November 2019 (13:2)

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Aquaculture production is an increasingly important component of global seafood production. Seafood production from aquaculture has expanded nearly six-fold since 1990, while capture fisheries production has remained relatively stagnant. According to the UN Food and Agricultural Organization’s most recent analysis of global fisheries and aquaculture, seafood production from aquaculture (excluding seaweeds) exceeded production from marine capture fisheries for the first time in 2016.[i]

Aquaculture’s reputation is mixed, however. It obviously has the potential to feed many people, but it has is associated with a number of observed and potential negative environmental impacts, including:

  • Altering and destroying habitat, such as mangrove forests, for aquaculture facilities
  • Escapes of farmed species into the wild, enabling species invasions and altering the genetics of wild populations
  • Spreading diseases and parasites to wild populations
  • Releasing fecal waste, uneaten food, and pesticides into the local environment, decreasing water quality
  • Contributing to the overfishing of wild fish populations because of the use of wild fish to feed farmed fish.

This negative view obscures the incredible diversity of aquaculture types and their diverse interactions with marine environments. Aquaculture enterprises vary in:

  • What species are cultivated (e.g., seaweeds, mollusks, crustaceans, finfish) and what they feed on (e.g., whether they are photosynthesizers, filter feeders, deposit feeders, herbivores, carnivores)
  • How intense production is (e.g., total biomass per cage, the degree to which fertilizer and supplementary feeds are used)
  • The type of environment production takes place in (e.g., freshwater streams or lakes, fully enclosed tanks, ponds, intertidal, sheltered bays, open ocean, sea pens, ponds, tanks).

Careful siting and management of aquaculture facilities can avoid many of the negative impacts listed above, and new research is calling attention to how many types of aquaculture (particularly that of primary producers and filter and deposit feeders) can provide conservation benefits (e.g., serving as de facto marine protected areas and alleviating wild harvest through replacement or supplementation) and a range of other ecosystem services (e.g., providing habitat, removing excess nutrients in the water column, attenuating wave energy, and sequestering and storing carbon).

In this issue we feature five areas where aquaculture’s interactions with marine ecosystems (and/or our understanding of them) are evolving. We interviewed experts about recent research and developments related to:

We also speak with a biotechnology researcher about the current status of “cellular aquaculture” – the cultivation of seafood tissue in a laboratory or factory environment rather than in an aquatic environment.


Rebecca Gentry: Marine aquaculture can remove nutrients

Editor’s note: Rebecca Gentry is a postdoctoral researcher in the Department of Geography at Florida State University. Her research focuses on spatial ecological and socioeconomic questions related to marine aquaculture development.

The Skimmer: In a recent paper, you reviewed research on a variety of ecosystem services that marine aquaculture can provide in addition to fulfilling its principal commercial objectives of providing food, pharmaceuticals, and other products. These additional ecosystem services include augmenting wild fisheries catches, sequestering carbon, regulating ocean acidification, protecting coastlines, removing nutrients from the water, improving water clarity, and providing artificial habitat. For which of these services is there the strongest evidence right now, and what types of aquaculture provide those services?

Gentry: In our research we found nutrient removal to be the most thoroughly documented ecosystem service provided by marine aquaculture (aside from directly producing food and other materials). This ecosystem service has been widely studied using a range of techniques, including laboratory studies, modeling exercises, and direct measurement of nutrient removal. Algae and bivalves (e.g., clams and mussels) are the most commonly studied species with regard to nutrient removal. But we found that there is evidence for nutrient removal for a range of other species, such as polychaetes and sea cucumbers. Although the potential for nutrient removal is promising, it is important to remember that many types of marine aquaculture (such as most types of finfish farming) add nutrients to the environment and that even some species that are noted for their nutrient removal ability (e.g., bivalves) can also release nutrients into the water column. Understanding that different species interact with the environment in a variety of ways can help inform marine aquaculture development that maximizes ecosystem service benefits and minimizes negative environmental impacts.

The Skimmer: If aquaculture can provide these other ecosystem services, it would be optimal for ocean planning to begin to incorporate consideration of them when siting aquaculture. Are there currently any examples of entities siting aquaculture in ways that maximize other ecosystem services?

Gentry: There are certainly places, such as Jamaica Bay in New York, that are using restorative aquaculture techniques (e.g., aquaculture methods used to promote ecosystem health) to harness the water quality, substrate stabilizing, and habitat provisioning services provided by shellfish. There is also continued interest in integrated multi-trophic aquaculture (IMTA), the co-locating of farms of different species together so that the wastes from one type of farming can be assimilated by other species (e.g., the culturing of finfish, mussels, and seaweed together). [Editor’s note: Read more about IMTA here.] There are IMTA farms in places ranging from Sanggou Bay, China, to pilot projects in the Bay of Fundy, Canada. Most marine spatial planning for marine aquaculture that I am aware of has focused on avoiding the negative effects of marine aquaculture development, but I think that future planning would benefit from integrating the ecosystem services from aquaculture into the process. One example of the types of analyses needed to do this include a 2014 project that mapped locations in the Maryland state waters of the Chesapeake Bay where shellfish aquaculture could contribute to water quality goals and coastal zone enhancement.

 

Hot off the presses: Global analysis of locations for restorative aquaculture

A paper published in October 2019 provides a global analysis of locations where shellfish and seaweed aquaculture have the greatest potential to restore coastal ecosystems and provide benefits to people. Researchers found the greatest opportunities for restorative shellfish aquaculture in Oceania, North America, and Asia, and the greatest opportunities for seaweed aquaculture distributed throughout Europe, Asia, Oceania, and North and South America. View the map.


