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)
|
NO. 1322
CONSTITUTION OF 4 OCTOBER 1958 THIRTEENTH TERM |
NO. 132
REGULAR MEETING OF 2008-2009
|
|
Registered with the Presidency of the National Assembly on 11 December 2008 |
Appendix to the minutes of the 11 December 2008 session |
PARLIAMENTARY OFFICE FOR THE EVALUATION OF SCIENTIFIC AND TECHNOLOGICAL CHOICES
REPORT
on
"Science's contribution to the evaluation of halieutic resources and to fisheries management"
by Mr Marcel-Pierre CLEACH,
Senator
|
Filed with the Bureau of the National Assembly by Mr Claude BIRRAUX Chairman of the OPECST |
Filed with the Senate Bureau by Mr Jean-Claude ETIENNE First Vice-Chairman of the OPECST |
||||
INTRODUCTION
"Sea fishing is free ,
for it is impossible to exhaust marine resources"
Grotius, 1609
"A marine ecosystem is not an organism, it has no final function.
It can be a viable assemblage of abundant and prolific species
or a desert of mud, home to jellyfish and gobies."
Philippe Cury and Yves Miserey, 2007
Ladies and Gentlemen,
The role of the fishing industry is often summed up by way of a comparison: in the agricultural sector, it could be considered equivalent to tomato farming; in other words, of very little consequence to the French economy as a whole. If one also considers the fact that 85% of the fish consumed in France is imported, the French fishing industry appears as a marginal sector in little position to attract the attention of the public authorities, outside the occasional social crisis. Faced with such an apparently minor economic activity in constant decline, one might be expected to let the subject drop.
But can fishing be limited to the above considerations?
Certainly not, for fishing is an essential activity , in the literal sense of the term; in other words, a distinctively human activity from the very beginning . Like hunting and farming, fishing is a fundamental subsistence activity for predaceous, omnivorous man shaping his environment. Indeed, this particular form of hunting and gathering is as old as our species.
Moreover, fishing continues to play a fundamental role in human sustenance, providing the world population with 20% of its animal proteins and representing the main animal-protein source for some one billion men and women , essentially in the Southern Hemisphere.
Fishing is also essential because it constitutes a considerable harvesting of the Earth's "living production". Although not a form of farming, the fishing of wild stocks is becoming equivalent in scale and directly raises the question of its own sustainability. Indeed, when one examines the world's oceans, "mortality by fishing" - to use the scientific term - today dominates, outranking all other possible factors.
However, on a blue planet, 70% of which is covered by oceans, man has reached the limits of its exploitation . The oceans, which had previously seemed immense, inexhaustible and all-absorbing or all-tolerating, have now also become a finite universe , whose limits are set by the capacities of man and which is therefore subject to management . Less understood than even terrestrial biodiversity, marine biodiversity is a resource and asset for humanity whose importance and precious, unique and, indeed, irreplaceable character we are only now beginning to appreciate.
This is a cardinal point, for if through fishing we are reaching the limits of the oceans, we are also approaching an essential limit of the Earth's ecosystem .
Today, man is also forced to manage the oceans because the maritime fisheries are in crisis . Although this crisis was expected due to the overcapacities and obvious weaknesses of the management methods in place, it is no less serious for the fishermen affected, especially considering the exacerbating rise in fuel prices. These actors are more often than not the victims of an evolution beyond their control, caught up in the spiral of having to continue fishing to make their living, whatever the costs.
The general public has not been spared this fishing crisis now occupying the media's attention. This is evident at several levels, first and foremost with regard to the public's pocket book. The price of fish is rising and the public is the first to suffer. The public is then asked to consume responsibly by referring to a list of approved fish and fishing grounds so as not to buy any boycotted products. As can be seen at any fishmonger's, the fish available for purchase today are no longer the same: there are new, unknown species from distant or deep fisheries and mass-produced, inexpensive products from aquaculture. There are also those fish that are becoming increasingly rare and expensive. Finally, there is a rash of labels indicating origin, fishing method and geographic zone. While very much present at the fish stand, the crisis is difficult to decipher and understand.
