Guide to Recirculation Aquaculture: Chapter 8

Chapter 8. Case stories

Figure 8.1 Photo of a recirculation smolt farm in Chile
Bent Højgaard
 

 

Salmon smolt production in Chile

Growth in the Chilean salmon production during the 90s required an increasing supply of smolts from freshwater to be stocked in cages for grow-out at sea. Smolts were produced in river water or in lakes, where the water was too cold and the environment was suffering. Introducing recirculation helped smolt farmers to produce vast amounts at a significantly lower cost in an environmentally safe manner. Also, the optimal rearing conditions resulted in faster growth, which made it possible to produce four smolt batches per year instead the previous one batch a year technology. This shift made the whole chain of production much smoother with a constant flow of smolt being stocked into the cages from where large salmon would be harvested at a constant rate at the right size ready for the market.

 

Turbot farming in China

AKVA group
Figure 8.2 A turbot farm in China.
Kaare Michelsen, Danish Aquaculture
Figure 8.3 A Danish model farm.

Saltwater recirculation is a growing business producing many species such as grouper, barramundi, kingfish, halibut, flounder etc. Turbot is a well suited species for recirculation technology which has been adopted also by Chinese producers. Production results from such installations have shown that turbot perform very well in a completely controlled environment. The optimal temperature for rearing turbot differs with size, and turbot are generally sensitive to changes in living conditions. The elimination of such changes apparently pays back in turbot farming as turbot of 2 kilos can be produced in two years compared to 4 years under normal rearing conditions.

 

Model trout farms in Denmark

Denmark is without doubt the forerunner in environmentally safe trout farming. Strict environmental regulations have forced the trout farmers to introduce new technology in order to minimize the discharge from their farms. Recirculation was introduced by developing so called model fish farms to increase production while at the same time lowering the environmental impact. Instead of using huge amount of water from the river, a limited amount of ground water from the upper layers is pumped into the farm and recirculated. The effect is significant, a more constant water temperature all year round together with a modern facility results in higher growth rates and a more efficient production with reduced costs, investment costs included. The positive effect of the environmental impact can be seen in chapter 6 figure 6.6.

 

Recirculation and re-stocking

Clean rivers and lakes and natural wild stocks have become an important environmental goal in many countries. Conserving nature by restoring natural habitats and re-stocking of endangered fish species or strains is one among many initiatives.

Sea trout is a popular sport fish that occupies many rivers in Denmark, where almost every river has its own strain. Genetic mapping carried out by scientist has made it possible to distinguish between different strains. When the sea trout becomes mature, it migrates back from the sea to its home river to spawn. In the part of Denmark called Funen, rivers have been restored and the remaining wild strains have been saved by a re-stocking programme involving recirculation aquaculture. Mature fish are caught by electrical fishing and eggs are stripped and reared in a recirculation facility. Approximately one year later, the offspring are re-stocked into the same river from where their parents were caught.

FAO Regional Office for Europe and Central Asia
Figure 8.4 Photo from Bosanska Krupa in Bosnia-Herzegovina, where a re-stocking project similar to the one on Funen has been initiated by the help from FAO. The species concerned are Brown trout, Grayling and Danube Salmon.

Different strains have been, saved and in due time the sea trout will hopefully be able to survive by itself in this habitat.

Most importantly this programme has also resulted in a significant better chance of catching sea trout when sport fishermen are fishing from the shores of Denmark. Fishing tourism has therefore become a good earning for local businesses such as hotels, camping sites, restaurants etc. All in all, a win-win situation for both nature and local commercial interests.


Mega farms

The size of fish farms is constantly growing as world production in aquaculture rises. Today, an average sea cage farm in Norway is producing around 5.000 tons of salmon per year, just at one site. In freshwater aquaculture farms are growing in size too, and the fight for space and water is intensifying in a number of countries, especially in Asia.

Also, the environmental impact from aquaculture is causing a growing concern. Recirculation aquaculture offers several advantages that can be beneficial in fish mass production. In some areas sea farms are not popular, and land based farms in the form of recirculation plants are seen as a future way of producing farmed fish. The footprint is low and so is the water consumption. Food safety and control is high, and the output is constant and foreseeable.

AKVA group
Figure 8.5 A 3D drawing of mega farm with 15 meter diameter tanks reaching tank volumes of more than 500 m3 each.

In future, recirculation mega farms will most probably be constructed in order to minimize the environmental impact as well as bringing production costs to a minimum while producing a constant daily volume for the market. Such farms may be placed close to large cities or in areas with high population rates where fresh fish can be supplied readily to consumers.