Gesche Krause: Siting aquaculture offshore can reduce environmental impacts and stakeholder conflicts

Editor’s note: Gesche Krause is a social scientist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Researcher in Germany. Her research focuses on the social dimensions of marine resource use and social and economic dimensions of sustainable aquaculture.

The Skimmer: Can you tell us a little bit about the status of offshore aquaculture right now?

Krause: As the global population increases, the growing demand for seafood and stagnating supply from capture fisheries creates pressure on aquaculture to fill this gap. Aquaculture production has grown at an average rate of more than 6% annually over the past decade, and today, aquaculture supplies over half of the seafood consumed globally. Further expansion of aquaculture in nearshore environments is difficult, however. Coastal populations and maritime uses have soared in abundance and intensity over the past few decades, and there is tremendous competition for marine space. In Europe, this has created scope to research radical new ways of using marine space efficiently, such as the recently completed EU-funded Multi-Use in European Seas (MUSES) project.

As a result of this new thinking, offshore aquaculture is gaining prominence. Situating aquaculture farther offshore can reduce both the environmental impacts on and the environmental impacts from aquaculture (e.g., nutrient input from terrestrial systems and nutrient effluents from aquaculture) as well as reduce stakeholder conflicts. Moving aquaculture offshore may also enable the large-scale growth in the aquaculture sector necessary to enhance food security for a growing world population.

Several industrialized countries – including China, South Korea, and Norway – are rapidly developing futuristic open ocean finfish systems.[ii] For instance, in Norway, the government granted production licenses, known as “development licenses”, to companies that committed themselves to developing prototypes of installations for offshore salmon (Salmo salar) aquaculture. Once the prototypes are developed, the companies can convert the development licenses to ordinary production licenses. Two of these prototypes are now in operation. Although these prototypes are located within national waters, they are designed to withstand the forces of exposed locations farther offshore (see Figure 1).

In addition to salmon, other offshore farms grow yellowtail (Seriola rivoliana) in the open ocean off Kona, Hawaii, and Bahia de La Paz, Mexico, and seabream (Sparus aurata) off the coast of Ashdod, Israel, in the Mediterranean Sea. Commercial mussel farming currently exists in offshore waters in several countries – Ireland, Scotland, Germany, Belgium, the Netherlands, France, the US, Canada, Japan, China, and New Zealand. All of these farms are in waters with medium to high primary productivity that is favorable to growing mussels.

The Skimmer: What are the major benefits and challenges of offshore aquaculture versus more traditional coastal aquaculture, including benefits or challenges related to marine ecosystem health?

Krause: Moving offshore makes large tracts of relatively uncontested space available for aquaculture. From a production perspective, offshore aquaculture locations can be favorable because they often have higher flushing rates and an absence of parasites. These factors minimize opportunities for disease and parasite transmission and can enable faster growth rates of extractive species (e.g., mussels) and higher yields. This supports efficiency of production and reduces environmental impacts on other locations.

Offshore aquaculture also presents substantial challenges, however. Harsh, high energy offshore environments require new engineering concepts and new farming approaches to maximize the potential for sustainable production and give potential investors in the industry the confidence to invest. Offshore aquaculture also requires clear and secure legal frameworks to avoid “sea grabbing” and the unregulated urbanization of ocean space. Currently, in many countries there is no clear regulation of potential offshore cultivation candidates and/or the application process for starting an offshore aquaculture production enterprise is unclear and complicated. While nearshore aquaculture primarily creates scope for local jobs and incomes, offshore aquaculture in the globalized economy could create benefit for regions or nations other than the nations that hold the rights to the exclusive economic zones (EEZs) where operations are taking place. This holds the potential to shift power relations and create ambiguities about who benefits from use of the ocean commons.

Another consideration for offshore aquaculture is that it may be economically advantageous to design offshore aquaculture installations as multiple-purpose systems, especially when it comes to aquaculture planned in an integrated multi-trophic aquaculture (IMTA) framework. [Editor’s note: Read more about IMTA here.] This will allow aquaculture to capitalize on new as well as existing offshore infrastructure (e.g., wind farms, decommissioned offshore oil platforms) and save on construction and operation costs. However, the integrated farming of vastly different organisms with different needs in an IMTA system is complex at best.

It is also important to note that less than 40% of aquaculture today is of an intensive nature. As crops increase in value, however, lower-intensity systems are likely to be updated and could be converted to IMTA systems. The Green Aquaculture Intensification (GAIN) project in Europe is currently conducting research on circular economy approaches to aquaculture and how it can be intensified in an ecologically sustainable manner.


Thierry Chopin: Integrated multi-trophic aquaculture (IMTA): an ecosystem-based approach to aquaculture

Editor’s note: Thierry Chopin is a professor of marine biology and director of the Seaweed and Integrated Multi-Trophic Aquaculture Research Laboratory at the University of New Brunswick in Canada. He is also president of Chopin Coastal Health Solutions Inc. His research focuses on the ecophysiology/biochemistry/cultivation of seaweeds and the development of IMTA for environmental sustainability, economic stability, and societal acceptability.

[The responses below are excerpted from a longer interview with Thierry Chopin. Read the full interview.]

The Skimmer: Can you tell us a little bit about what IMTA is?

Chopin: With IMTA, farmers cultivate species from different trophic levels and with complementary ecosystem functions in proximity. They combine fed species (e.g., finfish that need to be provided with feed) with extractive species (e.g., seaweeds, aquatic plants, shellfish, and other invertebrates that extract their food from the environment) to take advantage of synergistic interactions among them. In these systems, biomitigation operates as part of a circular economy (i.e., nutrients are no longer considered wastes or by-products of one species, but instead are co-products for the other species).