This essential industry undergoing a prolonged crisis also stands out for being one of the most scientifically-controlled economic sectors . There is certainly no other sector, excepting that of high-technology, whose nature and volume are determined by scientific assessment. Total allowable catches (TAC), quotas and other management systems are the result of political decisions based on scientific data. Indeed, some believe that the fishing industry is or should be "science-driven".
The time has come for the political class and, in particular, for a member of Parliament belonging to the Parliamentary Office for the Evaluation of Scientific and Technological Choices (OPECST) to consider the role of scientists and experts in the public decision-making process . What should this role be? Should the scientific assessment be literally transcribed? Or is it instead flexible? If so, depending on what factor(s) and to what extent?
It is striking to note that within the fishing domain, no party seems satisfied by this scientific assessment. Scientists are unhappy because they consider themselves insufficiently respected, even completely ignored or scorned. Fishermen complain that their point of view does not receive sufficient attention and has little effect on the decisions made by scientists who, they claim, do not know the sea. Finally, NGOs seem to have rallied to the scientists' side against the fishermen and politicians and call upon public opinion to witness to the situation.
However, on what are managerial decisions to be based if not scientific data? Who are to decide public policy if not the elected representatives responsible for looking after the general interest?
In addition to these questions of fundamental importance for our modern societies, there are those concerned with the management of natural environments. Fishing represents the last great hunting-gathering activity carried out in wild nature. This was long a free, unrestricted activity, with fishermen removing as much as they could from an infinite resource. This is no longer the case. In several regions, fish stocks seem to have been exploited beyond a reasonable extent, thereby endangering the species. The fishing crisis also means that there is no longer any wild territory on Earth on which man's actions do not have a decisive impact. Today, all regions have been anthropized and among all those elements external to any given environment, man has the greatest impact. While the development of fishing is now nearing its limits, the demand for food by an ever-growing human population remains a strong source of pressure. Is fishing, like its terrestrial predecessors, doomed to disappear as a habitual source of sustenance?
One set of questions raised concerns the possibility of a "sea without fish" 1 ( * ) . Is this outcome as near as it is inevitable? Can man afford to take this risk? How would the destruction of the marine environment affect the human race?
Another set of questions concerns possible alternatives. Can aquaculture replace fishing , just as animal husbandry succeeded hunting and gathering? Many believe so. Indeed, according to statistics and forecasts of the United Nation's Food and Agriculture Organization (FAO), this scenario is unavoidable. For the past two decades, aquaculture has accounted for all growth made in fish production. This trend is expected to intensify, with the fisheries remaining at their current maximum production and aquaculture representing by 2030 a source of production as great as fishing and providing the greater part of man's fish-based sustenance. However, is this realistic with today's aquaculture? Is it desirable?
Your rapporteur has undertaken this report commissioned by the Bureau of the Senate in order to answer all of the above questions, as well as to meet a certain transgenerational responsibility . The sea, fishing and wild fish constitute a tradition, a civilization and a taste that together form a heritage that must not disappear . Finally, fishing plays a major socio-economic role in several French regions.
*
The questions raised by fish management are not only global in scale. They are also concretely embodied at the French and European levels. Since 1983, the fishing industry has been the subject of a common policy (the Common Fisheries Policy or CFP) set by the European Commission via a negotiation with the member states. This policy is at the heart of important, lively debates. The main actors, starting with Commission Member Joe Borg, are perfectly aware of its limits and would like to overhaul the policy. What is more, in a recent document, the European Commission approved the immediate and complete revision of the CFP. The present report is meant as a contribution of the French Parliament to this European-level debate and reflection, with a view to the publication in early 2009 of a document to serve as the point of departure for a wide-based consultation among EU member states and the concerned parties. The stakes are too high for us to choose not to rise to the occasion.
