Posted on February, 10 2017

Dr Mark Powell, seafood consultant for WWF with Dr Geoffrey Muldoon, Business and Industry Senior Manager, Coral Triangle Coordination Team

Picture this: a pastoral scene with a pond surrounded by mulberry bushes. Several species of fish grow in the water, mulberry leaves feed silkworms in a nearby shed, and each crop fertilizes the others. Is this fancy eco-agriculture run by scientists? No, it’s traditional low footprint fish and silkworm farming in Huzhou, west of Shanghai.    

Lowering the footprint of seafood¹ will help protect ocean ecosystems while meeting humanity’s growing demand for seafood. Is it possible to eat more seafood while reducing our impact on the ocean? Yes, and low footprint aquaculture can help. Why worry? Because our current seafood crop is taking a significant proportion of the ocean productivity that’s available. The downside risk of this goes beyond overfishing of a single species. If we overfish ocean productivity, we can’t just switch to another species for tomorrow’s fishing.  

Farming low footprint species makes sense, and there are many options. Low trophic level² fish like carp, milkfish, or tilapia can be grown with little or no fish products in feed, and bivalves (e.g. clams and mussels) can be grown without added food because they filter water to eat, with the added benefit that they improve water quality by removing nutrients. Low footprint aquaculture of these low trophic level species is not just wishful thinking, it’s happening today on a large scale.   

Most of the world’s aquaculture is farming of low trophic level species³. In 2014, global production of low trophic level carp species was >23 million tons per year, much higher than that of highly-traded “cash crop” species like shrimp and prawns (5.1 million tons), and salmon (2.3 million tons). Overall, low trophic level species made up 75 per cent of global aquaculture in 2006, albeit that these are predominantly farmed in Asia for local consumption and represent the traditional seafood diet of these countries.

Low trophic level aquaculture typically produces inexpensive food for domestic markets, so it doesn’t get a lot of attention in global media. Low trophic level species (herbivores and near-herbivores) can be grown with lower resource inputs compared to farming top predators like salmon and hence have a lower ecological footprint.  

When fed, low trophic level species require lower levels of fish products in feed thus making low footprint aquaculture far more efficient than the world’s fisheries at converting oceanic primary production into protein for people. Most of the world’s fisheries feed the world with high trophic level carnivorous fish species that require ten times (or more) the ocean primary productivity per kg of fish. Such inefficiency may not be an affordable luxury in the future, as demand for seafood increases.  

China produces more than three times the production of Indonesia, the world’s second-leading seafood producer. Most of China’s phenomenal growth in recent decades has been low footprint aquaculture.

China still has the most efficient seafood production⁴ in the world, and leads the world in seafood production, by a large margin; as much as ten times higher than European seafood production, which focuses on farmed and wild-caught predators. If China’s production of low footprint aquaculture were to convert to farming of Atlantic salmon or other predatory species, there simply would not be enough fish meal and fish oil in the world to provide the necessary feed to grow these fish.  

This worrisome thought experiment is not a total fantasy. With rising income and modernization, China’s aquaculture is indeed shifting towards farming of higher-trophic level predatory species. Growth of low footprint aquaculture has been about 6 per cent per year for the last 20 years, while aquaculture of predatory species has been about 17 per cent each year. This trend helps explain China’s increasing consumption of fish meal for aquaculture.  

In the interests of sustainable development, future aquaculture should be emphasizing the benefits of these low footprint species for which the technology is well-developed. The challenge however arises in terms of consumer demands and preferred diets. It is all well and good to say we need consumers eating more low-footprint species, but dietary preferences will not necessarily allow for this to happen. People cannot be forced to eat low-footprint species like carp and tilapia where these species have not been a historical part of their seafood diet.

Their cultural and behavioural aspects of seafood consumption represent a considerable  hurdle to overcome.
Another option for sustainable development is focusing research on methods to minimize the need for fish products in the feed of farmed predatory species. Promising options exist, such as farming insects to feed to fish, or producing the essential nutrients found in fish products through other sources such as algae.
 
Awareness of seafood footprint and the benefits of low footprint aquaculture can inform planning and investment and help ensure the long-term sustainability of food production by aquaculture and help support the future health of ocean ecosystems.  With growing demand for seafood, we can’t afford to ignore seafood footprint if we want to have both food security and healthy oceans.
 

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¹ Seafood includes products grown in freshwater and saltwater.  
² Low trophic level fish such as herbivores eat plants, while high trophic level fish (predators like salmon) eat fish or other animals.  
³ Responsible aquaculture and trophic level implications to global fish supply.  Tacon, A. G. J., M. Metian, G. M. Turchini, and S. S. De Silva, 2010.  Reviews in Fishery Science, 18: 94-105.
⁴ As measured by the primary production required, according to the methods of Pauly and Christensen, 1995.