of beneficial microorganisms that plays a role in maintaining the water quality in the tanks, providing a source of nutrition for the shrimp, and competing with pathogens to prevent their levels from increasing to the point where they pose a threat to the stock. New nutrients are then produced from the unused 40
feed and the waste produced by the shrimps and these nutrients are either used directly by other organisms or are converted into new microbial biomass which can be consumed again by the shrimp reducing the need for feeding. The action of beneficial bacteria in the biofloc keeps compounds in the water like ammonium at levels that are not toxic for the shrimps, so that the water in the system does not require replacement or recirculation (only 10-15% water loss per cycle). In addition to the benefits of the biofloc for the shrimp production, the biofloc systems developed by Local Ocean also offer economic advantages as they are much cheaper to build and operate than a traditional RAS. However, because the water is a
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living medium full of all kinds of microorganisms including fungi, protozoans, rotifers, nematodes, copepods, and microalgae in addition to bacteria, it is more difficult to optimise. As a result, the water in each tank has a unique set of bacterial parameters and is kept independent of all the other tanks. This separation keeps the system biosecure so that in case of a problem with the water in one of the tanks, the issue is confined to that tank and is not spread across the whole system. Both the biofloc and the shrimps consume oxygen, so the water must be aerated constantly. The slightest disruption to the aerating systems can cause mass mortalities so the company has not one but
two backup systems to ensure the water is always properly oxygenated. Keeping the growing units independent of each other, allows the company to experiment with the water and the systems in different ways to find out what works best for shrimp growth. This has revealed two or three directions that yield very good results with high yields (currently over 10 kg of biomass per sq. m) and low mortalities (less than 25% loss from the post larvae stage). Most interesting is that the limit does not seem to have been reached, says Mr Legrand, so we are still increasing the density and producing more shrimp per sq. m than in the previous cycle, so there is still scope to develop and optimise further. A production cycle takes 3-4 months