*
It is worth clarifying the subject matter of this report. The term "halieutic resources" employed by this report could be misconstrued as taking into account freshwater resources (rivers, lakes, etc.) as marine resources. However, for the sake of clarity, it seemed more logical to here concentrate on the principal consideration: marine resources. The situation of freshwater species and continental or inland fishing depends upon a different set of issues.
However, it also seemed pertinent to include marine and coastal aquaculture in the present report. In the current context of stagnating world catches, it is aquaculture that is meeting the markets' ever-growing demand for fish. This sector is often seen as a panacea and constitutes a new frontier of research, as much for food production as for species conservation.
*
Within this framework, your rapporteur will first present a quick overview of our knowledge of the oceans. I will then analyze the situation of the world's fisheries, before painting a more precise picture of the French and European fishing grounds. I will then conclude this report by considering the real prospects offered by aquaculture and by the measures that could be recommended to remedy the current situation.
*
Before moving on to the report proper, your rapporteur would first like to take the opportunity to thank the scientists and various administrative services, both French and foreign, as well as representatives of the fishing and shipping sectors, with whom I was able to meet and who shared with me their analysis of the global fishing situation. These many meetings allowed for the formation of a diagnosis, of which this present report is the result. I would especially like to thank Philippe Cury, Director of the Centre de Recherche Halieutique Méditerranéenne et Tropicale ("Mediterranean and Tropical Halieutic Research Centre" or CRH) in Sète, whose work has played an important role in my consideration of this subject.
I. THE OCEANS DURING THE "ANTHROPOCENE" PERIOD
According to Paul Crutzen, the Dutch winner of the 1995 Nobel Prize in Chemistry, the Holocene period has come to an end. This geological epoch covering the past 10,000 years was first defined during the International Geological Congress of 1885 to describe an entirely new period of time marked by humanity's transformation from a nomadic, hunting-gathering society to a sedentary society practicing animal husbandry and agriculture.
According to Crutzen, the Earth has now entered the Anthropocene, a new era that began sometime around the late 18th and early 19th centuries with the Industrial Revolution. The Anthropocene is characterized by the decisive impact of man on the Earth's ecosystem. According to this view, man has become the dominant factor, outstripping all others that had previously prevailed. Having acquired the capacity to modify their environment, humans are thought to have an influence on world climate and to disrupt the balance of the Earth's biosphere. All over the planet, man's exploitation of natural resources and his environmental impact is considered to prevail over any natural factors and/or fluctuations.
Compared with the terrestrial ecosystems, the oceans enter the Anthropocene little understood and in a situation of deterioration.
Xavier de La Gorce, General Secretary of the French action at sea, sums up the situation of the oceans well when he writes: "Is it normal that today we know much more about outer space than we do about the sea [...] which alone covers 70% of the planet?".
Indeed, the oceans and their biodiversity remain infinitely less understood than the terrestrial ecosystems. Even the large emblematic species such as bluefin tuna, cetaceans, sturgeon and cod remain largely mysterious.
In the United States, the Joint Ocean Commission Initiative (JOCI) pointed out that while 400 men have climbed Mount Everest, 300 have entered space and 12 have walked on the moon, only 2 have penetrated the ocean depths, which remain the least explored of any territory. Deep-sea fishing has brought to the surface hitherto unknown species whose biology is little understood. Science lags behind fishing. Another example is offered by Claire Nouvian's 2006 book entitled Abysses 2 ( * ) . Nearly a third of the organisms photographed are unknown species whose discovery was made possible only by their chance encounter with the exploratory submarine.
Marine biodiversity is far from having been completely inventoried, including for the more well-known species. In the beginning of 2008, Bernard Séret, a researcher at the Institut de Recherche pour le Développement ("Research Institute for Development" or IRD), reported the discovery of twelve new species of sharks, rays and chimaeras between New Zealand and New Caledonia during a single month of exploration. During a period of fifteen years, 130 species of sharks had been described for the first time. In addition, this same researcher estimated that there undoubtedly exists between 1,500 and 2,000 species of sharks and rays, although only 500 have so far been identified. He explained that "Our current knowledge of sharks is based upon the study of only ten or so species. How can a fishery be effectively managed under these conditions?" 3 ( * )
Even while they remain insufficiently understood, the oceans, on the one hand, have been made vulnerable by global warming and manmade pollution and, on the other hand, are subjected to ever greater exploitation necessitating an ever more astute scientific management. This is felt directly by Fishermen, who view themselves as the victims of phenomena that are beyond their control, but the consequences of which they are often blamed for.
