SENAT

Report n° 132 (2008-2009) by M. Marcel-Pierre CLEACH, Senator (for the parliament office for the evaluation of scientific and technological choices)

Disponible au format Acrobat (822 Koctets)

IV. AQUACULTURE: FROM MIRAGE TO MIRACLE

Faced with the fishing crisis, with fish representing the last great wild biological resource to be exploited for human food, many see aquaculture as the natural and inescapable solution, just as man has shifted from hunting to breeding and from gathering to farming.

And yet, if aquaculture is indeed crucial for the future of human food production, its current form does not yet offer sufficient guarantees with regard to sustainability and may seem to offer false hope. For there to be a miraculous "blue revolution", a certain number of conditions must first be met.

A. AQUACULTURE: A NECESSARY FOOD SOURCE AT THE WORLD LEVEL

Based on worldwide halieutic-production statistics, aquaculture would appear to be not only an immediate necessity, but also a future pressing obligation in order to ensure food production for a human population that is ever growing and ever more eager to eat fish.

1. Aquaculture today: a necessary food source

According to FAO statistics (SOFIA 2006), aquaculture is the fasting growing animal-based food-production sector, posting an 8.8% increase per year since 1970 , compared to only 1.2% for fishing and 2.8% for terrestrial systems.

In 2004, aquacultural production reached 45.5 million tonnes for a value of $63.3 billion , and 59.4 million tonnes and $70.3 billion if one also includes aquatic plants. China represents more than 70% of the total tonnage and more than 50% of the total value. The Asian Pacific region accounts for 91.5% of the worldwide tonnage and 80.5% of the worldwide value (99.8% of plants, 97.5% of cyprinids, 87.4% of shrimp and 93.4% of oysters). Salmonid production is the only aquacultural sector dominated by Europe (55%). In Africa, aquaculture is concentrated within the Nile Basin, with Lake Victoria for perch and Egypt itself for the tilapia (second only to China) and the mullet (number one worldwide producer).

Within these global figures, it should be pointed out that freshwater aquaculture remains dominant (56.6% of volume and 50.1% of value), with carp alone representing 40% of the total tonnage . Carp production is traditional in China, where it is associated with rice farming. Indeed, bovids requires 7 kg of fodder for every 1 kg of meat, compared to only 3 kg for carp, and their production does not necessitate the requisition of arable land. Therefore, carp farming saves both cereals and agricultural land.

Nevertheless, while aquaculture represented only 3.9% of halieutic production in 1970, it represented 32.4% in 2004 . The aquacultural supply per inhabitant grew from 0.7 kg per year in 1970 to 7.1 kg per year in 2004.

Concerning fish produced for human consumption, worldwide aquaculture (excluding China) produced 15 million tonnes, compared to 54 million tonnes for fishing. In China, aquaculture represented 31 million tonnes, compared to only 6 million tonnes for fishing .

For the moment, in terms of species, aquacultural production remains extremely concentred, with 10 large groups accounting for 90% of production, although aquaculture is becomes increasingly diversified. The two largest groups are carp and shrimp. Of this production, saltwater fish represent only 1.4 million tonnes .

At the global level, aquaculture provided 43% of the total volume of table fish in 2004 .

Aquaculture plays an essential role in the food security of numerous developing countries , starting with China and India, the world's two largest producers. In China, the supply per inhabitant rose from 10.9 kg in 1994 to 23.7 kg in 2004.

While aquaculture is a major source of world food production, one must not mistake its true nature.

The current form of aquaculture relies overwhelmingly on freshwater fish. Very few marine species are farmed; their production is negligible compared to the world sea catch. Therefore, with regard to world food production via marine resources, it offers no alternative to fishing .

This aquaculture is highly concentrated geographically, nor does it represent a viable alternative to the European fisheries.

The small number of concerned species and their often mediocre gustatory quality would represent an important setback in terms of biodiversity and food quality compared to the wild-fish catch.