The scope of the IMTA concept is extremely broad and flexible and is always evolving. IMTA can be applied worldwide to open-water and land-based systems, marine and freshwater systems, and temperate and tropical systems. Consequently, it can’t be reduced to a short bureaucratic definition indicating species, type of infrastructures, number of infrastructures, distances, etc. Its versatility is remarkable.

The Skimmer: Can you tell us more about the benefits of doing IMTA?

Chopin: Seaweeds are excellent nutrient scrubbers – especially of dissolved nitrogen, phosphorus, and carbon. IMTA takes advantage of the benefits of nutrients, which in moderation (i.e., within the assimilative capacity of the ecosystem) are co-products and food, not waste or by-products.

Nutrient biomitigation is also not the only ecosystem service provided by seaweeds, and IMTA is more than a story of nutrients. For example:

  • Seaweed cultivation does not require arable soil or the transformation of land (e.g., deforestation with its attendant loss of ecosystem services) for agriculture.
  • It may be stating the obvious, but seaweed aquaculture does not require irrigation as access to water of appropriate quality becomes more and more an issue.
  • Seaweed cultivation does not require the addition of fertilizers and agrochemicals like in terrestrial agriculture, especially in an IMTA setting where the fed aquaculture component provides nutrients.
  • If appropriately designed, seaweed cultivation provides new habitats and can help restore ecosystem functions.
  • While all other components (fed finfish and invertebrates) are oxygen consumers, seaweeds are photosynthetic organisms that produce oxygen and help to avoid coastal hypoxia.
  • By sequestering carbon dioxide dissolved in seawater, seaweeds could also play a significant role in increasing pH in seawater, thereby reducing coastal acidification.
  • While performing photosynthesis, seaweeds also absorb carbon dioxide and sequester carbon, even if in a transitory manner. Consequently, they could slow down global warming, especially if their cultivation is increased and becomes more widespread globally.
  • Seaweeds can be a substitute for fish protein in aquaculture feed, thus reducing the carbon footprint of fed seafood aquaculture.
  • Increasing the production of sustainable, safe, equitable, resilient, and low-carbon sources of food from the ocean (e.g., invertebrates, seaweeds, and finfish) could mitigate food insecurity and reduce emissions from land-based food production (e.g., red meat).
  • The IMTA multi-crop diversification approach (e.g., raising finfish, seaweeds, and invertebrates together) could mitigate and manage economic risk from climate change and coastal acidification impacts.
  • IMTA systems could be associated with wind farms in integrated food and renewable energy parks (IFREP) to reduce the cumulative footprint of these activities.

[These responses are excerpted from a longer interview with Thierry Chopin. Read the full interview.]


Stefano Longo: Aquaculture not a “relief valve” for fishing pressure on wild stocks

Editor’s note: Stefano B. Longo is an environmental sociologist in the Department of Sociology and Anthropology at North Carolina State University. His research examines the relationships between social and ecological systems, with an emphasis on marine ecosystems, political economy, and the globalization of food systems.

The Skimmer: Many people see marine aquaculture as a way to reduce overfishing on wild finfish and invertebrate stocks. You recently looked at whether this is actually occurring. Can you tell us about how you looked at this and what you found?

Longo: There are many pressures on wild finfish and invertebrate stocks from fishing to other human impacts such as climate change and habitat loss. Aquaculture is often presented as a sort of “relief valve” for capture fisheries and a solution to the problems associated with overfishing. Our recent study examined whether aquaculture production does indeed displace fisheries capture (i.e., substitute farmed seafood for wild seafood). We used World Bank and FAO data and multiple models to assess this relationship (i.e., whether and how much aquaculture has displaced fisheries capture) over time within nations around the world. We did not find convincing evidence that global aquaculture production to date has displaced or suppressed fisheries capture.

The Skimmer: So what are some possible reasons why aquaculture isn’t reducing fishing pressure on wild stocks (and may even be increasing pressure on some stocks)?

Longo: There are likely several social explanations for why aquaculture production has not significantly suppressed fisheries capture as expected. Global factors such as economic growth influence seafood production and demand and have likely contributed to overall increases in fisheries production and consumption. Promoting production and consumption of farmed seafood may also stimulate demand for all types of aquatic-based foods, including wild finfish and invertebrates. And many intensive aquaculture operations need fish-based sources of feed such as fishmeal and fish oil that are provided by capture fisheries.

The Skimmer: Do you think there is ever the potential for aquaculture to reduce fishing pressure on wild seafood stocks? What would need to change/be different?

Longo: There is certainly great potential for aquaculture to reduce pressure on wild stocks, but our study suggests that this is not as straightforward as it might seem. Aquaculture is part of a bigger social picture. And the seemingly logical notion that the production of one farmed fish will replace one wild fish does not hold because social factors such as economic development, trade, and commodity production – influence production and consumption. The goals of many aquaculture production systems may not be to displace fisheries capture. Larger transformations in socioecological relationships, especially in the socioeconomic system, are necessary if aquaculture is to help reduce pressure on wild stocks.

 

“To move things in the right direction, production of seafood in aquaculture (and fisheries) could benefit from producing species lower in the food web, such as mollusks… More importantly, socially prioritizing producing food (and in this case seafood protein) as a basic right to meet needs, rather than as simply another commodity in the global economy, and regulating production in an ecologically sound manner, would advance conservation goals while meeting human needs. This would require strong political-economic initiatives (policies) on national and global levels that better plan production, and implement, and enforce regulations that promote sustainability.”

------ Stefano Longo, North Carolina State University


David Little: Use of fish meal and oil in aquadiets is declining, and innovative substitutes are emerging

Editor’s note: David Little is a professor of aquatic resource development with the Aquaculture Systems Research Group at the Institute of Aquaculture of the University of Stirling in the United Kingdom. He specializes in aquatic resource development and capacity building with a focus on Asia.

