//Aquaculture 55
FEEDING BOTH POND AND FISH: A PATHWAY 
TO ECOLOGICAL INTENSIFICATION OF 
AQUACULTURE SYSTEMS
By Olivier Joffre and Marc Verdegem
The nutritious pond concept is a novel approach that enables the pond itself to contribute significantly 
to the diet of the farmed fish/shrimp. Our research shows that feeding the pond by balancing the 
carbon-to-nitrogen ratio can increase the contribution of naturally occurring food in the diets of the 
cultured animals, thus enhancing reliance and reducing production costs and environmental impact. 
Field trials are currently being conducted in Vietnam and Bangladesh to better understand nutrient 
transfer in aquaculture ponds. The results of these trials will inform the development of products for 
fish farmers that have high potential for scaling to other developing countries. 
increase feed supply while mitigating environmental impact. 
Research on the impact of aquaculture on surface water 
quality and greenhouse gas emissions shows that aquaculture 
is lagging behind livestock and agriculture (Zhang et al. 2015). 
This is despite significant improvements in recent decades 
in aquaculture system efficiency through, for example, the 
reduction and replacement of fish meal and fish oil in diets. 
At present, however, feeding systems target the cultured 
animals with little attention paid to the possible contribution 
of the pond ecosystem and its food web to the animals’ diet.
What is a nutritious pond?
 Credit: Olivier Joffre In a typical aquaculture production system, the food web (i.e. 
Shrimp farmer applying carbohydrate to stimulate microbial activity in the the food chain within the pond, from phytoplankton, microbes 
pond, in turn enhancing mineralisation of wastes and other organisms through to the fish or shrimp cultured 
in the pond) is stimulated by uneaten and undigested feed, 
Introduction which essentially acts as an expensive fertiliser in the pond.
Aquaculture is one of the fastest growing food production This fertiliser is not designed to be efficient for the pond 
sectors in the world and now provides more than 50% of the ecosystem, as its nutritional composition is aimed at fish 
fish and shellfish consumed globally. This growth is predicted or shellfish and not the other pond organisms. This creates 
to continue in the coming years. However, the sector is highly imbalances in the system and in the nutrient cycles. The 
dependent on agricultural crops and wild fish for feed as well recycling of animal waste becomes suboptimal, making the 
as freshwater and land resources for inland aquaculture. pond environment unhealthy and vulnerable to disease. 
At the same time, scientists and policy analysts have raised In general, farmers around the world, and especially in 
concerns about the environmental impact of such growth developing countries, use a variety of probiotics, prebiotics 
and the need to steer the sector toward more resilient and and other additives to mitigate these imbalances, increasing 
sustainable production. the production cost without necessarily achieving the desired 
outcomes.
As aquaculture has expanded and intensified, so has its 
dependence on natural resources. Future growth will depend One solution is a system that feeds both the pond and the 
on the sector’s ability to overcome this dependence, and cultured animals, limiting imbalances in the nutrient cycles 
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56 Aquaculture//
by producing wastes that are easily decomposed. As a result, The project is developing the concept using shrimp (P. 
mineralisation is fast, the production of natural foods for the vannamei) in Vietnam and genetically improved farmed 
animals is optimal, waste accumulation is minimised and the tilapia (GIFT) in Bangladesh aquaculture systems as a model, 
pond environment stays clean and healthy. This is the idea and an innovation platform to design the technology in 
behind the nutritious pond concept, which aims to harness order to facilitate its uptake by the sector. Hence, the project 
the potential of a largely untapped resource: increasing involves industry (Nutreco in the Netherlands, Skretting and 
the harvest of pond nutrients via the food web and turning Viet Uc in Vietnam), universities and research organisations 
waste into food for the animals. It is an approach that could, (Wageningen University & Research in the Netherlands, Can 
in theory, be scaled to a large number of semi-intensive Tho University in Vietnam and WorldFish, an international 
production systems as it is estimated that more than 60% non-profit research organisation based in Malaysia) as well 
of all finfish and shrimp comes from these systems. Such an as Vietnamese and Bangladeshi farmers. Additional external 
approach would support the intensification of aquaculture stakeholders from the Vietnamese aquaculture sector 
while minimising environmental impacts. (international NGOs, certification bodies, extension officers 
and private sector actors) are also members of the innovation 
The microbial food web is influenced by modifying the dietary platform and provide feedback during the design process.
