Fish farms have fallen under criticism as sources for pollutants and disease which threaten the fish and ecosystems in areas where they are used. This is particularly true for saltwater species, whose water requirements generally mean farming them in the open water or near the sea.

What if we could farm saltwater fish miles inland, entirely in tanks, producing almost no waste? It sounds like a fish tale.

<img src=“http://www.ars.usda.gov/is/graphics/photos/feb09/d1227-2i.jpg” width=200 style=“float:right; margin:0 0 10px 10px” alt=“Scientists and inland seafood”>But US scientists are working towards doing just that. Research funded by the U.S.D.A’s Agricultural Research Service is working out the kinks on farming cobia and pompano, two sought-after seafood fish, hundreds of miles from the sea in massive tanks that are almost fresh water, at just 5 ppt salinity instead of 35 ppt of seawater. Their recent success in raising juveniles in these conditions is a huge step towards sustainable aquaculture for

The researchers used an aquaculture method called a "recirculating aquaculture system” (RAS) which has the potential not only to rear fish miles inland, but in a cost efficient and waste-reducing way. The system is closed, meaning it’s almost entirely self-sustaining, generating as little as 3% of less of the total water used every day as waste. This water could be treated for use on land, to water crops or artificial salt marshes. All the fish waste caught in the filtration system can be made into compost or even as source of biofuels, making the system one of the greenest fish farming practices to date.

<img width=150 src=“http://www.ars.usda.gov/is/graphics/photos/feb09/d1229-5i.jpg” style=“float:left; margin:0 10px 10px 0” Alt=“Scientists and their Pompano larvae”>But, it’s never been used successfully for saltwater species. The salt in the water makes the system horribly inefficient, and generally raises costs so much that it’s not worth the effort. ARS scientists, though, have successfully cultured two saltwater species in only 5 ppt salinity. If they can continue succeeding in their efforts, RASs might just allow us to raise any kind of fish anywhere we want, reducing our pressures on the oceans and allowing fish stocks to rebound.

A RAS system therefore solves the two worst problems with fish farming – the waste water pumped into the environment and the threat of spreading disease to local species. If research like this makes saltwater RAS systems efficient and successful, and if we can grow high-demand seafood products in these systems, we just might be able to have truly sustainable seafood without having to severely cut what we eat – which would be really, really good news to all us seafood lovers out there.

images c/o USDA