The Skimmer: Can you tell us a little about the use of fish products derived from wild fish (e.g., fish meal, fish oil) to feed farmed marine species? How much impact does the extraction of wild fish to feed farmed species seem to have on marine ecosystems?

Little: Wild fisheries have been a cornerstone for supporting human diets, probably since we evolved as modern humans, and their exploitation continues to be a critical part of the human food basket. Human interventions into natural ecosystems (both terrestrial and aquatic) to access food have always had impacts; but the demands of industrial urbanized societies in the last two hundred years have greatly accelerated these impacts and in some cases led to losses of biodiversity and ecosystem functionality. Fish that are caught may be used either directly for human food or indirectly as an ingredient in livestock – including fish – diets. Typically, fish used in livestock diets were lower value, often small-sized species. Nowadays fish from feed-fisheries and the byproducts from fish processing are converted into “marine ingredients” e.g., fish meal and fish oil – to feed livestock. Waste material from the processing of wild and farmed fish (e.g., fish heads, viscera, skin) makes up an increasing share – now believed to be more than one third – of the raw material converted to marine ingredients. The extent to which aquaculture is a driver for the fishing of feed fish is up for debate, but this issue is continuously reinforced by media interest in salmon and shrimp that have been dependent on marine ingredients in feed.

When thinking about the impact of the use of marine ingredients on marine ecosystems, it is important to keep several points in mind:

  • Most farming of finfish and other aquatic species actually occurs away from coastlines in freshwater ponds and involves herbivorous and omnivorous species that do not require marine ingredients in their diets (although they may be fed marine ingredients depending on the cost-benefit analysis). There has been rapid growth of marine carnivorous species in recent decades – often in cages located in coastal waters – but this is a relatively small part of the global farmed crop.
     
  • As the farming of marine carnivorous species was getting started, fish were fed moist diets of fresh, ground-up, low-value fish that were by-products of fisheries. This caused all sorts of problems. The unprocessed “feed” fish were highly perishable under tropical conditions and often led to nutritional diseases in the farmed fish. Use of moist diets has also been implicated in pathogen transfer, local pollution, and poor performance of the system as a whole. The shift to formulated diets in which fishmeal and fish oil are just partial ingredients has been a transformative step in the growth of farmed commodity species such as Atlantic salmon and catfish.
     
  • Two trends in the use of marine ingredients have emerged in recent decades. First, the volume of marine ingredients used to feed fish has grown (as a proportion of the total available) while the volume used to feed other livestock has declined. Second, the inclusion rate of fishmeal and oils in aquadiets has declined rapidly. International certification of both fisheries and the aquaculture sector as well as basic economies have driven both of these trends.

The Skimmer: What are the major alternatives to using fish meal and fish oil to feed farmed carnivorous species, and what are some of the pros and cons of moving to these alternative food sources?

Little: As the use of marine ingredients in aquadiets has declined, it has largely been replaced by conventional alternative ingredients also used for terrestrial livestock, e.g., soy-based products to replace fishmeal and terrestrial-derived oils to replace fish oils. Many of these alternative ingredients have their own sustainability issues. Soy production has been responsible for rainforest destruction in South America, palm oil has been responsible for loss of forest habitat and human rights abuses in Southeast Asia, and even rapeseed oil is associated with the loss of pollinating insects in Europe. In addition, these alternative ingredients are associated with other problems. Farmed marine fish fed high levels of terrestrial ingredients do not perform as well (e.g., have lower survival rates and/or poorer individual growth) and can have welfare problems (e.g., morphological/physiological abnormalities and/or reduced resistance to disease). In addition a reduction in marine lipids in the diets fed to farmed fish leads to a reduction in their level of “good fats”, particularly the highly unsaturated fatty acids only available from marine food chains such as DHA and EPA.

The cost of marine ingredients from wild fisheries has steadily increased over the past decades due to their high value and limited volume. These cost increases have stimulated a raft of innovative substitutes that are just now beginning to be used in diet formulations at scale. For example, high protein and lipid products based on various microorganisms are now moving from pilot to production scale. These include:

  • FeedKind, a product developed decades ago using bacteria that use methane as a nutrient source
  • Veramaris, a product based on a microalgae product rich in omega-3 fatty acids
  • Multiple products based on fungi that use low value or waste products (e.g., from the forestry sector) as substrates.

Production of high omega-3 fatty acids from transgenic terrestrial oil crops (e.g., Camelina) has also been demonstrated and, should their inclusion become accepted, this would be the most cost effective approach to the mass production of marine quality lipids.

 

Cellular aquaculture: Seafood without the sea?

Editor’s note: Natalie Rubio is a PhD candidate and New Harvest Research Fellow in Biomedical Engineering at Tufts University. Her research focuses on cellular agriculture. She published a paper “Cell-Based Fish: A Novel Approach to Seafood Production and an Opportunity for Cellular Agriculture” in Frontiers in Sustainable Food Systems earlier this year. In this paper, she suggests that cell-based seafood could promote marine conservation by providing an alternative source of marine animal-based protein (possibly reducing the need for fishing and/or conventional aquaculture). She also discusses how fish cells may be more suitable to being grown in laboratories and mass production than mammal and bird tissues because some fish are adapted to low oxygen and low temperature conditions.

The Skimmer: Can you tell us about what cellular aquaculture is?

Rubio: Instead of catching or farming whole fish to harvest their muscle and fat tissues for fillets, fish sticks, and sushi, we can grow fish muscle and fat stem cells outside of the fish itself. This new approach, called cultured fish/seafood or cellular aquaculture, involves just growing the parts that we want in our food and not the eyes, skin, or bones.

The Skimmer: How far along are we in making cellular aquaculture a reality?