A. THE IMPACT OF CLIMATE CHANGE
Climate change impacts the oceans in multiple ways, which have long remained difficult to measure. It is not possible for your rapporteur to here enumerate all such effects. However, I would like to emphasize a few: acidification, desertification and species displacement, as well as chronobiological phase shifts.
1. Acidic oceans
Carbon dioxide present in the atmosphere is dissolved into the ocean, where it can be stored when the ocean serves as a carbon sink. This faculty of the oceans, considering their importance in the Earth's ecosystem, is a powerful factor of climatic inertia. But the absorption of CO 2 also results in the acidification of the oceans by increasing their concentration of hydrogen ions.
Since the beginning of industrialization, the oceans' pH has dropped from 8.2 to 8.1 and could reach 7.9 by 2100.
This situation could have serious consequences by 2030 for a certain number of organisms using carbonate for their shell or skeleton . For instance, a portion of "shelled" zooplankton, such as pteropods, could disappear in certain areas of the ocean due to overly-acidic water. This would also signal the disappearance of an essential link between the ecosystem's phytoplankton and its predatory fish. The same would hold true for deepwater corals - in particular, those off the coast of Europe - whose important role in the ecosystems we are only beginning to discover; two thirds could disappear by the year 2100.
These serious prospects remain the subject of scientific debate and the impact of acidification remains uncertain. Recent studies on a species of phytoplankton, the alga Emiliana huxleyi , tend to show that acidification does not necessarily entail a decrease in calcification. This very common species of alga is of particular interest because it uses dissolved CO 2 to carry out not only its photosynthesis but also to synthesize plates of calcium carbonate around its cell. A recent article by Debora Iglesias-Rodriguez et al. 4 ( * ) published in the revue Science pointed out that acidification could, on the contrary, lead to an increased calcification and primary production. However, the resulting organic matter would be richer in carbon. According to French scientist Antoine Sciandra (CNRS, oceanography laboratory of Villefranche-sur-Mer), the difference in laboratory results could be explained by the particular method used: the dilution of CO 2 , a method similar to natural conditions, rather than the hydrochloric acid method. 5 ( * )
2. The desertification of the oceans
A recent article by Jeffrey Polovina et al. published in the Geophysical Research Letters 6 ( * ) has shed light on an expansion of the ocean's "desert" zones.
This researcher processed data from the past nine years on the colour of the ocean provided by the SeaWiFS (Sea-viewing Wide Field-of-view Sensor), in orbit around the Earth since 1997. This instrument is capable of identifying those zones devoid of photosynthetic vegetation and therefore barren because lacking the very first element of the food chain. According to these results, the ocean's desert zones have grown by 6.6 million km² (15%) since 1998 , equivalent to twelve times the surface area of France. The most affected zone would be the North Atlantic, whose oceanic deserts would have grown by 8.3% per year.
These zones vary in size depending on the time of year, increasing during the winter.
This desertification could be explained by the warming of the surface layer of the ocean and a greater stratification, resulting in a decreased mixing with the deeper, colder layers rich in nutrients consumed by phytoplankton during photosynthesis.
However, the article's authors believe it impossible to determine whether this trend is entirely due to climate change and whether it will continue at the same rate in the future.
These results could just as well be interpreted as demonstrating an acceleration of the phenomenon as the intervention of other factors, such as a yet unknown, natural variability.
In any case, this issue is very important, because it could have a considerable impact on the abundance of halieutic resources, concerning as it does the very basis of the food chain.
It is the subject of in-depth international studies; in particular, a joint programme between CNES, ESA and NASA is currently being set up in the Mediterranean (Moose 2). Its goal will be to complement the optic satellite observations that are hampered by cloud cover and the atmosphere. Buoys will measure the state of aquatic life by collecting long-term data on the colour of the ocean.
