Why Symbiotic Relationships in Aquaculture Are So Important
If you want your aquaculture system to really flourish, you need more than just fish. Adding other ocean-based life like bivalves and kelp can help create a symbiotic system that is greater than the sum of its parts. Even better, it might end up helping your garden.
When it comes to feeding a hungry world, kelp is on the way. Well, kelp and assorted other items working in symbiosis. These ocean-based nutrients are stronger as a team than they are as solo acts.
It’s very much analogous to the Native American group planting of corn, beans, and squash—known as the three sisters. As the beans grew through the tangle of squash vines and wound their way up the cornstalks into the sunlight, they held the three crops close together and pulled nitrogen from the air to nourish the soil. The leaves of the sprawling squash protected the threesome by creating living mulch that shaded the soil.
In the oceanic version, the whole package is referred to as an integrated multi-trophic aquaculture system (IMTA). It combines the cultivation of fed aquaculture species, like shrimp or fin fish, with inorganic extractive aquaculture items such as seaweed and with organic extractive species such as shellfish and other bivalves. You feed the fish, who feed the bivalves, and the seaweed absorbs the remaining nutrients.
Contrary to monoculture, IMTA takes advantage of organisms functioning at different trophic or nutritional levels to allow one species’ nutrients and by-products to be recaptured and repurposed into fertilizer, feed, and energy for the other crops. It’s age-old, common-sense farming and recycling practices.
“The solution to nutrification is not dilution, but extraction and conversion within an ecosystem-based management perspective where production can be diversified and still remain both environmentally responsible and economically profitable,” says Dr. Thierry Chopin, past president of the Aquaculture Association of Canada and president of the International Seaweed Association.
“It’s a sustainable aquaculture sector, and multi-trophic integration could be the logical next step in the evolution of aquaculture practices worldwide,” he says. “The 1960s saw a ‘green revolution’ on land. The 1980s were the time of the ‘blue revolution’ of aquaculture development at sea. It’s time now to make the blue revolution greener, turning it into a ‘turquoise revolution’ that moves aquaculture to a new era of ecosystem responsible aquaculture.”
While the technology and application of IMTA is decidedly contemporary, the concept isn’t. As far back as 2,200 BC, a Chinese document detailed integration of fish with aquatic plants and vegetable production.
The Chinese also developed a system for growing seven different species in one pond. In 1,500 BC Egypt, hieroglyphic evidence has been found of tilapia being grown in integrated agriculture-aquaculture drainable ponds.
The main difference now is we understand things more like ecology, genetics, and water temperatures. We understand why these things work and how the gears mesh.
Fast forward to today, former president of the World Aquaculture Society and two-time Fulbright scholar Dr. Kevin Fitzsimmons works on a warm water version of Chopin’s caged salmon farm research in the arid Sonoran Desert of southern Arizona.
Where Chopin’s cold climate experiments involve salmon surrounded in concentric circles by hanging kelp, mussels, and oysters, the warm water versions house fish in tanks and ponds where the nutrient-rich detritus ends up helping field crops flourish.
“One of the reasons we got on this kick earlier than most was that we live in the desert where water is so valuable we need to maximize every drop,” says Fitzsimmons. “So, we started aquaculture projects in our irrigation systems, determining what nutrients were coming off shrimp or fish that would support hydroponic vegetables or field crops.”
Fitzsimmons got a chance to introduce a similar program concept in Indonesia after the tsunami of 2004 wiped out the monoculture shrimp farms on the coast of Sumatra. “We outlined a more sustainable way of multi-cropping polyculture—farming tilapia and seaweed with shrimp.
The idea was to look more holistically at the ecology and the side benefits of another crop or two to sell. We were lucky because the basic tambak, or pond, there has utilized a similar system for a thousand years, so it was just a return to something their grandfathers used to do, except with a bit more science involving water quality, nitrogen cycles, and algae blooms.”
Now involved with a United States Agency for International Development (USAID) project in Myanmar, Burma, with a goal of developing more sustainable farming systems involving polyculture, Fitzsimmons says it’s imperative that forward progress be made quickly.
“We’ve been farming the sea, using it as an extraction industry, for a couple thousand years and we can’t keep hunting and gathering out of the ocean on the scale we’ve done because already 50 per cent of all fisheries are either overfished or at maximum sustainable yield,” he says.
Further research is now being done at a university in Abu Dhabi, where an integrated multi-trophic culture grows fish and shrimp while irrigating and restoring salicornia and mangroves.
“We’ve got to do things more efficiently in order to support the number of people we’ve got on our planet now and in the future,” say Fitzsimmons.