Better utilization of water in charr farming / Efficient rearing systems for Arctic charr




Ragnar Jóhannsson, Helgi Thorarensen, Ólafur Ögmundarson

Supported by:

Technology Development Fund

Better utilization of water in charr farming / Efficient rearing systems for Arctic charr

The need for water in aquaculture is extremely high and what ultimately limits the size and production capacity of aquaculture establishments is access to hot and cold water. The aim of the project was to test a cheap and simple way to reduce water consumption in charr farming. At the beginning of the project, it was assumed that water could be used in charr farming four times better than is currently the case. However, it turned out that the water can be used seven times better. The result of this study is that it is possible to produce around seven times more biomass in aquaculture on land with the amount of water used today. The goals of the project were therefore achieved and much better. In order for this to be possible, the following things need to be kept in mind:

• It is very important to release turbidity from the water as soon as possible. Therefore, a drum filter is a necessary equipment and all the water must be filtered with each cycle of recycling. The filter should use 100 μm cloth, which cleans all particles that can reduce the efficiency of the farming system.

• There must be sufficient current in the fish tanks and it is desirable that the water exchange rate is not less than 45 minutes to ensure self-cleaning and to satisfy the oxygen demand of fish at high concentrations.

• A bio-cleaner is a necessary equipment when the recycling is greater than 0.03-0.05 L kg ‐ 1 ∙ min ‐ 1. It releases ammonia from the broth. The biocleaner used in this study has been shown to work well and its design has been patented

Aquaculture requires large volumes of water are required for aquaculture and the size and production capacity of fish farms is in most places ultimately determined by access to water and geothermal heat. The objective of this project was to reduce water requirements in Arctic charr aquaculture. Through simple reuse of water the plan was to reduce water requirements fourfold compared with standard reference values in Arctic char fish farms in Iceland. This goal was achieved and at the end the reuse was sevenfold. The conclusions of the project are that by using the same amount of water used today and with a simple reuse of it the annual increase in production of Arctic char can be sevenfold the annual production of today. But to make that possible, the following points have to be kept in mind:

• It is necessary to minimize the turbidity in the water by all means. A drum filter of 100 μm is therefore needed in the recirculation system.

• The current in the rearing system has to be sufficient and the water change ratio should not be less than 45 minutes to secure self-cleaning and to fulfill the oxygen need of the fish reared in high density.

• A bio filter is needed if the recirculation exceeds 0.03-0.05 L kg ‐ 1 ∙ min‐ 1. It phases out the ammonia in the rearing system. The bio filter used in this project has shown that it works and the design of it has a patent

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