2. Developing aquaculture: an obligation for tomorrow

For the past 20 years, the world catch volume has stagnated, as has already been mentioned; it is even possible that it has already started to decline.

At the same time, worldwide per capita consumption of halieutic products is increasing, rising from 9 kg in 1961 to 16.6 kg in 2004.

In the continental or inland waters (China included) , aquaculture already represents more than three times the volume of the freshwater fish catch (28.9 million tonnes compared to 9.6 million tonnes). At sea, the fish catch is around four times as great as saltwater aquacultural production (84.2 million tonnes compared to 18.9 million tonnes), but the gap is narrowing. Indeed, 2008 is expected to be the first year in which aquacultural production will match fresh- and saltwater catches for human food production.

Considering the much deteriorated state of the marine fish stocks, we can expect no increase in catches. Hardly any virgin stocks remain, with most stocks being fully exploited or even over-exploited.

Therefore, only aquaculture will be able to meet the future demand for halieutic products and fill the gap between fish consumption and the wild fish catch.

In addition, in its forecasts for 2030 , the FAO counts on a stable marine catch (87 million tonnes), only a slight decrease in the inland catch volume, and a marked increase in aquacultural production , which is expected to reach 83 million tonnes . The FAO predicts that aquacultural production will continue to increase at the very high rate of 8% per year worldwide. This would allow table-fish production to reach 150 million tonnes, which is nearly equivalent to a 50% increase compared to the 2004 volume of 105.6 million tonnes.

According to its forecasts, over the next 20 years, aquaculture will account for the greater part of table-fish production .

At the same time, the FAO estimates that the share of total production used for consumption will increase (to 85% instead of 75%), with the volume dedicated to non-food uses decreasing by one third, dropping from 34.8 million tonnes to only 26 million tonnes . This represents a bold bet on the ability of aquaculture to depend upon an ever decreasing amount of wild or non-farmed products , for we would witness a near doubling of production along with a one-third reduction in the amount of "wild" inputs.

The FAO is perfectly aware of the challenge constituted by this forecast and recognizes that, at least until 2015, the demand for fish meal will continue to increase along with the pressures on this market and therefore on the wild resources. After this date, it believes that the research under way will be able to begin to produce its fruit and will rapidly help to alleviate demand.

However, the FAO believes that the rising cost of fish meal could slow aquacultural growth and could even result in a decreased volume of table fish starting at the end of the present decade.

3. French marine aquaculture: a strategic issue

According to the Poseidon Report, French marine aquaculture presents distinctive characteristics: the sector's highly technical and competent nature "upstream" and the marked preponderance of shellfish farming (in particular, oyster farming; French oyster farming accounts for 90% of European production and represents the number one aquacultural activity in terms of value at the national level, coming in second at the European level). However, France counts very few marine fish farms .

In our country, the major obstacles to this sector's future development are the conflicts of use and the difficulties of obtaining administrative authorization. The solution, no doubt, resides in a national inventory of favourable sites (already carried out in 2001 by IFREMER) and its incorporation into the coastal development and management plans.

French aquaculture is specialized in a small number of shellfish species farmed by small businesses. This makes the sector especially sensitive to health incidents, as was illustrated last season. IFREMER's aquacultural research logically concentrates on shellfish (in particular, hatcheries, so as not to depend upon the capturing of wild seed oysters, heavily concentrated in Arcachon Bay) and on resistance to diseases and the development of alternative species in the event of a new epidemic. Shellfish farms are also highly dependent upon water quality and terrestrial effluents.

However, French marine fish farming is very limited, with an annual production of around 7,000 tonnes. Nevertheless, French hatcheries are successful, producing over 60 million alevins (over two thirds of which are exported), accounting for one quarter of the sector's turnover. Production is concentrated on three species: sea bass, turbot and bream.

This situation is hardly satisfactory, especially considering its paradoxical nature. We are importing ever greater quantities of farmed fish and shellfish, while at the same time deploring the conditions in which these same fish are raised and preventing the development of a downstream sector in France.