3. Species displacement and chronobiological phase shifts
Fishermen increasingly remark that the contents of their nets are changing due to global warming. These variations go beyond the traditional fluctuations that are normally observed.
The first consequence of global warming is a displacement of species to the north . A growing number of species from the subtropical zones or warm waters are seeing their populations increase in our waters. The most emblematic example of this phenomenon is the red mullet, now common in the English Channel and even in the North Sea.
However, certain species suffer directly from global warming and no longer find in our waters a zone propitious to their reproduction. The most famous example of this second phenomenon is the cod in the English Channel and even in a section of the North Sea. Too high temperatures prevent this fish from reproducing by killing its eggs.
Important Norwegian and Franco-Norwegian studies on Greenlandic cod and on the Barents Sea have allowed scientists to compare changes in water temperature, the cyclicity of Atlantic Ocean oscillations and the cod's food chain. In 2004, Johannenssen et al. were able to demonstrate that since the year 1900, the distribution of cod along the eastern coast of Greenland has varied according to temperature (the warmer the temperature, the further north cod are to be found, and vice versa). With regard to the Barents Sea, Cury et al. published an article in 2008 which closely examined the link between oceanic conditions and the abundance of phytoplankton, zooplankton, capelin, herring and cod.
The links of interdependence within the ecosystem are also time-based. During the most sensitive phases of an alevin's life - for instance, its first few days - it needs to be able to feed upon one or several specific prey that are normally abundant at the time of reproduction. However, global warming frequently produces a time-lag between the plankton bloom and the moment of reproduction, thereby resulting in the latter's failure.
Finally, climate change seems to amplify the consequences of overfishing . In several ecosystems where upwelling occurs - accounting for 3% of the ocean's surface, but providing 30-40% of its productivity - global warming is thought to increase the waters' temperature-based stratification, to limit the upwelling of deep waters and to weaken the trade winds , all principal characteristics of these zones. Warmer and less "mixed", the surface waters would become less and less oxygenated as organic decomposition would become more and more concentrated. This natural mechanism would greatly favour the anoxia of those ecosystems devastated by overfishing, such as that of Benguela, where the disappearance of predators and pelagic fish allows for the development of invertebrates, jellyfish and gobies. Anoxia is also a very common phenomenon in the ocean depths because the phytoplankton are no longer fed upon and fall while decomposing. The lack of oxygen even forces lobsters to leave the water and invade the beaches of Namibia, where they consequently die of dehydration.
B. THE DIRECT IMPACT OF HUMAN ACTIVITIES AND POLLUTION
Pollution's impact on marine waters is poorly measured and it is difficult to determine its consequences on animal life.
Fishermen believe that they can directly measure the impact on their catches. They point out that while marine zones are less and less free, they are being subjected to an ever-growing number of activities that pollute or disturb the environment. They are more and more openly concerned regarding the outflows of rivers such as the Rhône, the Loire, the Seine and the Garonne. The PCB crisis gave voice to fishermen who previously were unable to make themselves heard in opposition to the industrial and, more generally, terrestrial interests. Fishermen are fearful that the entire "plume" at the mouth of France's main rivers may be polluted, thereby rendering fishing impossible.
This issue is of great importance for IFREMER ("French Research Institute for Sea Exploration"). In its 2007 activity report, of the 28 research projects or programmes under the heading "Monitoring, use and promotion of the coastal seas", 13 (or nearly half) were concerned with toxicity and pollution.
1. Plastics, macro- and micro-waste
Pollution in the form of plastics is one of the most readily visible examples of this phenomenon. Everyone has in mind the far from brilliant spectacle of beaches before their cleanup. Sailors often testify to the ever-growing amount of waste that they encounter during their voyages. The perfect example of this form of pollution at the world level is the "Great Pacific Garbage Patch" (see Curtis Ebbesmeyer), a zone in which the central gyre 7 ( * ) of the Pacific Ocean concentrates considerable quantities of waste. This area is said to be 1.25 times the size of France and to include more than 3 million tonnes of diverse plastics. While the area's microparticles of plastic, which are estimated to outweigh the zone's plankton by six to one, are continually disintegrating, they do not disappear.
