Europes oldest RAS houses sustainable eel

For the Valencian eel producer, EU requirements demand several hundred thousand small eels are released each year. Strict requirements for emissions apply. For fish welfare oxygen levels are always maintained.

The RAS plant outside Valencia was started up in 1986 and has been in full operation ever since. The annual production is 400 tons of eel, with an average weight of more than 150 grams. A third goes to the domestic market, while the rest goes to other EU countries, especially the Netherlands, Italy, France and Portugal

- We have developed the RAS technology over the years, says Rodolfo Barrera, director of the company Valenciana de Acuicultura, S. A. in Puzol north of Valencia.

According to Barrera eels are well suited to RAS facilities. Other species have also been produced, in seawater and freshwater, such as sea bream, sea bass, sturgeon, tench, tilapia and arapaima, as well as aquarium fish. Supermale (YY) populations of Nile tilapia are also maintained for breeding.

When Mr. Barrera acquires wild fingerlings, there are however strict EU requirements on how to proceed. To comply with regulations, several hundred thousand small eels are released each year into waterways where eel populations are reduced. 

- We believe in sustainable aquaculture and we are environmentally conscious. We also meet extremely strict requirements for our emissions. A complete water treatment plant is responsible for it
s purification using activated sludge. All waste is managed according to the environmental compliance program.

Oxygen supply is fundamental. Maintaining optimal oxygen levels is part of fish welfare. To keep fish alive in a sunny country, new diffusers are now being installed. A total of two thousand meters of oxygen diffusers are now being installed in 200 shallow breeding tanks.

Efficient oxygen addition under such conditions is difficult. An important requirement for choosing this diffuser design is because of its high number of very small holes per square centimetre. 

Rodolfo Barrera, director of the company Valenciana de Acuicultura, S. A

- The small holes provide maximum efficiency generating a multitude of fine bubbles. We have seen that the holes do not block over time and the tube maintains flexibility. We have experience with EPDM, and we know that neither the eel nor the characteristics of our water spoil this type of material, says Barrera. 

For the renewal of our diffuser system, Barrera looked to Norway. 

- We have designed a model for this plant that we have carefully tested for efficiency and effectiveness before shipping a sample batch. After weeks of testing, the diffuser was approved. We see that different species and operating systems each require their own solutions, says Nils Hovden from Bio Marine in Surnadal, which has provided the diffusers to Valenciana.

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