Considering the international stakes of aquaculture and the evolution of fishing, the development of the French aquacultural sector represents an important issue for the future with regard to both national food production and coastal economic activity .

What is more, the various aspects of the strategic importance of aquacultural development have been well identified by the French authorities:

- Guarantee favourable sites for marine fish farms.

- Ensure good water quality , even if this task remains difficult and though protected marine zones located directly offshore will offer new means of control.

- Develop the downstream fish-farming sector.

- Diversify the species farmed and strengthen protection against diseases.

B. A NON-SUSTAINABLE AQUACULTURE

Necessary and inevitable, aquaculture would appear to represent a "blue revolution" similar to the "green revolution" which saw an increase in agricultural production beginning in the 1950s and which has allowed numerous countries to avoid a food crisis . 25 ( * )

While certainly constituting a revolution, we are nevertheless far from the aquacultural miracle that is sometimes described: not only would aquaculture provide us with food, it would also render fishing unnecessary and minimize our environmental impact. Unfortunately, this radiant picture is inaccurate and can still be likened to a mirage.

1. The impact on the "wild" resources

Most aquacultural fish and all maricultural fish are carnivorous; in their natural environment, these superior predators feed on other fish. In captivity, they must be provided with their prey, in the form of fish meal and oil.

This fish meal and oil are made from the non-food forage fish catch , generally small pelagic species such as anchovies, jack mackerels, gilt sardines and sand-eels from the North Sea. However, this fish-meal catch of some 35 million tonnes is not dedicated exclusively to aquaculture (46% of meal, 90% of oil), for the use of fish meal in poultry farming (22%) and pig farming (24% 26 ( * ) ) continues despite the strong rise in the prices of these inputs.

It is generally estimated that one tonne of fish is needed to produce 200-250 kg of meal and 40-50 kg of oil .

World production has reached its ceiling of 6-7 million tonnes of meal and 1-1.7 million tonnes of oil.

The production of fish meal and oil and worldwide aquaculture are completely dependent upon a few highly targeted halieutic resources , the most important of which is the Peruvian anchoveta and a few other species of the Humboldt Current. Peru provides 30% and Chile 15% of total world production; therefore, 45% of total world production is dependent upon the management and productivity of a single ecosystem! An additional 40% is provided by only seven countries.

In addition to this dependency, there is the negative yield of superior-predator farming. Today, it is estimated that in order to produce one kilo of farmed fish (such as salmon), some 3-5 kg of wild fish are needed . However, this yield is positive for the farming of freshwater, herbivorous or omnivorous fish (such as milkfish, tilapias, panga and carp), with only 0.2-0.3 kg of wild fish needed to produce 1 kg of farmed fish.

The problem of meal-fish production is not limited to the question of aquacultural profitability.

Two other important issues must also be considered. Firstly, the direct use of some of these resources as food . While this was largely a non-issue in the case of the Peruvian anchoveta, since traditionally this species was not fished for and consumed, it is already an issue in other regions of the world where this pelagic fish could serve as a basic table fish, in particular for the poorest populations. In Peru itself, the act of transforming some ten million tonnes of perfectly consumable fish into meal for exportation, while the country's own population can still suffer from malnutrition, is a subject of debate. Indeed, the Peruvian authorities have decided to launch campaigns promoting the domestic consumption of this fish as food.

One must also consider the impact on the food chain . Forage fish that are transformed into meal play an essential role in ecosystem balance by eating plankton, which is thereby incorporated into the food chain. In addition, these fish are also the prey of all the other predators, whether fish, birds or mammals. Therefore, the fishing of forage species raises the question of the fish-meal catch's impact on the rest of the ecosystem.

