Technologies for
Sustainable Aquaculture Development
Plenary Lecture II

Patrick Sorgeloos1

Laboratory of Aquaculture and Artemia Reference Centre
Ghent University, Belgium

Sorgeloos, P. 2001. Technologies for sustainable aquaculture development, Plenary Lecture II. In R.P. Subasinghe, P. Bueno, M.J. Phillips, C. Hough, S.E. McGladdery & J.R. Arthur, eds. Aquaculture in the Third Millennium. Technical Proceedings of the Conference on Aquaculture in the Third Millennium, Bangkok, Thailand, 20-25 February 2000. pp. 23-28. NACA, Bangkok and FAO, Rome.


Twenty-four years after the Food and Agriculture Organization of the United Nations (FAO) Technical Conference on Aquaculture in Kyoto, Japan, where my Asian experience started, I am particularly happy to present this lecture dealing with Research Priorities for Sustainable Aquaculture Development, a talk which is based on the keynote lecture I presented last year in Sydney at the World Aquaculture ‘99 Conference.

I would like to repeat my appreciation to many colleagues and friends from all over the world (in fact, many of them are attending this conference). Thanks for all the ideas and suggestions you provided me.

I would like to make a critical remark at the start of this presentation. Many reports propose that in the decades to come aquaculture should bridge the gap between market demand for aquatic products and supply from capture fisheries. I want to underline that there is great consensus in the research community that, following present-day aquaculture approaches, this is a very simplistic goal. It would not be the right decision to try to achieve this goal by applying current technology and business methods. Risks of major environmental and human-health problems need to be weighed against achieving a more cautious rise in production that is, in the longer term, sustainable. We should all see this not only as a challenge to do it well and responsibly, but also as a commercial opportunity for the industry.

Aquaculture is clearly at a crossroads and can come, in fact, should come of age in the twenty-first century. However, this will require more responsible researchers and more integrated R&D approaches than we apply at present.

  Allow me to simplify things by classifying present-day aquaculture into two types: traditional food aquaculture, mainly practised in Asia with a few species of freshwater and brackishwater fish, shellfish and sea weeds, and the more recent business aquaculture of shrimp, catfish and salmon, just to list the key groups. Although food aquaculture still represents the dominant output, this type of aquaculture has evolved along minimal research inputs. Trial and error practices, developed over several decades, even centuries, have resulted in well-balanced, extensive production systems. Continuous expansion of production area and further improvements in culture systems have been responsible for the fast growth over the last decades. Many agree, however, that productions cannot increase at the same pace, simply because of limitations of suitable water resources. Furthermore, the recent interest to “modernize”, which in fact means to intensify freshwater fish production, will imply very serious threats to sustainability.

Fast progress in business aquaculture has benefited most from R&D inputs, especially in western countries, although we need to admit that it has often been following very empirical approaches. Short-term oriented research had to find ways:

  • to grow the animal;
  • to maximize profitability; and
  • to assure long-term sustainability.

This three-step process has been accelerated by high profits, and accompanied by abuses in some regions (although at the start, often by ignorance) and vocal opposition to these types of industrial farming in some sectors of the nongovernmental organization (NGO) community. Still, in other wording, the approach has been to develop monocultures, and apply intensification, which brought about diseases.




Their treatments often resulted in more problems (e.g. bacterial resistance, not to speak of the environmental problems), until one realised that disease prevention is the new procedure to adopt.

It is interesting to see how both types of aquaculture begin duplicating some of each other’s approaches: business aquaculture starts to adopt the principle of polyculture widely applied in food aquaculture, whereas China is intensifying its traditional freshwater pond cultures and is using formulated feeds. Such approaches open very interesting opportunities, but serious constraints as well.

Further development of the aquaculture industry must take a holistic approach to culturing technologies, socio-economics, natural resour-ces and the environment, so that sustainability can be achieved. The momentum of the sustainability dialogue in aquaculture has increased dramatically in recent years.

Despite increasing institutional focus, the amorphous nature of the sustainability concept continues to constrain progress towards objective definitions and applications. It is here that researchers need to fill in by developing criteria and documenting test cases. At present, “codes of conduct” and “development criteria” often lead to over-generalizations and to qualitative goals with little or no specific means of measure or application.

One of these new concepts which deserves further study and application is the “ecological footprint”, which reflects the land and water areas necessary to sustain current levels of resource consumption and waste discharge by a given aquaculture practice. Cultures that combine species from different trophic levels, both terrestrial and aquatic, application of ecocyclic production, and generation of multiple services and outputs all can reduce the ecological footprint substantially.

All agree that freshwater resources are limited and, thus, priority is to increase production in the presently available volumes of water, not necessarily by further intensification but rather by polyculture and integration with terrestrial productions.

