October is National Seafood Month and this week we’re exploring aquaculture – also known as fish farming – through the lens of sustainability. Aquaculture has been around for centuries and, in some locations, has grown into an unsustainable industry. If, as predicted by the UN, we’re going to increasingly turn to fish to meet the protein needs of our rapidly growing, global population, it’s time to take a fresh look at how we can produce fish in a way that is safe, plentiful and less damaging to the environment.
For many, the fish on our plate is expected to come from fisher folk on their boats, battling the elements and reeling them in from wild stocks. While wild-caught fish is still common (and the last mainstream animal protein resulting from “hunting”), our seafood increasingly arrives from tightly managed aquaculture environments.
Aquaculture has been around for eons, yet it’s often overlooked – even though about half of all seafood eaten in the United States and the world is raised in some type of fish farm system. The proportion of farmed fish consumed is bound to rise as wild fisheries are overexploited and as food protein needs grow to meet the projected growth in global population (and prosperity). (It is estimated that total food supply will need to increase by 70 percent by 2050 to account for this growth.)
It’s also notable that 90 percent of US-consumed seafood is imported, with the rest caught or raised within the country. China is the single-most dominant country in aquaculture, and together with others, like Vietnam and Thailand, Asia is in the lead in production – although other countries lead in species-specific aquaculture, as with salmon production in Norway and Chile. (Learn about the top 10 US seafood species consumed and their source.)
Whether fish are raised in marine or fresh waters, in ponds, rivers, tanks, lakes or in the ocean, aquaculture is adaptable and produces many types of fish and shellfish species for everything from food fish to sport fish to shellfish larvae to fish eggs – and even sea vegetables. In the brief overview below, we’ll take a look at a few onshore (land-based) aquaculture systems and technologies.
Pond aquaculture is when an in-ground pond or collection of ponds is used to raise fish and shrimp, mainly freshwater species, but some marine species as well. Ranging from traditional to high tech, this technique has been successfully used around the world, which means the transfer of local knowledge and structures is well established. Nutrient inputs are lower because of natural cycling through the water and absorption by sediment so pollution can be avoided with good upkeep and management. In some cases pollution from the ponds can contaminate the surrounding surface water when disease-preventing chemicals like antibiotics, waste and excess nutrients enter groundwater through poorly designed or damaged pond beds. Because this is a more “open system,” local conditions from water, air and land use can affect the pond culture and hurt the farmed fish if strong controls aren’t in place.
Integrated Multi-Trophic Aquaculture
Integrated multi-trophic aquaculture (IMTA) refers to farming various species together so that one species’ waste or byproducts can be reused as feed for another species. IMTA join species that need feed, like salmon or tilapia, with species that can sustain themselves from the nutrients released by the waste, such as oysters, clams or kelp. Operators claim such a system can provide more products to sell while reducing waste and problems like algal blooms. While IMTA is primarily in offshore marine settings, more work is being done to bring it onshore.
Aquaponic Systems and Recirculating Aquaculture Systems (RAS)
These are systems that raise fish, vegetables and herbs together, an approach called polyculture, with soilless hydroponics for plants and regular water recirculation to farm fish. The diversity of fish and crops is a unique aspect of aquaponics and RAS that provides self-sufficiency because many of the necessary inputs are inherent to system design. Aquaponics and RAS create self-contained, “closed systems” where a series of tubes move water to tanks that hold it. As fish swim, eat and defecate, the latter provides nutrients to the plants. The plants, in turn, filter the water before it returns back clean to the fish tanks. This system of recirculation can be sustainable on many levels because of its small land footprint and the fact that almost no water is lost in the process. Two inputs – energy and fish food – are potentially problematic, but sustainable solutions are attainable. If pumps and heaters are powered by renewable energy then they avoid burning of fossil fuels and greenhouse gas emissions. Scalability is the biggest question to date.
The bottom line is that while onshore aquaculture is in its infancy, it’s here to stay. We have the opportunity to make fish farming ecologically friendly, which will mean solving riddles like best practices in a given location, how to make fish feed sustainable, harnessing cleaner energy through efficiency and more. Onshore aquaculture is a work in progress with a potentially bright future – time to dive in!