2. 40% of the oceans' surface is greatly influenced by man
The issue of measuring man's global impact on the marine environment is the subject of numerous studies. A threshold was recently crossed by American researchers at the National Center for Ecological Analysis and Synthesis (NCEAS) under the direction of Benjamin Hapern of the University of California at Santa Barbara. They managed to draw up a special world map, published in the revue Science in February 2008 8 ( * ) , showing that more than 40% of the oceans' surface is very strongly affected by human activities . This map represented a real breakthrough, because up until then, measurements had existed only for localized impacts or the effects of only one or a few activities.
The researchers created this composite map in four steps. Firstly, they collected or created world maps covering all types of human activity having an impact on the marine environment, for a total of 17 activities, from fishing to climate change to pollution. They then estimated the ecological consequences of these activities and developed a method for quantifying the vulnerability of each ecosystem. The third step consisted in their combining the impact and vulnerability maps. Finally, they cross-checked the maps available on the state of the ecosystems with the results obtained concerning human activities and ecosystem vulnerabilities.
The authors felt that this map sounded an alarm for the state of the oceans, even though much of the damage remained hidden or was seen in an isolated manner. They admitted that they were astonished by the results, which were worse than they had imagined.
Indeed, large areas of the North Sea, the China Sea, the Mediterranean Sea and the eastern coast of the United States are extremely affected.
However, rather than constituting a hopeless observation, this map remains an ever-changing tool which will grow in precision with the improvement of the available data in a cooperative process involving the rest of the interested scientific community. Above all, this map represents a management and conservation tool to be used by government authorities in defining and optimizing protected marine zones and in developing an ecosystem-based system of management. Indeed, such a map can help authorities set priority zones and measures, by identifying not only the most- but also the least-damaged zones .
C. THE SCIENTIFIC CHALLENGE OF MANAGING HALIEUTIC RESOURCES
Fishermen often explain that fishing is similar to farming, even ploughing. The sea is less productive wherever fishing isn't pursued.
This assertion may come as a surprise, for fishing is a form of "gathering", but it does have a scientific basis. Indeed, fishing exploits the capacity of an animal population to regain its original biomass following its temporary reduction resulting from an additional mortality.
" When the abundance of a natural population is reduced by fishing, the population reacts to the removal of individuals by increased survival and growth rates and the recruitment of survivors who now enjoy greater space and food ," explains Jean-Paul Troadec, Jean Boncoeur and Jean Boucher in the 2003 report of the Académie des Sciences ("French Academy of Sciences").
Therefore, fishing can - to a certain extent, depending on each stock (species, environment, climatic conditions) - maintain a heightened level of productivity and give this impression of "farming". However, it nevertheless remains a form of gathering, with over-exploitation eventually leading to a decreased catch.
The two levers of this management are the fishing effort, which determines the "mortality by fishing" (not to be confused with "natural mortality"), and the distribution of this effort in accordance to age class (juveniles, spawners, etc.).
Scientists continue to be extremely sceptical regarding man's ability to actually increase an ecosystem's natural productivity in the long term by way of planning, because it would seem extremely difficult to really increase food production, even if one can encourage refuges or concentrations. In fact, it is the abundance of nutrient salts that determines the amount of phytoplankton, which in turn determines the amount of zooplankton, which in turn controls the amount of small pelagic fish and their predators . Ecosystems are thus controlled from the bottom up. This explains the natural fluctuations of herring in the North Sea or of sardines off the coast of Brittany. Winds play a decisive role in this food chain by mixing the deep ocean waters with the surface waters, as well as the marine currents.
Therefore, a natural productivity "ceiling" exists which applies as much to fishing as it does to shellfish farming , the capacities of any given body of water being limited.
