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RAS fish swims

Explained: What is RAS Aquaculture?

May 24, 2021

Aquaculture is an innovative industry – it doesn’t stand still for long. Fish farming has traditionally been done in either ponds or sea cages – in fact this practice goes back many millennia.

It is still the case that the vast majority of farms today are of this variety – what are sometimes known as net pen or semi-closed farming systems. But over the past few decades, as aquaculture has rapidly expanded to provide over half of the seafood consumed around the world, it has also frequently innovated and introduced new practices. One of these has been the introduction of closed systems – more commonly known as RAS, which stands for Recirculating Aquaculture Systems.

What are these systems? As you may have guessed from the name, they are sealed off from the environment and replace the natural flow of water in a sea or a lake with a water filtration and recirculation system. As a result, they can be placed on land – and if so they might be referred to as land-based farms.

RAS Farm Netherlands
Fish schooling on a RAS farm, as they do in the wild

Different Methods, Different Impacts

So is this a better way to farm? At ASC we don’t usually like to make sweeping generalizations, and won’t make an exception here because the fact is it depends on how a farm is managed. Closed, semi-closed, and net pen systems are simply different ways of producing farmed seafood and each has certain impacts that need to be managed carefully and responsibly. That’s where ASC comes in.

In the case of RAS, one of the benefits we have already mentioned is that there is more flexibility where a farm can be sited. Farms could be located closer to where consumers are, lowering the economic and environmental costs of transportation. But there is a flip side to that – in many areas or countries land and water are in short supply, so taking a farm out of the water and onto dry land can have other impacts and drawbacks.

Another potential advantage is that RAS farms greatly reduce the risk of escapes or disease transmission to wild fish population by tending farmed fish in a completely separate area.

RAS farmer
A RAS farmer in the Netherlands carefully feeds fish

On the other hand, there are certain areas where closed systems are likely to be more impactful. One example is energy use. Constantly recirculating and filtering water to ensure conditions remain right for the fish requires much greater energy than the natural flow of water utilized by pen systems. At a time when we are all thinking more about the carbon footprints of every aspect of our lives, including the food we eat, this is important to consider. It’s worth noting that even if farmed on land, seafood still has a low carbon footprint compared to most other animal protein and the energy source used by the farm, whether it is renewable or not, will make a big difference to its impacts. But this is still an impact that RAS farmers need to think about more than other fish farmers.

New ASC Requirements

While RAS farms still represent a small minority of the aquaculture industry, their use is growing. ASC works hard to reflect the always innovative nature of the industry by adapting its standards and program to reflect the most recent changes. For this reason, we have been working on new requirements that will apply specifically to RAS farms. While many of the impacts will be common to all aquaculture, issues like energy and water use, and effluent disposal, are different for RAS farms, so specific requirements are needed. Farms will need to meet these requirements in addition to the requirements in the relevant species standards –for example, a land-based seriola farm will be audited against the ASC Seriola Standard as well as the new module of RAS requirements.

Like all ASC requirements and updates, these have been developed with our stakeholders’ input and advice through an open public consultation. The feedback we have received has been used to finesse the requirements, which are now being finalized for launch.

RAS fish swims

The requirements are interim rather than permanent. Another recently concluded public consultation is looking at the environmental requirements of a new aligned Farm Standard. This will cover all ASC certified species, and will allow ASC to adapt the program efficiently to new developments while retaining the robust nature of the ASC standards. The Farm Standard will also integrate specific RAS requirements, so when this goes live it will replace these interim requirements.

In the meantime, ASC will continue to keep an eye out on the latest trends in aquaculture so that farms can be assessed on their individual performance against the most robust standards in the global aquaculture industry.

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