Rubio: There’s still a lot of work to be done before cultured fish products are available to the public. Right now, researchers can generate small amounts of tissue for large amounts of money. To create viable products, companies need to scale up production and greatly reduce manufacturing costs. The first products will likely look like processed fish products (e.g., surimi and fish paste). Products with more structure (e.g., fillets and sushi) are further away.

The Skimmer: What sorts of finfish or shellfish would this work for?

Rubio: In theory, this process can be applied to any type of fish or other animal because all animals have stem cells. It is easier to grow cells from animals that are well researched because we know more about their cell biology. Salmon muscle cells have already been cultured, for example.

The Skimmer: What sort of inputs would be needed, including from the marine environment?

Rubio: A (simplified) cellular aquaculture process involves selecting a target species, isolating cells from that species, expanding the cells in a bioreactor with nutrient-rich growth media, and maturing the cells into structural tissues. So, donor fish are needed for initial cell isolations, growth media (which does not need to come from the marine environment) is required to feed the cells, and bioreactor systems are needed to cultivate the tissues. It's also possible to use an edible material (i.e., scaffold) to grow the cells on – this provides extra surface area for growth and could add to the texture, taste, and nutrition of the final product. Some scaffold materials that researchers have been experimenting with include alginate, cellulose, and chitosan.

Editor’s note: You can read more about cellular aquaculture here and here.

 


[i]According to the UN Food and Agricultural Organization, in 2016, production from aquaculture was 80 million tons – 29 million tons from marine aquaculture and 51 million tons from inland aquaculture. Production from capture fisheries was 91 million tons – 79 million tons from marine capture fisheries and 12 million tons from inland capture fisheries.

[ii] It is also important to note that although we use the term “offshore” in this interview, offshore suggests a given distance (e.g., nautical miles) from the shoreline. In many cases, however, exposed conditions can be found within a few kilometers of shore. In these cases, the terms “aquaculture in high energy environments” and “exposed aquaculture” help express the design and production challenges that these nearshore and offshore industries share.

And if you’re interested in some more reading, another recent news article that caught our attention was:

Editor’s note: Thierry Chopin is a professor of marine biology and director of the Seaweed and Integrated Multi-Trophic Aquaculture Research Laboratory at the University of New Brunswick in Canada. He is also president of Chopin Coastal Health Solutions Inc. His research focuses on the ecophysiology/biochemistry/cultivation of seaweeds and the development of Integrated Multi-Trophic Aquaculture (IMTA) for environmental sustainability, economic stability, and societal acceptability.

The Skimmer: Can you tell us a little bit about what IMTA is?

Chopin: With IMTA, farmers cultivate species from different trophic levels and with complementary ecosystem functions in proximity. They combine fed species (e.g., finfish that need to be provided with feed) with extractive species (e.g., seaweeds, aquatic plants, shellfish, and other invertebrates that extract their food from the environment) to take advantage of synergistic interactions among them. In these systems, biomitigation operates as part of a circular economy (i.e., nutrients are no longer considered wastes or by-products of one species, but instead are co-products for the other species).

The scope of the IMTA concept is extremely broad and flexible and is always evolving. IMTA can be applied worldwide to open-water and land-based systems, marine and freshwater systems, and temperate and tropical systems. Consequently, it can’t be reduced to a short bureaucratic definition indicating species, type of infrastructures, number of infrastructures, distances, etc. Its versatility is remarkable.

IMTA’s ultimate aim is to ecologically engineer a whole new era of aquaculture systems that:

  • Increases environmental sustainability by providing nutrient biomitigation and other ecosystem services and using green technologies
  • Promotes economic stability by improving output, lowering costs, diversifying product, reducing risk, and creating jobs in coastal and rural communities
  • Increases societal acceptability of aquaculture by improving management practices and regulatory governance, implementing nutrient trading credit incentives, and providing differentiated and safe products.

The Skimmer: Can you describe how widespread IMTA is and what an IMTA setup might look like?

Chopin: Asian countries such as China have a long IMTA tradition (although their systems are not always described using this acronym), and IMTA operations cover vast dedicated areas.

On the other hand, western world research groups working on IMTA have spent the past 2-3 decades developing small-scale, mostly pre-commercial, IMTA operations by modifying relatively small finfish sites to co-cultivate invertebrates and seaweeds.[i] Commercial scaling-up has been difficult because while the biological and environmental advantages of IMTA are generally accepted, there are significant economic and regulatory adoption barriers.

In Canada, we got started with the cultivation of salmon, kelps, and blue mussels within existing finfish aquaculture sites because this enabled us to conduct experiments at sea (as opposed to in the laboratory in small tanks) within the limitations of the regulatory system that was in place. But IMTA was never conceived to be just this setup, and it must be stressed that there is no one IMTA system to feed the world. Different climatic, environmental, biological, physical, chemical, economic, historical, societal, political, and governance conditions prevail in different parts of the world and will lead to different designs for the best suited IMTA systems.[ii]

The Skimmer: Can you tell us more about the benefits of doing IMTA?

Chopin: Seaweeds are excellent nutrient scrubbers – especially of dissolved nitrogen, phosphorus, and carbon. IMTA takes advantage of the benefits of nutrients, which in moderation (i.e., within the assimilative capacity of the ecosystem) are co-products and food, not waste or by-products.

One way to incentivize mono-aquaculturists to move towards IMTA would be to allocate a value to the ecosystem services that seaweeds and other extractive species provide in addition to their biomass and food trading values. Much has been said about carbon sequestration and the development of carbon trading taxes. In coastal environments, mechanisms for recovering nitrogen and phosphorus should also be highlighted and accounted for in the form of nutrient trading credits (NTCs). Seaweeds are approximately 0.35% nitrogen (N), 0.04% phosphorus (P), and 3% carbon (C). If NTCs are valued at US$10-30/kg, US$4/kg, and US$25/ton for N, P, and C respectively, worldwide seaweed aquaculture (30.1 million metric tons) provides ecosystem services valued between US$1.1 to 3.2 billion. This is as much as 28% of their present commercial value (US$11.7 billion).