With regard to the coastal and marine environment, one has come to realize that these ecosystems must be managed as a whole, and that we need to model these systems for the nutrient carrying capacities of the different water systems involved, and for the various human activities and the different ecological conditions at any one location.


Various funding agencies are finally giving high research priority to “integrated coastal zone management studies”, which are not restricted to ecosystem studies involving biologists, oceanographers and aquaculturists, but consider the socio-economical and legal aspects as well. Our Asian colleagues, for example, have identified the need for more socio-economic studies for integrated farming systems in poor coastal communities, for example, by developing sustainable coastal production systems that integrate aquaculture and fisheries under community management. Conclusions from the research results of these studies in developing, as well as developed countries, may well be straightforward. However, it is clear that special motivation will be required to see proper implementation of the true cost of certain farming practices. New tax systems or - better even - a system of incentives should be considered here.

In the case of aquaculture activities in the coastal zone, the purpose is to reach a balance between “extractive” aquaculture and “fed” aquaculture. Extractive aquaculture refers to seaweed and mollusc farming, which can play a significant role in nutrient recycling, in fact of any waste nitrogen and phosphorus, not only from aquaculture farms. R&D projects in Europe are exploring the potential of extensive mariculture for “anthropogenic nutrient recycling”. Seaweeds are efficient nutrient scrubbers that could assist in the management of nitrification of coastal waters. Other ideas are based on the fact that the cost of mussel farming, if used only for nitrogen removal, is about the same as in a conventional purification plant.

Fed aquaculture systems are, for example, the cage farming of carnivorous marine fish such as salmon, bream and grouper. These systems might have to be removed from the more sensitive inshore waters to more offshore systems, eventually integrated with further nutrient trapping by seaweeds and molluscs. Shrimp farming is another example of such “fed” aquaculture systems, the impact of which on coastal ecosystems needs to be better remedied by integration with proper nutrient trapping and/or recirculation.

The next level to explore in the research priorities is the farmed species. There is general consensus that species diversification, especially of carnivorous types, is not a research priority.




Broad species diversification leads to an exponential growth of research requirements that are difficult to meet in view of limited resources. Clear exception is made for a few key species such as the genus Anguilla and the bluefin tuna, for which controlled breeding would mean a major breakthrough. In the case of eel, it would alleviate the pressure on wild stocks of glass eel in Asia as well as in Europe. Hatchery availability of bluefin tuna would reduce pressure on tuna fisheries and thus reduce the by-catch problem significantly. Still, little effort is devoted to search for, and to cultivate more species of shellfish, sea urchin, sea cucumber and especially, herbivorous fish, the primary consumers that are able to utilize the primary productivity most efficiently. They have been listed on many occasions as a priority to improve overall energy budgets. It is clear that for several species market demands, consumer preferences or restrictions are the driving force here. A good example is the milkfish, which is considered a staple in the Philippines but is not appreciated at all in many other Southeast Asian countries. Market researchers claim that there is room for improvement here, and this research challenge should be taken up very seriously, especially in Asia. The same applies to the molluscs, where further handicaps are health risks in consuming contaminated product, as a result of which interest is down in several species and regions (e.g. mussels in the Philippines). Suggestions are made to consider new approaches to increase the value of low-in-the-food-chain products, if not as food products maybe as dietary ingredients.

Fresh water becoming more and more a limited resource, air-breathing fish (clariid catfish and snakehead) are proposed as a valuable extension of the species list of freshwater fishes. Among the primary producers, seaweeds are clearly identified as still having a very important potential, not the least because their domestication is still at the very pioneering stages. As mentioned earlier, several research groups are exploring their possible role in large-scale nutrient recycling and even in increasing the capacity of the sea as a carbon dioxide sink. However, the search for, and development of, new utilizations of seaweeds, either as a source of fine chemicals and/or as an ingredient in formulated feeds, will be crucial here.

Let us turn now to research in genetics. All believe that for the next decade the real challenge is to get the aquaculture industries

