Integrated Multi Trophic Aquaculture (IMTA)

Integrated Multi Trophic Aquaculture (IMTA) 

Introduction:

Populations around the world face questions of food security today on a scale that has not been seen in recent human history. The evolution of how we feed our populations and the technologies we use to do it have created a unique set of circumstances that bring with them unique challenges, and despite significant advances in food production and our knowledge of food nutrition and food safety, hunger continues to millions of people around the world. It is thought that over a billion people in the world are currently undernourished (World Food Programme, 2010). 

Concept of Integrated multi-trophic aquaculture (IMTA):

Integrated Multi-Trophic Aquaculture (IMTA) is a concept for culturing multiple species on one aquaculture site that has the potential to provide economic and environmental benefits. IMTA is the practice which combines the cultivation of fed aquaculture species (e.g. finfish/shrimp) with organic extractive aquaculture species (e.g. shellfish/herbivorous fish) and inorganic extractive aquaculture species (e.g. Seaweed) to create balanced systems for environmental sustainability (bio mitigation) economic stability (product diversification and risk reduction) and social acceptability (better management practices). This system is entirely different from the ‘Polyculture’. In the Polyculture system fish share the same bio and chemical process which could eventually lead to shift in ecosystem. Another way to Define of IMTA is the farming of aquaculture species from different trophic levels and with complementary ecosystem functions, in a way that allows one species’ uneaten feed and wastes, nutrients and by-products to be recaptured and converted into fertilizer, feed and energy for the other crops, and to take advantage of synergistic interactions between species. IMTA is based on principle “The solution to nitrification is not dilution but extraction and conversion through diversification.” 

Criteria for selection of fish:

The following important criteria for selection of fish in IMTA system:

  Adaptation to tropical environment

  Acceptance to all types of feed like natural and artificial feed

  Amiability to live together

  Compatibility

  High Market demand

  High market prices 

Benefits:

  Effluent bio-mitigation: Mitigation of effluents through the use of bio-filters which are suited to the ecological niche of the aquaculture site. This can solve a number of the environmental challenges posed by monoculture aquaculture.

  Increased profits through diversification: Increased overall economic value of an operation from the commercial byproducts that are cultivated and sold. The complexity of any bio-filtration comes at a significant financial cost. To make environmentally friendly aquaculture competitive, it is necessary to raise its revenues. By exploiting the extractive capacities of co-cultured lower trophic level taxa, the farm can obtain added products that can outweigh the added costs involved in constructing and operating an IMTA farm. The waste nutrients are considered in integrated aquaculture not a burden but a resource, for the auxiliary culture of bio-filters.

  Improving local economy: Economic growth through employment (both direct and indirect) and product processing and distribution.

  Form of ‘natural’ crop insurance: Product diversification may offer financial protection and decrease economic risks when price fluctuations occur, or if one of the crops is lost to disease or inclement weather.

  Disease control: Prevention or reduction of disease among farmed fish can be provided by certain seaweeds due to their antibacterial activity against fish pathogenic bacteria.

  Increased profits through obtaining premium prices: Potential for differentiation of the IMTA products through eco-labelling or organic certification programmes. 

Challenges:

  Higher investment: Integrated farming in open sea requires a higher level of technological and engineering sophistication and up-front investment.

  Difficulty in coordination: If practised by means of different operators (e.g. independent fish farmers and mussel farmers) working in concert, it would require close collaboration and coordination of management and production activities.

  Increase requirement of farming area: While aquaculture has the potential to release pressure on fish resources and IMTA has specific potential benefits for the enterprises and the environment, fish farming competes with other users for the scarce coastal and marine habitats. Stakeholder conflicts are common and range from concerns about pollution and impacts on wild fish populations to site allocation and local priorities. The challenges for expanding IMTA practice are therefore significant although it can offer a mitigation opportunity to those areas where mariculture has a poor public image and competes for space with other activities.

  Difficulty in implementation without open water leasing policies: Few countries have national aquaculture plans or well developed integrated management of coastal zones. This means that decisions on site selection, licensing and regulation are often ad hoc and highly subject to political pressures and local priorities. Moreover, as congestion in the coastal zone increases, many mariculture sites are threatened by urban and industrial pollution and accidental damage. 

Status of IMTA in India:

IMTA is not popularized and commercialised in India. It is practiced on a research basis and in small scale only. In India, Mandapam region of Ramanathapuram district has got into the development of IMTA fisheries. Mandapam Regional Centre of CMFRI (Central Marine Fisheries Research Institute) which introduced Integrated Multi-Trophic Aquaculture (IMTA) to Munaikadu fishing group, engaged in commercial seaweed farming, has helped them harvest 652 kilograms of cobia fish and 2,700 kg of seaweed. The CMFRI had been developing technologies for seed production of high-value finfish and sea cage farming techniques and standardised seed production technologies of cobia and silver pompano. As the anticipated expansion of sea cage farming could lead to environmental degradation and cause diseases, the centre introduced IMTA to achieve biomitigation along with the increased biomass production by integrating different groups of commercially important species with varied feeding habits. The CMFRI introduced the concept to a fishermen group already practising commercial level seaweed farming and helped them with three numbers of low-cost cages, stocked with 100 cobia fingerlings each. The Centre also supplied 720 kg of seed material for seaweed integrating with the cages during the first week of April. A total of 12 numbers of seaweed rafts — 60 kg of seaweed per raft — were integrated with the cobia cages during the second week of September, he said. The daily feeding of the fishes with trash fishes, maintenance of the cages and the required watch were done entirely by the fishermen group. The success can be considered as the initial step towards development of a fullfledged integrated marine fish farm at Munaikadu, which will be the first of its kind in the country where seaweed, mussel/oyster, lobsters, high-value marine food fishes and ornamental fishes can be farmed.