The value of this important service to the environment, and consequently society, is never accounted for in the budget sheets or business plans of seaweed farms and companies, however.[iii] Recognizing and implementing NTCs would give a fair price to seaweeds and other extractive aquaculture species.

Nutrient biomitigation is also not the only ecosystem service provided by seaweeds, and IMTA is more than a story of nutrients. For example:

  • Seaweed cultivation does not require arable soil or the transformation of land (e.g., deforestation with its attendant loss of ecosystem services) for agriculture.
  • It may be stating the obvious, but seaweed aquaculture does not require irrigation as access to water of appropriate quality becomes more and more an issue.
  • Seaweed cultivation does not require the addition of fertilizers and agrochemicals like terrestrial agriculture does, especially in an IMTA setting where the fed aquaculture component provides nutrients.
  • If appropriately designed, seaweed cultivation provides new habitats and can help restore ecosystem functions.
  • While all other components (fed finfish and invertebrates) are oxygen consumers, seaweeds are photosynthetic organisms that produce oxygen and help to avoid coastal hypoxia.
  • By sequestering carbon dioxide dissolved in seawater, seaweeds could also play a significant role in increasing pH in seawater, thereby reducing coastal acidification.
  • While performing photosynthesis, seaweeds also absorb carbon dioxide and sequester carbon, even if in a transitory manner. Consequently, they could slow down global warming, especially if their cultivation is increased and becomes more widespread globally.
  • Seaweeds can be a substitute for fish protein in aquaculture feed, thus reducing the carbon footprint of fed seafood aquaculture.
  • Increasing the production of sustainable, safe, equitable, resilient, and low-carbon sources of food from the ocean (e.g., invertebrates, seaweeds, and finfish) could mitigate food insecurity and reduce emissions from land-based food production (e.g., red meat).
  • The IMTA multi-crop diversification approach (e.g., raising finfish, seaweeds, and invertebrates together) could mitigate and manage economic risk from climate change and coastal acidification impacts.
  • IMTA systems could be associated with wind farms in integrated food and renewable energy parks (IFREP) to reduce the cumulative footprint of these activities.

In the recently published UN report “The Ocean as a Solution to Climate Change: Five Opportunities for Action” we show that seaweed farming could remove an additional 0.3 GtCO2e/year by 2050, for a total mitigation potential of 1.4 GtCO2e/year from the conservation, restoration, and sustainable management of coastal and marine “blue carbon” ecosystems such as mangroves, seagrasses, salt marshes, wild seaweed beds, and reefs. The report estimated that five ocean-based climate actions could deliver a fifth of the annual greenhouse gas (GHG) emissions cuts needed by 2050 to keep global temperature rises below 1.5°C.

Furthermore, with regard to economics, we recently published a paper that demonstrated that an IMTA operation is more profitable than salmon monoculture with a higher net present value (NPV) in all the scenarios tested. In addition, in regions where salmon production has declined in recent years, such as in Atlantic Canada, the crop diversification associated with IMTA could increase economic stability.

The Skimmer: In addition to nutrient trading credits, what else needs to be done to further develop and expand IMTA?

Chopin: Despite our recent findings about the profitability of IMTA versus salmon monoculture as well as other recent studies demonstrating the positive financial results of IMTA systems, the adoption of IMTA at a commercial scale in Canada and other western countries is relatively slow. Why? For starters, it always takes time for the knowledge acquired in academic studies to be transferred to industry, investors, and regulators. Economic studies of IMTA only span the past decade. Other barriers to the adoption of IMTA at present include:

  • Uncertainty related to IMTA’s financial and environmental performance
  • The present short-term linear management approach of aquaculture companies (versus a long-term circular approach)
  • IMTA’s increased operational complexity
  • Non-conducive policy and regulatory frameworks (at provincial and federal levels).

For IMTA to expand dramatically in the western world, we need a number of things to happen. First and foremost, we need a major rethinking regarding the functioning of an “aquaculture farm”. We need to stop thinking about an aquaculture farm as something that operates within the limits of a few buoys arbitrarily placed in the water by humans or a few GPS coordinates on a map. While western IMTA has generally developed within the restrictive limits of existing finfish sites, this does not reflect the ecosystem scales at which aquaculture farms really function.

In addition, the mentality that nutrients are wastes or by-products rather than co-products useful for the co-cultivation of other crops needs to change. Different nutrients (i.e., small particulate organic nutrients, large particulate organic nutrients, dissolved inorganic nutrients) need to be recaptured, and different spatial and temporal strategies need be designed to do this. The “integrated” in IMTA should be understood as cultivation in proximity in terms of connectivity in ecosystem functionality, not absolute distance. This means that the different components of an IMTA system do not necessarily have to be at the exact same location (e.g., within relatively small finfish sites). Rather entire bays/coastal areas/regions (including marine protected areas) could be the units of IMTA management within an Integrated Coastal Area Management (ICAM) strategy, thereby challenging traditional aquaculture regulations/policies.[iv]

“Multi-trophic” refers to the incorporation of species from different trophic or nutritional levels in the same system. It is not enough to consider multiple species (like in polyculture) – they have to be at multi­ple trophic levels based on their complementa­ry functions in the ecosystem. Species selection, combinations, and proportions will be highly variable depending on the local conditions and biodiversity. The co-cultured species should be more than just biofilters; they should also be harvestable crops of economic value or potential. Moreover, nothing says that only one company should be in charge, producing all the IMTA components. There may need to be several companies coordinating activities within an ICAM.

