by Vaughn Entwistle, Managing Editor, International Aquafeed

 

Recycled Aquaculture Systems (RAS) have been around for more than twenty years. Mostly they are used in hatcheries, although the economics are changing and now many RAS systems are used in mainstream fish farms.

In 2018, our magazine visited Les Poissons du Soleil (fish of the sun) located at Balaruc Les Bains, France to see their state of the art RAS fish farm facility. We were given a thorough tour of the impressive facility by Mr Dolé Martin, the Production and Logistics Manager for Wellboat Expeditions.

 

Sur la mer

Upon arriving, one of the first things that struck us about Les Poissons du Soleil was its coastal, 'sur la mer' location, as the two main RAS tank buildings are located right on the shore of the Mediterranean. Being located so close to the sea offers a fish farm facility a number of important advantages.

'We pump water directly from the Mediterranean,' Martin explained. 'All the water is treated. We pump and treat approximately 100 cubic meters of water an hour. Each of our two buildings has its own filter system. The water is first run over the primary sand filters. It is also run through biofilters.

'UV filters, supplied by the Marseille company BioUV, and drum filters are supplied by Faivre. The biological filter takes the ammonia out of the water which is recycled and returned to the tanks. The big particles are taken out by the Faivre drum filters.'

The ability to have a free supply of water is invaluable, but there are complications, as Martin explained: 'The water pumped from the Mediterranean varies in temperature according to the season. In the winter, the water must be heated to at least 18°C to ensure a good growth rate in the fish. We try to maintain a temperature of between 18°C and 25°C throughout the year.'

Martin explained that fish are more active in the warmer summer water, and consequently consume more fish feed. 'We have to manage all these parameters in our growth predictions,' Martin added.

 

Two hall facility

The Poisson du Soleil facility is divided into two buildings, which mirror one another in their layout. Each building houses 12 tanks for a total of 24. Each tank holds 40 cubic metres of water. Martin explained, 'Because we are so close to sea level here the tanks are tall, but not very wide. As the water circulating through the tanks passes the pump it is injected with oxygen to around 500ppi.'

The Poisson du Soleil facility grows mainly Sea Bass and Sea Bream. They receive stock from their two hatcheries in France and then grow the fish until they reach a specific size/weight.

'We receive the sea bass at 1.5 grams,' Martin said, 'we grow them to 5-10 grams, and then sell them to fish farms all over Europe. These fish farmers then grow them to around 300 grams—it depends on the market they serve. We send a lot of fish to Tunisia where the fish might be grown to 200 to 250 grams, because the customers there like to buy five fish per kilo to feed the family.'

 

Money in the tank

'In a tank like this, we put in between 100,000 to 500,000 fishes. Usually we work 20 to 30 kilos per cubic metre. We have the capacity to have 70 kilos per cubic metres with good feeding, good oxygenation, and good water quality, but we don't reach this biomass by security.'

A tankful of fish represents a large capital outlay, so Poisson du Soleil takes precautions to safeguard each tank using a system that alarms in the event of an emergency.

'The pump is alarmed,' Martin said. 'The temperature of the water is alarmed. And we have a sensor inside that measures the oxygen content of the water.'

 

Automated feeding

The Balaruc Les Bains facility relies upon a computer-controlled feeding system.

Martin explained that the company is having great success feeding the sea bass a new feed formulation: Introplus NT 15 manufactured by Biomar.

'With our computer-controlled feeding system, we can feed at the rate we want. Our technicians check the fish's average weight, to make sure the computer is growing the fish at a good rate.'

 

Fish and ships

When the fish reach the correct weight for shipping, they are loaded either into a ship or onto a truck. Because of its proximity to the Mediterranean, ships are able to dock directly alongside the facility, which greatly simplifies things.

'We are very close to the sea,' Martin said. 'So, our boats can dock here and do the transfer using gravity from the RAS tanks to the boat. What is important in our process is that we do not touch the fish with a net.

'The fish, from the bottom of each tank, are pumped through a fish pump to the sorting machine and come back through gravity using a tube that runs through the centre of the room. The boats are loaded directly from the RAS tanks', he continues.

Loading the trucks is carried out in a similar fashion. 'Using tubes, we fill each chamber in the transport truck. The trucks go to Spain, Croatia, Greece, and Italy. After the truck has been loaded with fish, we add cold water at 10°C because the colder the water the more docile the fish are. The tanks are loaded to a 70 kilos maximum density. The truck can then be sent all over Europe with good water quality and docile fish.'

Martin then added that Poisson du Soleil's location in central France makes it easy to ship the fish all over Europe. 'We are located at the crossroads of East and West highways so we can send the fish to Southern Italy or Southern Spain. Likewise, we are located at the crossroads of North/South highways which allows us to send the fish to Northern Europe.'

The company ships about 30 million fish per boat per year. Of the remaining fish, about 25 percent is sent by truck. The majority go to Tunisia or Algiers. Fish from other farms are also sent to Poisson du Soleil to be sent by boat.

'On one boat,' Martin said, 'we can load about 1-1.5 million fish with a biomass of 10-to-15 tonnes and we do approximately 30 trips per year.'

 

Difficulties transporting fish by truck

By truck, you can have many problems transporting live fish. It is best to send the fish by boat. You can pump the water and change the water all the time, plus the fish are in the midst of being acclimatised, and when the fish arrive you can unload the fish directly into the farmer's cages. Just one transfer from the boat to the cage, is much better for the fish.

The fish are then pumped into a tank. They pass through the sort machine and are counted into three different sizes. After, they can go back into the tank according to their size.

'The growth rate is different for each fish, so we grade them in order to provide the customer with a batch of fish that grow at the same rate. We guarantee size and we take out all deformities. We have to sort the fish every two-to-three weeks. At the moment we have 3.5 million fish and approximately 30 tonnes of fingerlings.

 

Efficient staffing needs

Compared to cage net fish farms, RAS facilities can often get away with far fewer staff.

'We have about six staff, although we usually have two people on the rented boat used to transport the fish to Tunisia. Two days there, two days back and half a day to unload. 250 cubic meters. We always need some empty tanks, because we are always cleaning tanks.'

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