  to introduce effective genetic improvement programmes using selective breeding. We are decades behind developments in the agricultural sector, where genetic research has resulted in huge gains in productivity. In recent times, milk production is up 150 percent, daily weight gains in pigs has doubled, and time to produce marketable broilers cut in half. The Norwegian salmon industry, where a lot of research money has been targeted in the past, has seen overall gains of 60 to 70 percent. Productivity of most other farmed species has remained almost constant, close to that of the wild founder stocks. Research is proceeding with several species of fish (carp, tilapia, trout, bream, bass) and molluscs (oysters, clams, abalone) and with others, like shrimp, work is barely starting, as very few species can be regarded as domesticated. The technical challenge is to close complex life cycles, not only with empirical culture techniques, but especially to understand how the nervous and the endocrine systems coordinate with the changing external environment. Once fully domesticated breeds are available and all factors for good genetic management of broodstock are fulfilled, the selection work can start. The importance of such a strategy of selective breeding is two-fold: first, it provides a sound population within which incremental improvements can be begun; second, much of this work is practical, and the sooner the industry people are involved the better the technology transfer and the closer to return on investment. Another point is that no other genetic approach offers continuing incremental improvement. The formation of improved selected lines provides a base population upon which, sooner or later, the additional advantage of other genetic approaches can be applied, on top of the incremental change. First priority is thus developing domesticated broodstock, still an art with some key species such as the penaeid shrimp, then followed by selective breeding schemes, allowing the production of certified seed.

The ability to use techniques in molecular biology to mark and identify stock by genetic fingerprinting will enable a much faster selection of advantageous traits. Highest priority in selective breeding programmes involves disease-related aspects. Two approaches are considered: disease-free as well as disease-resistant lines. Although no miracles are to be expected either, as good farming practices, optimal health management and appropriate measures of quarantine should not be neglected. Other factors of interest in selective breeding programmes are growth rate, market size and quality, food conversion ratios, fecundity and ease of domestication.




Although selection on a wide genetic base will give continued improvement, the development of monosex and polyploid strains can yield large gains.

The logical approach is to work for a combination of gains as is successfully done with genetically-male-tilapia (GMT) and genetically improved farmed tilapia (GIFT). Several of these strains have already proven their benefits; however, their impacts on the environment are not well-enough documented yet. Finally the use of transgenics or genetically modified organisms (GMOs) is a very sensitive issue indeed, especially since opinions are so extreme, with work ongoing and supported in some countries, completely halted in others. On one hand, public concern is at such level, at least in the western world, that the products will have to be proven safe for consumption and for the environment three times over. Let me warn you, however, that perceptions of safety are equally as important as safety itself. Proper testing is essential here. It seems likely that public debate will increase on this front and that the well-publicized precautionary approach with strict application of “performance standards” developed as a guide for researchers, will be adopted with absolute priority. The main danger seen is less one of health, but more of the maintenance of biodiversity through effects of escapes into the wild. In this respect, the often proposed need for gene-banking of aquatic organisms should receive a higher priority.

In any case, the development of transgenic aquaculture organisms is not expected to proceed so fast as some are claiming. The utility of any transgenic work is dependent upon inserting genes into individuals and having the insertion stable so that it is inherited. The expression of genes is dependent upon the genetic background into which they are inserted. That, and their continuance in a breeding population, means that there has to be a sound domesticated population into which they can be introduced for them to be effective. That is another reason for ensuring that industries establish sound selective improvement programmes first.

Let us now turn to research priorities in culture systems and techniques. Although pond cultures make up by far the most dominant form of aquaculture, still very little is understood about pond ecosystem functioning. It is time to plan more studies on nutrient dynamics in the water, the soil and their interactions, as well as the role of microbes in these processes.

  One could explore the potential to increase primary and secondary productivity, for example, by providing extra substrate as with the new idea of aquamats used in fish and shrimp farming. In fact, a very similar approach has been applied for decades in some traditional estuarine and coastal fisheries: the acadjas in Cote d’Ivoire and the katha fisheries in Bangladesh and India, where extra substrate suitable for colonization by periphytic flora and fauna results in increased food supplies. It is very likely that more research on pond-culture systems could improve the economics of the production and especially, ensure better environmental sustainability.

In view of the need to move mariculture more off-shore, extra research is needed on open sea-cage farming: equipment and materials, knowledge of fish behaviour, use of submersible lights to adjust photoperiod to control cycles of growth and maturation, and integration with seaweed and mollusc farming, as practised, for example, in Chile.

Recirculation technology will receive much more attention, as it offers lots of opportunities for captive markets and for safe applications with GMOs, as absolute guarantees can be provided to prevent escapees. Systems need to be further improved in order to make the production more efficient to be able to deliver competitive products for the market.

Consider restocking and stock enhancement: beneficial effects are well documented for confined areas such as lakes and reservoirs and for benthic organisms. However, more research is needed with pelagic species in the marine environment. Focus needs to be on how to make fish juveniles more fit for life in the wild, on releasing strategies and on their possible impact on wild populations. Most needed are validation studies, which can be better planned now that appropriate tagging and genetic marking techniques have become available. Also, the matter of artificial reefs and offshore drifting nets requires more attention. Can we better document increased primary productivity, or is it the sole effect of an aggregation of the fishable stocks?