Just like fisheries regulations, regulations governing aquaculture are often designed with a single species/group of species in mind and can inhibit a more holistic approach by not considering species interactions and an ecosystem-based management approach. Dialogue between scientists, aquaculturists, regulators, and other coastal stakeholders will be key to addressing regulatory hurdles and establishing enabling regulations and conducive societal conditions for the development and implementation of innovative practices such as IMTA.

IMTA: An ancient practice in Asia and very new in the western world

From “Integrated Multi-Trophic Aquaculture: Ancient, Adaptable Concept Focuses On Ecological Integration” by Thierry Chopin:

“IMTA can be traced back to the origins of aquaculture. In 2200-2100 B.C., the document You Hou Bin detailed the integration of fish with aquatic plants and vegetable production in China. There is evidence of Nile tilapia grown in integrated agriculture-aquaculture drainable ponds on bas-reliefs in tombs built during the era of the New Kingdom in Egypt, which occurred about 1550-1070 B.C.

"Between 500 and 1848 A.D. Ahupua'a integrated agriculture-aquaculture freshwater-to-marine farming systems were developed in Hawai'i.

“During the French Renaissance (~ 1600 A.D.), royal IMTA was practiced at the Château de Fontainebleau, as attested by the construction of the Etang aux Carpes (Carp Pond), which still functions to this day. French King Henri IV had given instructions that the estate should be self-sufficient and could not depend on provisions, which had the chance of being looted several times during the 65-km trip from Paris.

“In 1639, Nong Zheng Quan Shu (The Complete Book on Agriculture) by Xu Guangqi was published posthumously. He had been collaborating with Jesuit missionaries. His comprehensive treatise covered many topics, including irrigation and the rotation of fish and aquatic plant production. Also described were the integration of fish with livestock and the effects of manure on pond production, as well as the integrated production of mulberry trees, rice paddies and fish ponds.

“In the 1970s, John Ryther reignited interest in IMTA and can be considered the grandfather of modern IMTA for his seminal work on what he called “integrated waste-recycling marine polyculture systems,” first at Woods Hole Oceanographic Institution in Massachusetts, USA, and then at Harbor Branch Oceanographic Institute in Florida, USA.”

“It was followed by three productive decades on what has been variously called polyculture, integrated mariculture or aquaculture, ecologically engineered aquaculture and ecological aquaculture. Understanding the need to harmonize all these names, the author and Jack Taylor combined integrated aquaculture and multi-trophic aquaculture into the term integrated multi-trophic aquaculture in 2004.”

And in our recent interview, Dr. Chopin related a little more about this most recent development in the western world.

“In September 1995, I gave a presentation entitled “Mixed, integrated, poly-, or multi-level aquaculture - whatever you call it, it is time to put seaweeds around your cages!” at a conference in St. Andrews, New Brunswick, Canada. I could see a number of faces in the room saying, “What is this guy talking about?”!

“The period 1995-2000 was spent “preaching in the desert” for what was termed “integrated aquaculture”. We wanted to differentiate our practice from monoculture, and the obvious term was polyculture. However, cultivating three species of fish together constitutes polyculture but does not address the problems of co-cultivating three fed species together.

“In March 2004, at a workshop in Saint John, New Brunswick, we gave another name to what we were doing. I came up with “integrated aquaculture”, and Jack Taylor with “multi-trophic aquaculture”. We combined the two, and “Integrated Multi-Trophic Aquaculture” or “IMTA” was born. In the 15 years since, more than 1,300 publications referencing IMTA have been published worldwide.”

For a timeline of IMTA development in both Asia and the West, see here.

 

[i] Modern fish aquaculture developed in the 1970-80s, and invertebrate and seaweed aquacultures were added in the 2000s.

[ii] As with the music of J.S. Bach, there are many variations on the IMTA theme, including: integrated agriculture aquaculture (IAA), integrated fisheries aquaculture (IFA), integrated silviculture (mangrove) aquaculture (ISiA), integrated green water aquaculture (IGWA), integrated biofloc aquaculture (IBFA), integrated temporal aquaculture (ITA), integrated sequential aquaculture [ISA, also called partitioned aquaculture (PA) or fractionated aquaculture (FA)], sustainable/sustained ecological aquaculture (SEA), aquaponics or freshwater IMTA (FIMTA), integrated peri-urban aquaculture (IPUA), integrated ocean ranching (IOR), and integrated food and renewable energy parks (IFREP).

[iii] I would also note that the above calculations are based on costs of recovering nitrogen and phosphorus in wastewater treatment facilities and values often cited for carbon tax schemes. It is interesting to note that the value for carbon is per ton, whereas those for nitrogen and phosphorus are per kilogram. This suggests that there is more money to be made with NTC (between US$1.1-3.2 billion for N and US$48.2 million for P) than with CTC (only US$22.6 million for C).

By Tundi Agardy, Contributing Editor, The Skimmer. Email: tundiagardy [at] earthlink.net

A recent publication “Marine zoning revisiting: How decades of zoning the Great Barrier Reef has evolved an effective spatial planning approach for marine ecosystem-based management” published in Aquatic Conservation: Marine and Freshwater Ecosystems distills important lessons from Australia’s evolving commitment to manage the world’s most iconic multiple use marine protected area. It casts a critical eye on what has worked and what has not, and it pushes us beyond our marine comfort zone to face the challenge of true ecosystem-based management (EBM), which neither ocean zoning nor marine spatial planning (MSP) in their current applications can adequately provide. With this publication, Jon Day and his coauthors have given the world a valuable gift that will keep on giving if we can acknowledge this gift and heed it.