macronutrient composition of the feed, e.g. crude protein, 
fat, starch and non-starch polysaccharides. If nutrients Fundamental and applied research conducted by PhD 
are immobilised in the food web, fewer accumulate in the students in Wageningen is shared with members of the 
sediment, reducing the denitrification process and increasing innovation platform to inform the design of on-farm trials in 
the loss of valuable nitrogen. At present, nutritious pond feeds P. vannamei semi-intensive systems. The fundamental 
mainly focus on raising the carbon-to-nitrogen (C:N) ratio in research investigates the natural production of essential fatty 
the pond in order to maintain fast recycling of the waste. An acids (a crucial but expensive component of fish feed) by algae 
advantage is that carbon-rich ingredients are cheaper than in the pond, and the utilisation of this natural food source 
nitrogen-rich ingredients, thus reducing feed costs. by the shrimp. Another area of research is the quantification 
of different paths for nutrient transfer in the pond. We are 
investigating the direct contribution of formulated feed 
to animal growth and the importance of the natural food 
produced by the pond itself and how this contribution 
changes with different C:N ratios. Findings from this research 
ultimately aim to improve feed formulation by valorising the 
contribution of natural foods to shrimp production in semi-
intensive ponds.
Finally, a PhD student based at Can Tho University is looking at 
 Credit: Olivier Joffre the interactions of algae and bacteria to find ways to balance 
Checking shrimp (P. vannamei) growth in a nutritious pond system their ratio for optimal biological processes in the aquaculture 
environment. The research is also testing the response of the 
Research on feed and nutrient cycles in ponds is limited. There pond to different types of carbohydrate, the application form 
is also limited knowledge on how fish growth relies on feed and application frequency.
directly and how it is influenced indirectly by the stimulation 
of natural food production. Our research is helping to fill that 
knowledge gap.
How are we developing the concept 
into a product?
The nutritious pond project is a five-year research initiative 
funded by the Netherlands Organization for Scientific Research 
(NWO) and the WorldFish-led CGIAR Research Program 
on Fish Agri-Food Systems. It involves a multi-stakeholder 
 Credit: Olivier Joffre
approach to embed fundamental and applied research along 
with product design to adapt the new feeding system to the Members of the innovation platform are made up of farmers, researchers, 
local technological, social and institutional context. NGOs, extension officers and private sector actors
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//Aquaculture 57
This array of research, which is providing deep insight into shrimp diet and a concept diet that did not contain any fish 
pond ecology and nutrient transfer, is shared with and oil or fish meal. An analysis of the weight of organic matter 
discussed by different stakeholders involved in the innovation (grams) at the start and end of the experiment in the different 
platform to design new protocols for on-farm trials. Platform components of the pond’s food web indicated that the 
members defined their requirements and expected nutrient transfer was not efficient. 
performance to evaluate the trials. Since the beginning of 
the project in 2016, four different formulations combining 
pelleted feed and different types of carbohydrate (molasses, 
cornstarch, a mix of rice bran and cassava, or cassava on its 
own) have been tested in semi-intensive shrimp ponds in 
Vietnam. In Bangladesh, on-farm testing was performed on 
GIFT, and the nutritious pond feed was designed as a single 
pellet with a higher carbohydrate content. 
 Credit: Devi Hermsen
Simulated rearing mesocosm tanks at Wageningen University & Research 
(WUR), allowing a full nutrient budget to be made considering the cultured 
animals, water column, sediment and periphyton
The experiment showed that only a small 18% of organic 
matter ends up as shrimp organic matter, and the rest ends 
up in the food web. The experiment also showed that shrimp 
fed a diet without fish meal and fish oil sourced at least 31.5% 
and 6.2% of their total EPA-gain and DHA-gain (two major 
types of omega-3 fatty acids) respectively from the algal-
based food web. This tells us that, if well managed, a pond’s 
primary production can significantly contribute to the 
shrimps’ requirement for highly unsaturated fatty acids, 
indicating that feed formulation could be optimised for this 
(expensive) dietary component.
The results also showed that lowering the dietary protein-
to-energy (P:E) ratio below the known optimal ratio does 
not affect fish productivity. The concept diet contained only 
24% protein and 3% fish meal. In conventional feeds, this 
 Credit: Kazi Kabir is typically between 30-35% protein and 10-15% fish meal. 
These results were tested in semi-intensive tilapia ponds 
Farmers in Bangladesh check tilapia grown in household ponds using a 
nutritious, high C:N ratio feed in Bangladesh (Kabir et al. 2018). Using a low-protein diet, 
the yield was 21% higher compared to the conventional 
Results and evidence for a new diet. Analysis of the nutrient transfer in the pond showed 
feeding system that 64% of the growth recorded was achieved from natural 
food produced by the pond. The analysis also showed that it 
Research in a controlled environment (mesocosm tanks) is possible to manage more than 85% of nitrogen retention 
provided key insights on pond ecology and nutrient transfer. in a pond by optimising the P:E ratio of the pond and diet 
For example, we tested two types of feed: a conventional (Figure 1). 
