As we head into 2025, this year’s monthly article series will focus on an industry that accounts for more than half of the seafood consumed around the world: aquaculture. Aquaculture, or in the very simplest of terms – raising aquatic flora and fauna for food in what are essentially water farms, has been in practice for several millennia.
Aquaculture science and innovation is always changing, and to date, there exist four major types of aquaculture: Recirculating Aquaculture Systems, Fish Cage Systems, Inshore-Nearshore Cage Farming, and Offshore Cage/Sea Farming.
This month we will be focusing on Recirculating Aquaculture Systems (RAS). This aquaculture system is fully sealed off from the environment; think like a huge fish tank! These huge containers replace the natural flow of water with a recirculation and filtration system. Because of this, RAS can be sited on land, as opposed to needing to be off-shore.
Every method of supplying humans with seafood has an environmental impact. These impacts are not necessarily better or worse than another method, but all are different, and all need careful management.
One of the benefits of RAS is that due to it being entirely isolated from the natural habitat, there is extremely low risk of escapes or disease transmission to the wild fish populations. As the tank conditions can be entirely controlled, it has the advantage of almost guaranteed high-quality fish, with a reduced need for antibiotics and protection from nature’s unpredictable forces like unfavorable weather conditions, external pollution, and predation.
Unlike other aquaculture methods, with RAS there is much flexibility in where it can be placed. Farms can choose to be located closer to other industry plants or consumers, thus lowering the economic and environmental footprint caused by the need for transportation. On the other hand, the constant recirculation and filtration required to ensure good conditions for the fish uses a great deal more energy than other aquaculture methods which utilize the natural flow of water.
When constructing a RAS, a significant factor for location is determined by where the waste will go. Here in Maryland, RAS systems are not currently in operation but will likely be built in the very near future. In 2022, the Norway-based company AquaCon wanted to build a salmon RAS system in Federalsburg, Maryland, but ended up scrapping the project due to pushback on its proposed waste management. They had proposed discharging their waste water into Marshyhope Creek, which is the only known Chesapeake Bay spawning ground for endangered wild Atlantic sturgeon.
As of this past Fall of 2024, AquaCon began trying for a new location in Port Deposit off the Susquehanna River at a former naval training site. This proposal has been received generally more favorably by fishery ecologists, as the waste water discharge would be diluted by more than 1,000-fold in the Susquehanna as opposed to Marshyhope Creek. AquaCon Maryland LLC also intends to get the majority of its water directly from the Sesquehanna, as opposed to groundwater, as was initially proposed for the rejected site in Federalsburg. This would mean that the water would have to be purified before it can be used to raise salmon, but the discharge would theoretically be cleaner than what was pulled from the river.
RAS are rarely small, and as with any large construction project, concerns over controlling stormwater runoff and nutrient pollution remain questions to be considered.
If you’re curious about seeing a recirculating system in action, the Institute of Marine and Environmental Technology in Baltimore holds an annual open house. This includes a tour of their Atlantic salmon recirculating system in their Aquaculture Research Center.