Day and his colleagues (including Richard Kenchington, who like Day has been intimately involved in the design and management of the Great Barrier Reef Marine Park [GBRMP] through its various iterations over the years) recount how zoning both set the stage for multiple use management and evolved to provide the legal framework for regulations to protect the world’s largest barrier reef. The use of zoning had to be adapted over decades because the GBRMP Authority was a pioneer in spatial management and the allocation of space to uses of the marine environment. Zoning on land may have provided a glimpse of the possible, but adapting zoning approaches to the fluid and obscured ocean realm required experimentation and a fair amount of risk taking.

Zoning lessons learned from the GBRMP

Some critical lessons from Day et al. (2019) include:

  • Lesson 6: Although the International Union for Conservation of Nature advocates protecting at least 30% of marine waters in highly protected area, this does not mean every MPA needs to aim to protect this percentage from the time of initial designation.
  • Lesson 8: Role of political engagement. Zoning cannot occur in a ‘political vacuum’; zoning is primarily a political process that needs to consider the interests of all stakeholders and be in keeping with the political aspirations of the government(s).
  • Lesson 9: Prerequisites for effective zoning include high‐levels of political buy‐in enhanced by ongoing public participation.
  • Lesson 10: Public engagement. All zoning processes should include genuine and effective public engagement; this requirement will generally preclude a relatively quick or inexpensive zoning process.
  • Lesson 11: Adjacent areas. Zoning needs to consider, and wherever possible complement, adjacent coastal and marine areas. This includes the need to consider other key marine-related policies.
  • Lesson 12: Ecological connectivity is an important concept when determining zoning.
  • Lesson 13: Wherever possible, zoning decisions should consider all the values (ecological, social, cultural and economic) within, and surrounding, an MPA.
  • Lesson 14: Complementary zoning across adjoining jurisdictions. Such zoning can provide many advantages, by enhancing public understanding as to what is allowed, or not allowed, across broad areas of the marine environment.
  • Lesson 15: Zone by objective, not activity. Zones should not be based around individual activities; rather, the key determinant should be activities that are compatible with the zone objectives.

Read more about these and other lessons learned.

Some of the lessons learned

In total, Day and his colleagues offer 38 lessons from the four decades that the GBRMP Authority applied zoning as the foundation for multiple use management on the reef and its associated ecosystems.  Some of the most interesting include Lessons 6, 8-10, 13, and 15:

  • Lesson 6 reminds me of the line from Pirates of the Caribbean that describes the pirate’s code as “more of a guideline than a rule.”
  • Lessons 8-10 stress the importance of social and political engagement – systematic conservation planners and ivory tower academics beware!
  • Lesson 13 on considering all the values a place provides is critically important and could be a paper in its own right.
  • However, for me, the most valuable lesson is captured in Lesson 15: zone by objective, not by activity. This gets to the fundamental importance of setting objectives for zoning for MPAs and marine management more generally. Performance-based zoning can yield positive results, but only if it is tailored to the problem that management is meant to address.

Zoning can be so much more, though

I do have a slight bone to pick with Day and his co-authors, however, regarding their reluctance to give zoning its due. That seems a strange thing to say since the entire paper illustrates the ability of the zoning approach, especially as it evolved in the GBRMP, to be efficient and effective. But Day and others are quick to point out that zoning provides only one layer of MSP and is not the be all and end all of integrated management. I take a broader view. In my mind zoning is more than a tool or an information layer that leads to a legal framework for allocating use – it is a mindset. Zoning forces us to take stock of what we know, acknowledge what is most ecologically important to protect for sustainable use, and recognize connections between ecosystem components (including those on land and in freshwater) and between human use and ecosystem function. Good zoning is likely the only way to preserve these connections and maintain ecosystem function, and it can guide the use of all the other management tools that must also be used – such security and surveillance regimes, use of permits, innovative financing for marine management, and on and on. I’m not saying zoning is a panacea – but it is a solid footing to allow us to grab complex marine management issues by the horns.

In fact, zoning as an approach (as opposed to zoning as a legal tool) can go beyond MSP. Day and coauthors pay homage to this in Lesson 11 on considering adjacent areas, Lesson 12 on connections, and Lesson 14 on complimentary areas – but they could have gone further to chart a course correction that is needed in MSP right now. MSP seems, by unfortunate accident of its own evolution, constrained to the purely marine environment. But taking stock of what we know about ecosystems to plan EBM allows us to identify places not only in the sea (water column and benthos) but also places on the coast that need special management to keep systems healthy and productive. Marine management authorities may not have jurisdiction over land area, but they can identify important ‘zones’ on land and along water bodies that need special attention and engage the appropriate authorities in land and water management to lessen negative impacts on marine ecosystems. Although a bit too late, this is what GBRMP Authority did when it engaged with the State of Queensland to work on the run-off affecting water quality on the Great Barrier Reef. I recognize this is a very loose interpretation of what is meant by zoning – but it is the logical extension of an approach that takes what we know, puts it on a map, and uses it to steer management in an EBM direction.

I would say this paper offers one more lesson – perhaps the most important of all: unless we cast a critical eye on how management is implemented and what it achieves, no amount of theoretical modelling, MPA design, or MSP processes will result in the positive outcomes we need. The lessons that Day and his colleagues offer are grounded in pragmatism – and should be paid heed. Campaigns to stop eating fish, ban bottom trawling globally, use nature-based solutions to tackling climate change, and the like are all well and good to engage the public, but when it comes to the paramount but difficult issue of what use to allow where, only real experience can guide us. And given the prospects that Australia and the Great Barrier Reef are facing today, maybe there is a 40th lesson in there, too – it’s now or never to pay attention and apply the lessons learned in marine ecosystems everywhere.