In reality, this impact remains very poorly understood. The information available is disparate and fragmentary and leaves very ample room for hypothesizing. Commissioned in 2002 and 2003 by the European Commission, ICES produced an evasive assessment while calling for a better understanding of the subject matter. In 1997, it had estimated natural predation of the sand-eel in the North Sea at 1.9 million tonnes for predatory fish (cod, haddock, whiting, mackerel, pollock, coalfish and sea robins), 200,000 tonnes for birds and 300,000 tonnes for mammals and other fish. Seabirds' dependency on this prey is best understood, for forage fish constitute an indispensable source of lipids during the reproductive period; this has led to the creation of a 20,000-square-kilometre fishing reserve to the west of Scotland. In Peru, one observes the same dependency of seabirds vis-à-vis anchovies, as well as decreasing populations.

Even more poorly documented is the long-term impact of such a large biomass's withdrawal from the ecosystem.

Finally, the exploitation of these forage fish is rendered all the more delicate by the limited longevity of the stocks, which therefore boast few age classes. While extremely prolific during normal times, these fish are very sensitive to climate changes and overfishing; the combination of a poor recruitment and overfishing can lead to the fishery's closure, with its ensuing chain of consequences on the ecosystem.

These mechanisms render aquaculture heavily dependent upon wild ecosystems, which are themselves subjected to very great pressure.

But wild resources are not impacted only by fishing; one must also acknowledge the existence of a genetic pollution .

The cages in which fish are farmed are never completely impermeable and numerous fish escape, thereby threatening to mate and form hybrids with their wild relatives. These fish contribute to the genetic weakening of the wild populations.

The best known cases concern the salmonids, which are specially monitored to measure their hybridization with the wild salmon of the rivers.

For example, in early October 2008, a 7 kg salmon was caught in the Seine at Suresnes. This event was enthusiastically greeted by most media outlets, for a salmon had not been caught this far up the river in 70 years. This "bioindicator" salmon was welcomed as signalling a significant improvement in water quality and the crowning achievement of water-quality measures. While this is undoubtedly true, one must not forget the environmental destruction that has made what would have been considered an ordinary catch at the beginning of the last century, quite an event today, nor the ban imposed by the prefect of the Haute-Normandie department on eating fish caught downstream due to the presence of PCBs. Nor should one forget that this salmon would undoubtedly have had trouble reproducing, for its having been caught at Suresnes is due to the fact that the Suresnes dam lacks a fish pass. Finally and most importantly, this salmon was a hatchery fish that had escaped from its cage several years preceding its capture. 27 ( * )

The escape of fish from their cages can have a more dramatic effect when the species is farmed outside its natural environment, in which case it becomes invasive. In Chile, the rivers have lost their original fish population as the result of introductions dating from the 19th century and intensive fish farming.

2. The impact on the natural environment

In its current form, marine aquaculture also suffers from excessive discharges of food and pesticides. These two inconveniences are directly linked to the more or less intense nature of fish farming, as well as to its management.

The concentration of fish threatens excessive organic discharges into the marine environment, and even the terrestrial environment for the skins, heads and bones. These discharges are of two kinds: excess food and excrement. They can lead to a eutrophication of the sea bed; in other words, the depletion of dissolved oxygen due to increased decomposition and plant growth (phytoplankton, algae).

Overpopulation is also a powerful vector of diseases , some of which may be vaccinated against. For example, in Norway, all farmed salmonids are vaccinated by hand. Other diseases, however, may lead to the poorly-regulated use of antibiotics and other medicines, which are then diffused throughout the environment. Farmed fish can also have parasites , such as sea lice on salmon, which they pass on to their wild brethren.

In Chile, environmental associations report that the county's intensive salmon farms have had to relocate far south to virgin zones due to the impossibility of controlling diseases and the environmental destruction of the initial maricultural zones which have become unsuitable for fish farming.

C. THE ENVIRONMENTALLY FRIENDLY AQUACULTURAL OPTIONS

Despite these very great limitations, aquaculture remains a promising sector if it truly helps to protect certain threatened species and if it manages to reduce its environmental impact and the pressure it exerts on the wild fish stocks.

