FEATURE ARTICLE – Improving the public image of aquaculture

The latest piece in our series of expert contributions looks at integrated multi-trophic aquaculture and bringing awareness of the activity to the public.
Published: 4 November 2016

​​​​​​​​​​Laura Guimarães, C. Marisa Almeida, Isabel Azevedo, and Isabel Sousa Pinto, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Portugal

Despite its ancient roots, aquaculture remained mostly quiescent until the mid-twentieth century. Improved knowledge on the life-cycle of aquatic species, and the advent of reliable instrumentation to measure water parameters (e.g. dissolved O2 and CO2, pH, salinity, toxic ammonia, and nitrates) vital for aquatic organisms, allowing better control of culture conditions, triggered its development. After a slow start, aquaculture production has been expanding at a rapid steady pace since the 1980s.  

Better production efficiency and environmental sustainability

The rapid growth was, at a certain point, accompanied by the spread of major disease outbreaks among fish farms worldwide. This led to the wide use of antibiotics and other chemicals to treat these diseases, presenting a danger to human health. Other main aspects contributing to rising negative, often exaggerated, criticism of aquaculture are the wasteful use of water, the use of wild fish as meal to grow aquaculture species, and the environmental impact caused by polluted effluents that often leads to eutrophication and sedimentation of particulate organic residues.  

In the last decades, however, much effort has been made to improve aquaculture practices, and technological innovations have been put forward to improve efficiency of resource use and reduce the environmental impact of aquaculture. Among these are restrictions to the use of chemotherapeutic agents by several countries, strong innovation in feeds to decrease the use of fish meals, development of selective breeding for genetic improvement of cultured species, investigation and use of probiotics to improve growth, potentiate the immune system, and enhance disease resistance.  

Investment is also focused on devising nature-based solutions, meeting the need for water saving and reuse. Remarkable examples are the association of constructed wetlands to aquaculture effluents and the implementation of integrated multi-trophic aquaculture (IMTA). These systems allow for water re-circulation, fitting actual needs to close the loop within the water circular economy. Constructed wetlands envisage the reduction of bacterial and chemical inputs from aquaculture allowing for wastewater recycling and reuse. IMTA systems, in particular, involve the optimization of resource use through the combined culture of species from different trophic levels. 

Over the years, CIIMAR has been doing research into all these aquaculture aspects, including​ into IMTA to improve ecological and economic sustainability of this important activity. In fact, capture fisheries production is now known to have reached its sustainable limit over two decades ago, with many stocks already overfished. Aquaculture is thus essential to meet future needs of the growing human population for healthy protein from aquatic species as fish, shellfish and algae. 

Integrated multi-trophic aquaculture

IMTA consists of the integrated aquaculture of species occupying different positions in the food chain. In this concept, the waste products of one species are used as resources by another. Effluents of fish or shrimp aquaculture are rich in organic matter derived from feces and uneaten food, as well as excreted inorganic nutrients, mainly nitrogen and phosphorus compounds. In IMTA systems, aquaculture of species requiring external feeding is combined with organic (feeding on organic particles) and inorganic (removing dissolved nutrients from the water) extractive species. 

Common organisms used for organic extraction are suspension and deposit feeders. The former feed on small particulate organic matter, such as mussels, oysters and clams. Deposit feeders feed on larger particulate matter and may be sea cucumbers, sea urchins or polychaetes. Seaweeds (e.g. Ulva, Gracilaria, and Saccharina) are the typical inorganic extractive component of IMTA systems. The seaweeds produced can be used in a number of ways: human food, animal feeds, food and feed additives, fertilizers and plant improvement products, and phycocolloid extraction. More recently, they have also been used in the cosmetic, pharmaceutical, and biomedical industries due to their bioactive compounds. 

The use of state-of-the-art IMTA systems with species that are efficient biofilters and, at the same time, have high commercial value, is linked to waste reduction, but also to product diversification and social acceptability, increasing both environmental and economic sustainability of aquaculture. Whilst IMTA has already been studied for some years, it is only now reaching industrial aquaculture practice. The public in general is, thus, still unfamiliar with the IMTA concept and its advantages over conventional methods. Here, there is an opportunity to increase ocean literacy and create a positive image of sustainable aquaculture by showing how such systems as IMTA can reduce or eliminate some of the environmental problems while keeping economic and social benefits. Spreading basic scientific information on aquaculture and its different forms, and increasing discussion of existing and future options will favour responsible decision about aquaculture practices and will decrease suspicion regarding aquaculture products, especially those from IMTA sustainable productio


An effort in ocean literacy 

In Europe several projects are on course at local and regional levels with the ultimate aim of engaging citizens with the ocean. Sea Change is set to establish a fundamental change in the way European citizens view their relationship with the sea by empowering them to take direct and sustainable action towards healthy oceans and seas. Among other things, it is improving ocean literacy and assisting the EU Blue Growth strategy by increasing the European marine knowledge base about public understanding of how the seas behave and opening perspectives for career development in environmentally friendly marine industries, including aquaculture.  

Within the AORA-CSA project, tasked with supporting the implementation of the Galway Statement, cooperation between the aquaculture and ocean literacy working groups is facilitating mapping and connectivity of Atlantic research and outreach resources within these priority areas. School students are also becoming involved in ocean literacy. For instance, at a national level, OceanLab (supported by the EEA Grants) is bringing students into the lab to involve them in hands-on experiments that increase their perception of the ocean and its importance.  

IMTA exhibition module and student kit

To increase knowledge and tackle public apprehension over aquaculture impacts, an IMTA exhibition module and a hands-on experimental kit were developed by CIIMAR in the scope of OceanLab and Sea Change projects. The exhibition module was idealized to present the IMTA concept in a visually attractive setup, allowing discussion of its underlying nature-based mechanisms and advantages with general audiences and school students. The module was later transposed into a do-it-yourself kit, allowing middle to high-school students to build a small demonstration prototype of an IMTA installation in their science activity sessions.  

The kit employs a minimal amount of material easy to find in fish pet shops, i.e. small aquaria, air and water pumps, taps and silicone tubes, fish, filter or deposit feeders, seaweeds and simple-to-use ammonia, nutrients and pH test kits. Assembling is efficient and supported by a hypothesis-driven experimental protocol encompassing quantification of water parameters, graphical interpretation, and reporting and discussion of results. At present, the kit is in use by school students in northern Portugal. Likewise, CIIMAR is using it in dissemination to school teachers and marine educators. It can also be easily employed in public science centres, museums, and aquariums through training sessions and workshops .

Public acceptance and awareness

The IMTA module has been exhibited in international science, technology and business events, as well as national scientific festivals and science open days. The module is eliciting the curiosity of audiences with very different backgrounds and of varying levels of aquaculture knowledge. People are keen to receive details and understand the concept and usually take the opportunity to discuss their concerns about aquaculture products. They are learning more about biodiversity and ecosystem functioning and services, as well as the importance of aquaculture to the human population.  

The students' kit has been very well received by both the pupils and their educators. Its hands-on nature provides deep insight on system's structure and stability. It promotes comprehension of key aspects of efficiency in resource use and relevant ecological concepts, such as fish stocks or eutrophication, among others.  

Overall, these tools are fostering public understanding of the value of aquaculture and IMTA, reinforcing existing international efforts to advance acceptance and awareness about the sustainable exploitation of marine resources.


Laura was a speaker and participant at the recent EMSEA workshop in Belfast, co-sponsored by H2020 Sea Change and AORA-CSA, the latter of which ICES is a member.

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​​Photo: ​Andrea Warwick, Marine Scotland

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FEATURE ARTICLE – Improving the public image of aquaculture

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