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58 Aquaculture//
Figure 1: Nitrogen gain in fish fed a control diet or a high The way forward
C:N diet
In a recent study using life cycle assessment to compare the 
environmental impact of different aquaculture production 
systems, Henriksson et al. (2018) noted that producing 
more fish using less feed would result in some of the largest 
improvements in the environmental performance of most 
aquaculture systems.
The nutritious pond project has provided evidence that 
feeding the pond as well as the animal can produce more 
animal protein with less feed. Now entering its final phases, 
the project expects to translate its findings into new 
commercial products such as low-protein feed and culture 
protocols. 
Nitrogen gain in fish fed a control diet or a nutritious, high C:N diet shows 
19% higher retention with the latter (Kabir et al. 2019) This type of feeding regime has high potential for scaling in 
developing countries, where aquaculture systems are not 
Manipulating the C:N ratio required some empirical tests on P. intensive and the cost of inputs hinders transition toward 
vannamei semi-intensive systems. Our research showed that more intensive systems using pelleted feed. We believe that 
a feed load reduction of 20% combined with a C:N ratio of this new type of feed management can contribute to the 
12, yielded a similar final shrimp weight as in control ponds ecological intensification of aquaculture systems, particularly 
where 100% of the feed load was applied. These results in Africa, where low-cost (but high-quality) feed is required to 
directly informed the design of experimental field trials in support the intensification and overall growth of the sector.
Vietnam. Some innovation platform members questioned the 
type of carbohydrate used. Tests in a controlled environment References
showed that cornstarch yielded significantly higher shrimp 
production, survival rate, growth rate and a better feed Henriksson, P.J.G., Belton, B., Mrushed-e-Jahan, K., Rico, A. 
conversion ratio (FCR) than cassava powder. These findings 2018. Measuring the potential for sustainable intensification 
were incorporated in the field trial design. of aquaculture in Bangladesh using life cycle assessment. 
Proceedings of the National Academy of Sciences, 
The results of the trials, conducted annually in a limited p.201716530. Available at: http://www.pnas.org/lookup/
number of ponds (three) and control ponds in the Mekong doi/10.1073/pnas.1716530115.
Delta, confirmed the tests in controlled conditions. In on-
farm conditions, we were able to raise productivity, lower Kabir, K.A., Schrama, J.W., Verreth, J.A.J., Phillips, M.J., 
input costs and increase financial returns from the pond by Verdegem M. C.J. 2019. Effect of dietary protein to energy ratio 
reducing the feed load by 10–20% while maintaining a C:N on performance of Nile tilapia and food web enhancement 
ratio of 12 by adding an external source of carbohydrate. in semi-intensive pond aquaculture. Aquaculture, 499 
(September 2018), pp.235–242. Available at: https://doi.
The nutritious ponds also displayed a more stable environment org/10.1016/j.aquaculture.2018.09.038.
than the control ponds, allowing a longer growth period and 
minimising early disease symptoms. This, in turn, reduced Zhang, Y, Bleeker, A ., Liu, L. 2015. Nutrient discharge from 
the use of probiotics and other additives, resulting in average China’s aquaculture industry and associated environmental 
financial savings of 10–15%. impacts. Environ. Res. Lett. 10 (2015) 045002. 
Dr Olivier Joffre is a Scientist working under the Dr Marc Verdegem is Associate Professor at the Aquaculture and 
Sustainable Aquaculture component of the WorldFish- Fisheries Group of the Department of Animal Sciences at Wageningen 
led CGIAR Research Program on Fish Agri-Food Systems. University in the Netherlands, where he has been engaged in 
His research focus is on technology design and farmer aquaculture research and development programmes since 1988. His 
behaviour to better understand innovation processes in research focuses on pond ecology and knowledge-based solutions to 
aquaculture. Prior to his engagement with WorldFish, improve feed utilisation efficiency in pond aquaculture, benefiting 
Olivier was international consultant in aquaculture and natural farm income and reducing the environmental impact from pond farming. Currently 
resources management in the Mekong Region. he is leading the development of the Nutritious Pond farming system through 
various partnerships with universities, the private sector and WorldFish. 
This article is a short summary of research outputs conducted by the authors and three PhD students: Devi Hermsen, Kabir Kazi and Tran Huu Tinh. This work 
was undertaken as part of the CGIAR Research Program on Fish Agri-Food Systems (FISH) led by WorldFish. The program is supported by contributors to the 
CGIAR Trust Fund. Funding support for this work was also provided by the Netherlands Organization for Scientific Research (WOTRO) and Science for Global 
Development (NWO-WOTRO).
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