1. A role in the preservation of wild species

Aquaculture could be the only solution to save a certain number of threatened, wild species, just as certain land animals are the subject of international breeding-in-captivity programmes within zoos, in order to first save and later reintroduce these species back into their natural environment.

Most progress has undoubtedly been made with regard to sturgeon and eel farming.

The former was ignored until the discovery of the method for producing and the culinary popularity of caviar, while the latter was scorned and occasionally used as fertilizer. Both species migrate between the sea and freshwater and both are today seriously endangered. Sturgeon and eels are the subject of research for their farming and reproduction.

Sturgeon , which produces the different varieties of caviar, is one of the world's most threatened species of fish, the victim of an anarchical system of fishing in the Caspian Sea since the collapse of the Soviet Union. The very high prices fetched by wild caviar and the partial ban on its commercialization have opened the way to the farming of a few species in order to satisfy demand and relieve pressure on the surviving wild populations. Sturgeon farming has become a very famous French speciality. Aquacultural research has also concentrated on the European species once common in France's Gironde department and in other European waterways. This species has been protected in France since 1982 and at the European level since 1988. Since 2007, after 15 years of breeding, several reintroductions have been carried out in the Garonne and Dordogne Rivers. At the same time, in 2008, several releases were carried out in the Elbe River, from which sturgeon had been absent for at least fifty years. New European partners will undoubtedly allow for a wider European reintroduction effort in the future. This project is currently being carried out by CEMAGREF in Bordeaux and the Leibniz Institute of Freshwater Ecology and Inland Fisheries in Berlin.

Less progress has been made with regard to eels . European eel stocks are today exhausted, victims (along with all other migratory diadromous 28 ( * ) fish) of poor freshwater quality, development and the destruction of spawning zones . The case of eels is rendered more complex by the fact that we still do not know how to breed this fish in captivity . All farmed eels have been caught as wild elvers in our estuaries. Indeed, in its natural state, the European eel is never sexually mature in our rivers. It is during its journey back to the Sargasso Sea, where the eel will reproduce and die, that it becomes sexually mature and its body is radically transformed and mobilizes all of its resources for reproduction. Producing individuals capable of reproducing therefore entails various complex stimulations simulating the effects produced by the fish's Atlantic migration. One must then succeed in raising the alevins, by providing them with the physical conditions and prey that they would naturally find in the Sargasso Sea at the time of their hatching. During my investigations, I have been able to observe very encouraging experiments that lead me to believe that researchers, particularly in Denmark and Japan, are about to succeed in the laboratory. Combined with other efforts, aquacultural research could perhaps allow the wild species to regain its historic abundance.

2. Reducing the impact on the natural environment

Reducing the impact on the natural environments in which aquacultural cages are set up represents a second challenge. To succeed, all farming methods must be improved.

Excess nutriments in the water and sediment are the first obstacle. A variety of solutions could be implemented: reducing the nutriment supply, changing the fish food, reducing densities, or even setting up closed fish farms with recirculation . Though complex and costly, the latter certainly represent the future of aquaculture, at least in freshwater , for they guarantee complete control of the fish-farming process. For mariculture, the question of cage location is also being considered in order to ensure proper discharge dispersal; one option being studied is the setting up of fish farms on the high sea, where all pollution would be eliminated by the currents. An important avenue of research is also the mixed farming of multiple species; for example, filter-feeder molluscs farmed alongside fish cages or combinations with other fishing activities, with artificial reefs that would provide habitat to a greater density of fish benefitting from the excess nutriments.

The excessive use of antibiotics has also been identified as the cause of increasingly resistant bacteria in fish-farming zones , prompting first a decrease in biodiversity due to the spread of disease, then the abandonment of the farm, the strains becoming too resistant. Here, the solution resides in a preventive approach which seeks to avoid the unexpected appearance of disease via an appropriate environment and diet, a vaccination, greater surveillance and, perhaps, isolated treatment systems.

