Backing for land-based logic

So believes Steve Summerfelt, Director of Aquaculture Systems Research at the Freshwater Institute in West Virginia.

“I think that, within 10 years, the annual global production for RAS-produced market-sized salmon could reach 100,000-200,000 MT, as highlighted in the recent DNB Markets special report. However, this is hard to know with certainty, because investment over the next five years will be critical to achieve this target,” he tells Fish Farming Expert.

Steve has been working with RAS salmonid projects for close to 20 years.

“Nearly two decades ago, we worked on several of the first viable RAS facilities producing Atlantic salmon smolt in Canada and the United States. And in the decades since, we have continued working with industry suppliers, designers and farmers on RAS that produce market-size Atlantic salmon and steelhead in North America,” he says.

And he feels that the technology available, combined with the growing wealth of experience, and increasing consumer demand for more sustainably-produced seafood makes it an excellent time to be involved with land-based salmon production.

“I think that all US RAS fish producers show special promise, because they can provide a truly fresh and local ‘farm to table’ option at the seafood counter and on restaurant menus,” says Steve.

He is particularly excited by a project, currently under construction, which will combine the production of market-sized Atlantic salmon with the growth of salad plants for human consumption.

“One of the most promising ventures is Superior Fresh, with its integration of salmon and leafy green production for local markets, which looks like it will be the first commercial land-raised Atlantic salmon producer in the United States to go to market with 4-5 kg fish,” he reflects.

And he is looking forward to seeing several other projects begin construction or expansion as the year goes on.

“Atlantic Sapphire and Sustainable Blue tell me that they are currently expanding production, and several new large RAS facilities of 2000-5000 MT/year are close to finalizing financing/permitting/design and expect to break ground in 2017,” he reflects.

Economically viable

Steve is also convinced that rearing salmon in RASs makes economic sense – an assertion he backs up with the findings of a recent journal article.

“I think that it is already economically feasible at the right scale and in the right market. A recent paper by Liu et al (2016) in the peer-reviewed journal Aquacultural Engineering discusses differences in capital requirements and return on investment, as well as carbon and energy footprint requirements for producing market-size Atlantic salmon in land-based closed-containment systems compared to ocean pens. Ultimately, the report found that, at the scale assessed, the cost of producing market-size salmon in land-based farms is roughly the same as that of traditional open net pen salmon farming systems, although the capital investment is higher on land,” he observes.

“It also showed that the carbon footprint of salmon produced in land-based farms delivered fresh to market in the US is less than half that of open net pen salmon delivered from Norway to the US by air freight,” he adds.

Top tips

Although Steve does not believe that there’s only one way to launch successful land-based salmon projects he does have a number of useful tips, which draw on his extensive experience.

He explains: “Some RAS projects have had me concerned, particularly after hearing of water quality problems that appeared and potentially limited salmon growth. I consider the following rules to be key: Atlantic salmon should have water that allows for some light penetration to the bottom of the tank, near 100% oxygen saturation, no more than 12-20 mg/L of carbon dioxide (depending on life stage and other environmental factors), and about 1-1.5 body length per second water velocities in the culture tank. I am still surprised when I occasionally hear of farms where ammonia and nitrite create problems, which is unfortunate because of the vast experience available now on biofilter design. Other concerns are created if processes such as air ventilation, water cooling, wastewater treatment/biosolids thickening, or purging systems are overlooked.”

He also believes that using all-female stock is a useful tool.

He argues: “All-female germplasm is the future for land-raised Atlantic salmon. Our research suggests that mixed-sex Atlantic salmon post-smolt can consistently grow near 400 g each month from a mean size of 500 g to 4-5 kg in freshwater RAS when using 24-hour continuous light and operating with near 15°C temperatures (Davidson et al, 2016; Summerfelt et al, 2016). However, these conditions also result in high male maturation rates that, to date, are barely impacted by photoperiod treatments. We experience excessive male maturation that ranges from 17-38% with mixed sex Atlantic salmon. However, we have always encountered little female maturation. Our current group of all-female salmon are now 1-year-old (from hatch) with a mean fish weight of 356 g and mean gonadal somatic index (ie mass of gonads divided by body weight of fish) of 0.1% with little variation. They will reach harvest size in 12 months; between now and harvest, we will determine what percentage mature. We hope to achieve the same results as when we raised an all-female salmon cohort to 4+ kg in 2009, with only a few percent maturation in freshwater RAS at 13-14°C. All-female germplasm is now commercially available year-round.

“Other farmers report that full strength seawater and cool temperatures both appear to help reduce male maturation when mixed-sex populations are used.”

Moreover, he makes a convincing argument that it’s best to use fresh, rather than salt or brackish water in RASs.

“Our experience has been entirely with freshwater RAS for Atlantic salmon production to market size. Now that all-female eyed eggs are commercially available, I think that use of freshwater RAS is the most cost effective choice for salmon grow-out, which also allows for easier site selection. I think that, occasionally, there have been challenges created when salmonid RASs are built for use with brackish or seawater,” Steve explains.

“Salmon smolts are always produced in freshwater and RAS suppliers have considerable experience now with such freshwater production systems. However, many of the RASs for post-smolt and salmon grow-out are using brackish water, or even full-strength seawater. I think that adapting the salmonid RAS to seawater has sometimes created challenges, as water treatment processes must be larger to account for reduced efficiencies in CO2 stripping, nitrification, and oxygen-holding capacity in seawater. In addition, brackish water and seawater present challenges created by bromide/bromine when ozonating; they also create the potential for sulfate reduction to hydrogen sulfide, which is toxic. Fortunately, it looks like many of the technology suppliers have learned to adapt to such differences, but accounting for these difference still makes brackish/seawater RAS more expensive than a freshwater RAS of similar production capacity,” he concludes.

A longer version of this article will feature in the next issue of Fish Farming Expert magazine.