Integrated Multi-Trophic Aquaculture (IMTA) may be in our future but is actually a throwback to how some countries farmed fish on a small scale in ancient times. In some places it continues today. IMTA however, according to the National Oceanic and Atmospheric Administration (NOAA) is, “An evolving approach to seafood production that emphasizes an ecosystem management approach where ‘fed’ species, such as finfish or shrimp, are farmed in close proximity to species that can ‘extract’ nutrients from the water column, such as shellfish and algae or seaweed.”
This can be a model for a smaller isolated farm that is inland from a natural waterway or as described in the April 2015, issue of Scientific American in an article by Erik Vance, “Fishing for Billions”, implemented on a grand scale at Zhangzi Island and several other islands, near Korea. These islands are being used for a grand IMTA experiment.
Instead of deploying neighboring cages that are used in most of the world, most notably in Canada’s Bay of Fundy, the Zhangzidao Company that is conducting the fish farming, according to the Scientific American article, uses entire islands. After having “carefully studied the movement of nutrients along the shores….they seed nutrient-rich parts of the islands with young scallops bred to thrive here while carefully removing their predators.”
Critics argue the IMTA of the Zhangzidao Company is not legitimate because there are no finfish being raised which theoretically would feed the shellfish with their excrement. These farms however produce 60,000 tons of kelp, 200 tons of sea urchins, 300 tons of oysters, 700 tons of sea snails, 2,000 tons of abalones and 50,000 tons of scallops each year. The company references detailed island maps showing ocean currents, where nutrients congregate and where yields are highest. They have also used 20,000 refrigerator sized concrete blocks to form needed artificial reefs.
Critics of IMTA rightly point out that where finfish are raised today there is net segregation of farmed fish from wild fish. They state however that this separation is inadequate because finfish escape and breed with wild fish. They observe that in open-ocean or bays some of the dangers of fish farms are still present. Specifically, there is still the presence of sea lice and various diseases that can infect the area. They also are critical of IMTA because it has not shown yet that it has the ability to scale in inland, artificial environments.
It is a reality that the oceans are being over fished. This large-scale use of the open water around islands is probably not possible in and around most industrialized nations because of too many environmental laws, political pressures and the lack of public acceptance.
Unfortunately fish are appearing in much smaller numbers and are migrating to different environments as a result of climate change. In addition, melting glaciers and the future absence of run-off streams due to global warming will eliminate many spawning grounds. Something may need to be done if our world population continues to grow and increases its demand for fish as the protein source in its diet.
What is attractive about IMTA is its mimicry of the natural interdependence of multiple species in an ecosystem. Its use is far cleaner for the environment and “green” by comparison to traditional farming techniques.
We salute the pioneers of IMTA as a model to be perfected and put to productive use around the world. While it may not produce the same amount of fish the ocean now holds, it may serve as a necessary substitute for the wholesale fishing now conducted by too many nations.
Use the following links to gain more information or access the original source documents used for this article.
http://wn.com/integrate_multi-trophic_aquaculture (watch film[s])