Shellfish
BY NICKI HOLMYARD
Better together Combining different species in one site is an old idea, given a new twist
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newly-released report by EUMOFA, the European Market Observatory for Fisheries and Aquaculture Products, looks in part at the past, present and future of integrated mul�-trophic aquaculture (IMTA) in the “Blue Economy”. In IMTA systems, species from different trophic levels are raised in proximity to one another. The waste stream from fed species, such as fish, become nutrients for others. For example, filter feeders like mussels, clams, cockles and oysters, take up the fine par�culate material, while plants like kelps take up the dissolved inorganic nutrients. In addi�on, deposit-feeding species such as cucumbers and sea urchins can be raised directly underneath a farm, to take up larger par�culate organic material. As a result, IMTA reduces the ecological impacts of fish farming opera�ons, by ac�ng as an environmental remediator. It can also improve social percep�ons of aquaculture, and provide financial benefits for producers through product diversifica�on, faster produc�on cycles, and price premiums on IMTA products. Although the concept of IMTA has been around for millennia, the phrase “integrated mul�-trophic aquaculture” was first introduced in 2004 by its Canadian champions Dr Thierry Chopin and Dr Shawn
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Shellfish.indd 28
Below Left: Tiger prawns Opposite: Sugar kelp;
mussels; cockles; sea cucumber
Robinson. According to Dr Robinson, IMTA is “a reasonably complicated way of just saying ‘mixed farming’.” The pair were awarded the 2009 Research Award of Excellence of the Aquaculture Associa�on of Canada, which recognises excep�onal, innova�ve research contribu�on and commitment that has a significant impact on aquaculture industry development in Canada. The EUMOFA report tells us that IMTA has progressed from the land-based co-culture of fish and rice in China, which can be seen in surviving clay models of rice fields and aqua�c life da�ng back 2,000 years to the late Han period, to the concept of holis�c aquaculture introduced in the 1970s, and the more sophis�cated concepts of today. References to the use of different trophic levels in aquaculture for remedia�on of nutrient overloads or addi�onal produc�vity date from the early 1970s, and IMTA was a reality in China in the 1980s. China is the world’s largest producer and consumer of fish, shellfish and seaweeds, and is o�en used as a model for the applica�on of IMTA. The country has more than 50 major bay systems, and 10 million hectares of coastal waters, 1.3 million hectares of which are suitable for inshore mariculture and IMTA. Sanggou Bay is the most important and best known example of integrated mul�-trophic aquaculture. IMTA exists in three forms in China: incidental, transi�onal and engineered. Incidental is the most common form, and occurs when extrac�ve species and fed species are farmed in the same semi-enclosed bays, as a coincidence of aquaculture expansion, leading to the natural assimila�on of waste. Transi�onal systems are set up inten�onally with species from different trophic levels to supplement overall farm produc�on, while engineered
www.fishfarmermagazine.com
11/01/2021 15:00:27