Having explained this important principal, your rapporteur would now like to take a more detailed look at the principles upon which the management of halieutic stocks are based, for several differ significantly from their terrestrial counterparts and may therefore appear counterintuitive.
1. Is the objective of a Maximum Sustainable Yield (MSY) attainable?
The idea of managing marine resources and being able to maximize their exploitation has a scientific history. We have come a long way since Grotius stated in 1609 in his Mare Liberum that "Sea fishing is free, for it is impossible to exhaust marine resources" - as compared to the fishing of rivers, whose stocks can be rapidly exhausted. In this section, your rapporteur will refer to the work carried out by Philippe Cury and Yves Miserey.
It was only in the mid-19th century that scientists began studying the management of our halieutic resources.
Previously, it was believed that it would be possible to restock the seas, as was done for rivers by introducing a large number of alevins. Beginning in 1911, the French ichthyologist Louis Roule demonstrated the futility of attempting to repopulate the oceans to any extent comparable to natural levels. Nevertheless, such attempts would continue up until the First World War.
At the same time, the Norwegian researchers Axel Boeck and Ossian Sars began carrying out their first studies in the late 1850s on the Arctic cod fishery of the Lofoten archipelago. They managed to demonstrate the twofold process regulating the Arctic cod population, with the resource's natural variation on the one hand and the "overcapacity mechanism", which periodically resulted in the fishery's collapse, on the other .
Also at the same time, quantitative and statistical analysis methods were developed and widely accepted; these would eventually lead to the construction of a fishing theory which allowed for the scientific and therefore "certain" definition of a given stock's optimal, rational management. In many respects, the very idea of a maximum sustainable yield is therefore the product of the mid-19 th century's scientific rationalism.
One of the founding fathers of this movement was the English biologist Michael Graham . He based his findings on observations of the North Sea plaice fishery. In particular, he remarked that lower catches during the First World War had allowed the stock to recover. He therefore demonstrated that the amount of fish caught did not increase in step with the overall fishing effort; rather, an ever greater fishing effort could result in a decrease in profitability and overall tonnage. Graham concluded that regulation of the fishing effort was the key to fishery management . In addition, he observed that attention must be paid to age classes, with a very different number of fish able to account for the same catch weight. Therefore, he also demonstrated that fishing is capable of stimulating, to a certain extent, the productivity of a given stock . Graham's work greatly influenced the research of the 1930s and paved the way to a veritable scientific calculation of the ideal maximum catch.
In 1954, it was Schaefer who proposed a mathematical formula for calculating the catch that would allow a given stock to regain its initial equilibrium by increasing its natural growth and to establish a new exploitation equilibrium.
Schaefer was therefore the first to define this concept of the maximum catch that could be sustained by a given stock, resulting in the Total Allowable Catch (TAC) and the Maximum Sustainable Yield (MSY).
However, the productivity of a given stock is determined by three factors:
- Recruitment; in other words, the number of eggs produced, which is determined by the mass of spawners. The overfishing of spawners, especially among long-lived species with low reproductive rates, can rapidly result in the stock's decline and what is referred to as "recruitment overfishing". What is more, the most commonly fished species are or were very prolific species, such as cod, herring and sardines.
- The environment also plays a decisive role in the survival rate of the early stages: eggs, larvae and alevins. Many species are very fragile: should the water temperature rise or decline by a few degrees or the necessary prey prove scarce, the stock's effective recruitment may collapse. Most fish stocks are therefore subject to a high level of interannual variability, the effects of which are normally cushioned in a healthy population by the number of age classes. Therefore, due to unfavourable conditions, a stock can prove incapable of sustaining an increased mortality rate linked to fishing.
In addition, when considering the collapse of a given stock, it is often difficult to distinguish between the effects of overfishing and the effects of temporary environmental conditions. Frequently, both these factors are to blame.
- Finally and thirdly, the catch volume depends on the exploitation profile of the stock's age classes. It is generally accepted that sparing juveniles and allowing fish to reproduce at least once will eventually allow for an increase in captures. However, catch selectivity remains limited by its being almost always multispecific in character and by the levelling nature of a given selection method.