Other, more specific problems must also be considered, such as the use of new habitats for shrimp farming in order to avoid the destruction of mangroves, which has a dramatic impact on biodiversity and the tropical coasts. The same is true for excesses linked to shellfish farming, which can result in a decreased biomass of phytoplankton, a decreased number of natural seed oysters, or excessive discharges.

3. Reduce or eliminate the catching of wild species

Finally, reducing or nearly-eliminating the catching of wild species will first entail the choosing of species more in accordance with this priority and the farming of omnivorous or herbivorous species whose yield is markedly greater though often of lesser value.

For the carnivorous species, extensive studies must be carried out to further reduce the amount of fish meal and oil in the diet of these farmed fish . For the time being, this is very difficult, for farmed fish lose the nutritional qualities (fat content, fatty acids, etc.) that make them interesting, if they are not fed a sufficient quantity of halieutic elements, in which case they also lose their gustatory qualities and, in some cases, the physical appeal of their meat. In addition to these problems, there is the increased risk of disease during farming and, in the longer term, of the denaturation of carnivorous animals that have become herbivores, similar to cattle that are fed animal meals.

To find a substitute for fish meal and oil, IFREMER's André Gérard discovered that animal meals and oils were initially favoured by fish farmers. Animal meals present a good amino-acid content, but they also contain lipids of poor quality for fish and too much bone-based mineral material. Animal oils are too rich in saturated fatty acids. They were progressively abandoned and finally banned in 1996, though they are still used in Asia.

Aquaculturalists have therefore turned toward plant-based food sources. Plants can provide amino acids similar to fish meals, though in different proportions. In most cases, they must therefore be mixed to obtain an adequate nutritional profile as fish food. In addition, in order to avoid antinutritional factors affecting digestion or disrupting natural hormonal functions, a sorting out or a specific treatment must be carried out. Finally, since fish have great difficulty metabolizing carbohydrates (unlike shrimp), oil cakes or gluten are required. It turns out that, in total, these plant-based substitutes cost about as much as fish meal. The advantage is that, at the experimental level, a replacement rate of 75% can be reached with trout and sea bass, without any detectable effect on the growth or quality of the meat (compared to the current replacement rate of 30-50%). The use of plant meal should also allow for a decrease in the quantity of mercury found concentrated in certain meals.

Vegetable oils are exceptionally well suited to replace fish oils, which can be reduced to only 2-4% during farming. Vegetable oil has the added advantage of very markedly decreasing the concentrations of lipophilic pollutants, such as dioxins and PCBs, which become concentrated in the marine food chain. However, this diet modifies the meat's omega-3 content, which is incorporated but not synthesized by fish. It is therefore indispensable to provide these fish at the end of their farming life cycle with a diet rich in fish oil.

In addition to this research on fish food, researchers are searching for fish that will better accept this modified food and be better suited to intensive aquaculture.

The goal is not only environmental in nature: fish meal and oil together constitute a limited resource, since the fish catch will not increase in the future. This resource will therefore be directed toward the most productive and profitable use. It can be supposed that the use of these meals to feed poultry and pigs will be abandonned to the benefit of aquaculture, for they are not required by land animals. But it may become more profitable to transform these small pelagic fish and fish waste into end products directly destined for human consumption, such as surimi or "fish-grade fish".

The stakes of this research are therefore fourfold:

- Relieve pressure on the wild fish stocks and preserve the natural environment.

- Lower food costs.

- Guarantee consumers food security.

- Guarantee the organoleptic quality of food.

* 25 For Science, no. 373, November 2008, Jeffrey Sachs, Director of the Earth Institute, University of Columbia, New York.

* 26 2003 figures, source: IFREMER, André Gérard.

* 27 See Le Chasseur français, December 2008.

* 28 Fish dividing their lives between fresh- and saltwater (living in one and reproducing in the other, depending on the particular species).