Aquaculture: Farming Sustainable Seafood for the Future

Aquaculture: Farming Sustainable Seafood for the Future

The commercial seafood industry has put enormous pressure on fisheries, decimating entire species within recent history. While much progress has been made toward sustainable management of the fisheries that remain, aquaculture ( Learn moresustainably.   
Aquaculture is the farming of seafood – fish, but also shellfish – in controlled, captive conditions. At present the U.S. produces only a relatively small amount of its seafood with domestic aquaculture ( https://www.fisheries.noaa.gov/insight/understanding-sustainable-seafood ), importing far more from overseas. 
In fact, over 91% of the seafood Americans consume is imported ( https://blogs.ei.columbia.edu/2016/04/13/making-fish-farming-more-sustainable/ ), much of it from China and other parts of Asia. Fish farming is ancient in China, and today 88% of the world’s aquaculture takes place in Asia. 
Not all aquaculture methods are equally sustainable. The need to feed farmed fish populations has led to the overharvesting of forage fish. 
Farmed fish populations in the ocean can lead to pollution in the form of fish waste and leftover food, which can cause oxygen depletion in the water. There are also concerns about farmed fish escaping into the wild and compromising the gene pools of wild species. 
However, other approaches are possible. Land-based closed systems eliminate many of the environmental issues associated with fish farms. There are still concerns about wastewater and about sourcing feed, but many aquaculturalists are getting better. 
For example, take companies like VeroBlue, an innovative business founded on a family-owned farm in Iowa. The Nelsons are a third-generation Iowa farming family, and several years ago they took to raising hundreds of thousands of barramundi, an Australian fish said to taste like red snapper ( https://www.motherjones.com/environment/2017/01/barramundi-aquaculture-fish-farm-iowa-veroblue/ ). 
Barramundi may be the ideal farmed fish: every pound of them costs one pound of grain and up to seven gallons of water, compared with six pounds of grain and 1,800 pounds of water for beef. They are hardy, adaptable, and tolerate crowding well. 
The Nelsons are environmentally conscious, too: they treat wastewater by extensive filtration and use a beneficial bacteria-based process to convert excess ammonia into nitrates. The wastewater goes on to help irrigate the crops, and it does not pollute – the nitrates are too diffuse for that. 
Farmed barramundi also have much lower requirements for fish meal than farmed salmon. VeroBlue uses pellets made by the company Skretting, which recently announced a new feed that has no fish meal. 
The Nelsons are not alone: the movement for sustainable land-based aquaculture is gaining ground (literally) elsewhere. 
Recirculating systems, in particular, are emerging as a key innovation to boost sustainability since the water can be used and reused for immense savings. In fact, these systems use 100 times less water per kilo of fish than traditional land-based systems. 
Another advantage of recirculation systems is the way they allow for the water to be monitored continuously. With continuous monitoring, the risk posed by disease becomes less, and there is also less need for antibiotics. 
Take Denmark-based Hallenbaek Hamburg for example, this company farms rainbow trout (Oncorhynchus mykiss) using a recirculation system that can reuse more than 96 percent of its water. The wastewater is subject to treatment to remove nitrate, and the sludge produced from the cleaning process is used to produce biogas or fertilizer. 
Salmon and some trout populations (steelhead, for example) are anadromous, meaning they are born in fresh water but then spend much of their lives at sea before returning upriver to spawn. This has traditionally meant raising them in fresh water and then relocating them to the sea to raise them in sea cages, with all of the aforementioned issues pertaining to fish farming in the sea. 
However, recirculation systems are solving these anadromy-associated problems too, by allowing farmers to carefully control salinity as well as temperature. 
One such system has been developed by scientists at the University of Maryland Department of Marine Biotechnology. This system has achieved a 99% water recycling rate. The wastes it does produce are filtered through microbial communities, and it produces methane as a biofuel.  
The system allows for regulation of water temperature, lighting, and salinity levels. By achieving the proper environmental regimen and by feeding the fish a special pellet to mimic reproductive hormones, the designers at the University of Maryland have been able to get the fish to reproduce in predictable cycles. 
Barramundi, salmon and trout are not the only seafood to be sustainably farmed in this manner. The company RDM Aquaculture is farming saltwater shrimp in Indiana. It has recycled the same water for five years, producing zero waste and using no chemicals. 
RDM’s secret is its heterotrophic biofloc system, which allows all of the organic matter, including the shrimp wastes, molted shrimp shells, dead shrimp, bacteria, and microalgae to stay in the water. This means the shrimp have plenty to eat – microalgae – and the bacterial colonies can process all waste. 
Another key innovator is Thierry Chopin, a University of New Brunswick professor of marine biology. Chopin’s insight was to combine species from different parts of the food web, something known as integrated multi-trophic aquaculture. 
Chopin placed blue mussels and kelp below salmon pens, downstream, allowing the mussels to eat salmon wastes and the kelp to absorb minerals and nutrients. Sea urchins and sea cucumbers are also part of the system: they consume larger particles on the ocean floor. 
Paradoxically, another approach to aquaculture is moving aquaculture pens out into the open ocean to take advantage of ocean currents that can keep the farms clean and help eliminate sea lice and other parasites.  
These innovations demonstrate the progress that is being made toward sustainable seafood in the realm of aquaculture. Increasingly, designers and farmers are finding sustainable answers that demand less of nature and give more back.   

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