Have you heard that the world is in a terrible state? An understatement = Our world’s coastal zones (within 200km of the shore) are predicted to house 75% of the population by 2016 (~ 6 billion people). These numbers are predictions, and they may be off, but the point remains…our planet, especially our coasts, requires attention to deal with increasing demands on the dwindling resources. Countries, especially coastal countries, will require comprehensive planning to mitigate the swarms of people that will need food, shelter, and jobs.

What can industry players do about that? “That’s not the question I would ask next” you say? Yet, it is the next question that matters. The majority of people involved in industry must care about planning for sustainability, or it is too late. When industry is on board with, then sustainability will be easier to achieve. How?

Integrated Multi-Trophic Aquaculture!

Not the full solution to the problems of the world, but it’s a great start.

Definition 1. Integrated multi-trophic aquaculture (IMTA) is an ecosystem based management approach that effectively mitigates the overabundance of nutrients introduced by fish farming. The lower trophic level organisms provide a biofiltration (filtering the water clean of small particles) service to cleanse the excess particulate matter (via shellfish) and nutrients (via seaweeds) from the environment and incorporate that material into their tissues (Folke et al. 1998, Neori et al. 2004, Whitmarsh et al. 2006). This method of aquaculture is capable of accomplishing the bioremediation of coastal waters (seaweeds and shellfish are used as biological nutrient removal systems), and economic diversification (production of other marine crops of commercial value within the same cultivation unit) (Thierry Chopin laboratory website).

Definition 2. Integrated multi-trophic aquaculture (IMTA) is a form of marine farming that utilizes the ecosystem services provided by organisms of low trophic levels (e.g. shellfish and seaweed) raised in appropriate ratios to mitigate the effects of organisms of high trophic levels (e.g. fish).

Whaooooooh horsey…Is there enough jargon in those definitions? First, I need to define ecosystem services and trophic levels. I’ll define trophic level first, that’s the easy one. The term comes right out of grade 11 biology – the trophic level of a plant or animal is the feeding position within the food web that it occupies. Plants are in the lowest or 1st trophic level (the most important level to life on planet earth), and animals that eat plants (herbivores) are at the next level, and animals that eat animals are in the highest trophic levels. The definition of ecosystem services requires a book, but a section of this teeny paper will have to do.

Ecosystem Services

The new term on the block is Ecosystem service. It is a phrase for which the definition is still being debated, and the concept is not intuitive. It may however, be the key to success for winning the business opinions over to the thinking that “sustainability is good”. A benefit to talking about ecosystem service is that this concept can entice economically motivated people to think about sustainability, because it can make or save huge sums of money. For example, the value or worth of a forest is worth more than simply it’s timber. How much is the forest worth? Ecosystem service valuation of forests includes many aspects that are not usually given a dollar value. The forest is valued for the flood prevention service, the erosion control, water filtration and flow regulation services of the roots and litter. The carbon absorption of the trees, shrubs, and herbs provide a reservoir to slow global warming. The forest creates oxygen. The forest is also home to pollinating species required by agriculture (bees) and florists (the birds and the bees). Recreation services are also abundantly utilized in forests.

This concept has resulted in seemingly unlikely people working hard to save large tracts of forests. For example, in New York City, officials were faced with the water supply being polluted and made a decision to save the Catskills watershed rather than sink billions of dollars into a water filtration plant (which would require a yearly budget and an eventual upgrade). The city literally saved billions of dollars. That tale would have been completely successful if they had only saved more of the watershed from development. Multi-national companies saved the forests surrounding the Panama Canal to ensure continued save passage by reducing erosion (clogs the canal) and to provide an even water flow (to ensure that the water required to operate the canal locks is present). The forests were saved to save money, billions of dollars.

IMTA and Ecosystem Services

So…what is the ecosystem service value of an oyster? What is the ecosystem service provided by seaweeds? Here’s a story to illustrate how ecosystem services work within IMTA:

Let’s pretend you are a salmon in with all the other salmon swimming around, depressed out of your tree (off topic … a trout researcher from Regina believe salmonids get depressed! This has further implications, but that’s another story). Fish flakes come pouring in, you and your cohort all jostle for a tasty bite. The current is sweeping through and your bite is swept from your reach and out of the net pen. You go for another bite. Your fishy belly will be full by the end of the feeding period, not to worry, there’s always too much food. The farmer wants to ensure that you and your siblings will be big and juicy for the market. This is the major point made earlier: Fish farmers introduce an excess quantity of particulate matter (uneaten food) into the water column by feeding their high trophic level fish stocks. In turn, these fish stocks excrete a surplus of nutrients, such as nitrates and phosphates.

Now let’s follow that fish flake. It’s free from the salmon gauntlet, but in IMTA, the second wave off attack is still ahead, oysters are growing close enough to the pens to absorb up that excess food material. Oysters are filter feeders, and they will ingest a large portion of the food that the fish do not, and incorporate that food into their tissues. Theoretically, the big juicy oysters will also be available for commercial harvest, and the farmers and markets will be happy.