As aquaculture feeds often make up 50 percent and more of the production cost, it is clear that research in this field will remain a priority. The nutritionist is to develop economical feeds, and here the concerns around the availability of fish meal and fish oil are paramount. Although some claim that we are OK for another one to two decades, many others are not as optimistic. Who can guarantee that global meal production will remain high? What about the sudden increase of fish meal consumption in aquafeeds in China?




As I explained earlier, a gradual conversion is taking place in China of extensive freshwater fish production to semi-intensive systems using pelleted feeds. The search is on for alternative protein and lipid sources. Plant-based protein sources are highest on the list; rendered products could be valuable, although the human health concern will require careful study. Single-cell proteins and by no means least, the recovery proteins from the waste of seafood processing and from fisheries by-catch are also important alternate protein sources. Disease issues that might be involved with this approach also need to be understood. Of course, these substitutions will require supplementation to fulfil the essential amino acid balance and essential fatty acid requirements.

Microbial products might alleviate demands for selected amino acids and fatty acids of the n-3 and n-6 series. Before this can become a reality, production must be increased, supplies must be stable and prices must fall to a competitive level. Improved nutrient availability should optimize the digestible protein to energy balance, but also be effective for maintaining good health and improving disease resistance. Finally, the so-called eco-friendly feeds, more nutrient-dense diets that allow for the reduction in phosphorus and nitrogen waste output, will further gain in importance. Progress in diet formulation is a must, but improved feed management is another field where research could contribute to more environmentally friendly productions: development of regimes that lead to reduction in losses from unconsumed feed and use of interactive feeding systems, to mention a few approaches. Consumer preferences will have to be better considered, as diet and feeding practices influence attributes of the farmed fish - their nutritional quality, texture and flavour. Further progress is also required with the starter feeds: use of less live food could be further improved and made more predictable. One could consider better-selected and eventually, manipulated strains of algae, rotifers and Artemia. Another need is more diversity in Artemia resources. Also required are improved formulations and manufacturing of micro-diets for use in co-feeding and full substitution of live food.

With annual losses of several billion US dollars caused by diseases in aquaculture, it is clear that this is another area of high research priority. However, first we should realize that we need to leave behind the decade of disease treatment with all the negative environmental and other consequences, and move to a future of disease prevention.

  Disease control in aquaculture should focus first on preventive measures related to good management practices that maintain good water quality, with better/certified seed, less stress, high-quality feeds etc. In many, maybe most, farming practices, there is still plenty of room for improvement on many of these counts. More applied research should better document these effects. We still need to acquire a lot more basic knowledge of the microbial, viral and parasitic diseases and their epidemiology in aquatic organisms. Access to a large arsenal of molecular techniques will certainly assist in quick progress in this area.

Development and validation of appropriate diagnostics has high priority. However, whilst PCR-based kits are very sensitive and can detect very small quantities of organisms, in the wrong hands they are very dangerous, as false positives and negatives are common from non-standardization of techniques, contamination etc. Lack of time does not allow me to further elaborate on research needs for vaccine development, quarantine systems and basic immunology research, especially in invertebrates.

Because of our preliminary research experience with microbial manipulation in larviculture systems, I would like to mention here that I expect important progress in the study of microbial processes and their regulation in many aquaculture systems. Competitive exclusion is one of the ecological processes that allow manipulation of the bacterial species composition in the water, the sediment and the animals’ digestive tracts.

It is a shame that I don’t have enough time left to cover regional differences in research priorities. However, one continent I want to at least mention is Africa, considered by many as the sleeping giant in aquaculture. Experts agree that the approach of the past - to adapt foreign technology - has failed. The way forward would be to research the indigenous knowledge base in Africa which has been largely neglected. Furthermore, one should develop economic options that are needs based and demand driven.

I mentioned earlier that extension of research results has to be better considered, as there are too many failures in technology transfer. We need more adaptive research: partnerships between the farmers and various service providers. Researchers need to realize that we have the responsibility to prove our research findings.




Furthermore, researchers often might not realize that, depending on specific circumstances, social and economic factors may be more important than technological factors. More interdisciplinary interaction will pay off, as is illustrated by recent aquaculture progress in the Mediterranean through various schemes of support by the European Union (EU) for joint initiatives between the private sector and the research community. Furthermore, North-South and especially South-South R&D interactions and networking are to be much more stimulated.   Today, we live in a small world with unique opportunities for communication and inter-action. I am also convinced that, in the field of aquaculture, humanity has an opportunity to better benefit from the historical differences. The diversity of our cultures and ways of thinking (for example, with regard to identifying research priorities and performing research and extension), the diversity in aquaculture farming practices and the differences in consumer interests - all can help us to understand aquaculture principles better and to consider better the challenges for the century to come.