The environment is not completely happy yet. All those excess nutrients (nitrogen and phosophorous) that the fish excrete and result in eutrification of the water column (excess nutrients result in algae blooms that smother everything else) need to be addressed. However, the farmer is also growing seaweed or kelp around the oysters. The seaweed is of the lowest trophic level, and the growth of those organisms is dependent on nitrogen and phosphorous. There’s a lot around, the seaweed flourish and can be sold on the open market. Again, the farmer is happy, the market is happy, and the environment is happier too.

Fish Farming in brief

The excessive amount of nutrients that fish farming introduces into the ocean has been one of the main reasons for the unsustainable nature of those business ventures. Management practices of fish farms leave much to be desired. Excess particulate matter and nutrients have been largely left unchecked, resulting in ecologically dead zones below the aquaculture nets and an increased occurrence of algal blooms. The unsustainable practices currently employed by most fish farmers resulting in degradation of the environment leading to the very poor social image of the industry may change if IMTA was put into general practice.

It’s time

Several pledges have been proposed to help solve the many global issues humans are faced with. In my opinion, IMTA (within a comprehensive, interdisciplinary coastal management framework) is the most promising resolution thus far, and industry plays a major role in the implementation.

It is industry that drives our economy and politicians listen to industry more than any other sector of society. When big business discovers common ground to agree with environmental organizations and municipalities on sustainability issues, saving the world will be a little easier.

Of course saving the world with IMTA is a slight exaggeration, however, it offers an economically attractive and ecologically sustainable alternative to conventional salmon farming.

Dr. Thierry Chopin (University of New Brunswick) has been leading the “Development of integrated aquaculture (fish/shellfish/seaweed) for environmentally and economically-balanced diversification and social acceptability” project since 2001.

This collaborative project, which includes natural and socio-economic scientists from the University of New Brunswick, industrial partners, and federal and provincial agencies (the Department of Fisheries and Oceans, the Canadian Food Inspection Agency, the Atlantic Canada Opportunities Agency and the New Brunswick Innovation Foundation), has been very successful due to the dedication of the team and their inter-disciplinary approach. The team also deliberately chose to be involved in the dissemination of knowledge through a very diversified array of media (peer reviewed papers, book chapters, workshops and proceedings, non-refereed technical papers, magazine and newspaper articles, DVDs) to reach out to researchers, federal and provincial agencies and regulators, industry, professional associations, environmental NGOs, First Nations, and the general and school public. (Aquaculture Today)

The current research is underway with the University of New Brunswick (Dr. Thierry Chopin), Department of Fisheries and Oceans (Dr. Shawn Robinson), and the Canadian Food Inspection Agency (CFIA) to understand IMTA and to develop standardized tests for food safety within this new management strategy. The regulation in the CFIA operation manual (28/01/2005) that prohibits this form of aquaculture states: Shellfish and finfish should not be raised in close proximity as net pens have the potential to be point-sources of pollution due to human activity and poor husbandry practices. There should be a minimum of a 125 m prohibited area surrounding net pens. The size of this area will be dependent on the size of the finfish site and on the hydrography surrounding the site (see Section b) ii)).

This legislation has remained unchanged despite over 5 years of research in Canada showing the benefits of IMTA. Fish farmers that wish to do business in a sustainable manner are unable to so to the fullest extent possible due to this prohibitive legislation. At least one major industry wants to save the world, but the government will not allow it …yet.


Aquaculture Today.

Canadian Food Inspection Agency. 28/01/2005. Canadian Shellfish Sanitation Program – Manual of Operations.

Chopin, Thierry. Seaweed and Integrated Multi-Trophic Aquaculture (IMTA) Research Laboratory.

Folke, C., Kautsky, N., Berg, H., Asa, J., and M. Troell. 1998. The ecological footprint concept for sustainable seafood production: A Review. Ecological Applications, 8(1) Supplement, S63-S71.

Neori, A., Chopin, T., Troell, M., Buschmann, A., Kraemer G., Halling C., Muki Shpigel, M., and C. Yarish. 2004. Integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modem mariculture. Aquaculture, 231 (1-4): 361-391.

Whitmarsh, DJ, Cook, EJ, and K.D. Black. 2006. Searching for sustainability in aquaculture: An investigation into the economic prospects for an integrated salmon-mussel production system. Marine Policy, 30 (3): 293-298.

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Penny spends half her time as a MSc student studying Porphyra in the Resource Mangement and Environmental Studies program and the other half studying Porphyra on Gabriola Island. Her continued involvement with First Nation fishery departments gives her a unique perspecitive on marine biology and how important business and policy are to functioning in the real world. Thus she returned to school to take courses and to finally get back into the field. She likes taking photos of seaweed, musicians, babies, fog/mist, and her dog.