The concepts of TAC and MSY apply to a single species and, in theory, can only apply to monospecific fisheries. This constitutes a major weakness. However, at the time of the Schaefer model's formulation and in the midst of the world fisheries' expansion and the extension of the exclusive economic zones, this model was seen as the quantitative and scientific solution guaranteeing the most effective exploitation of marine resources. It also allowed for overfishing to be defined as an overstepping of this mathematical limit.
An additional consideration was supposed to be addressed with the appearance of the "structural models"; in other words, taking into consideration a population's structure, or its size and age. These models were first developed by Wicker who studied salmon and haddock and established a link between the number of spawners and the number of recruits. Then Beverton and Holt, carrying out studies on these same species, as well as on the plaice, succeeded beginning in 1957 to provoke management measures seeking to more scientifically regulate net-mesh sizes. These studies reinforced the idea that a scientific and quantitative management of catches would provide the necessary guaranties for a fishery's successful exploitation. At the time, this scientific approach also allowed for the blocking of all or almost all catch constraints, as long as the MSY was respected.
These management principles were officially and internationally adopted by the FAO in Rome in 1955 by a very close vote of 18 to 17, for behind the scientific theory, the freedom of access to fishing zones was at stake and this access had to remain unlimited. The United States made all of its weight felt to guarantee its continued access to such zones as Peru and Mexico.
Over the following years, fish catches would be managed according to these halieutic models of population dynamics, sidelining the studies which, from the very beginning, had allowed for the establishment of the twofold bio-economic process between fish and fishermen.
2. What is the maximum potential of the world's oceans?
In parallel to these efforts to manage fishing stock by stock, researchers have attempted to calculate the overall catch potential of the world's oceans. In most cases, these attempts have proved hazardous due to the climate at the time and insufficient data. In 1951, an estimation of 22 million tonnes was put forward (Thompson); later, in the early 1970s, the figure varied between 200 million and 2 billion tonnes! From 1978 to 1994, the estimations remained very large and optimistic, varying between 100 and 350 million tonnes. Today, and considering the evolution of catches over the past twenty years and the state of fish stocks, it seems most likely that future marine catches will vary between 80 and 100 million tonnes maximum .
Daniel Pauly used another approach to estimate the oceans' potential. He sought to determine the volume of the ocean's primary production appropriated by man via fishing. Early figures from the 1980s had led scientists to estimate man's impact as being equal or inferior to 2.2%, an extraordinarily low estimation when one considers that 35-40% of terrestrial primary production is used by man.
Daniel Pauly set out to reanalyze these same data, while integrating rejected catches and, above all, taking into consideration the trophic level of catches, aware that the yield is some 10% from one predator to the next (10 kg of prey for 1 kg of predator). His calculations resulted in a new estimation of 8%, four times greater than the first, though still far removed from the terrestrial figures.
These data were distorted by the fact that the ocean is not uniformly productive; by limiting the catches to the "fertile" zones, the actual rate of appropriation varies between 24.2% and 35.3%, depending on the zone. These results clearly indicated that fishing had undoubtedly reached its maximum sustainable potential.
3. Collapses, irreversible changes and questioning traditional halieutics
Generally speaking, it has been the stock collapses that have occurred since the 1950s (the California sardine, the North Sea herring and, above all, the Canadian cod) that have led to a questioning of monospecific and quantitative halieutics.
It has since been shown that stocks can collapse without forewarning (Mullon et al., 2005). Since 1950, a quarter of the 1,519 species studied have collapsed, a fifth of which did so brutally following a plateau of production . This is explained by the fact that there exists a "spawner threshold" below which reproduction is no longer assured; however and at the same time, the fishing effort may continue to grow - if only due to technological progress - allowing for a stability of catches and masking the evolution under way. Therefore, catch stability is not an indicator of a healthy stock or effective management. Much more detailed data are required.
In addition, once the stock has collapsed, it is not enough to stop fishing to allow the population to recover. In a certain number of cases, it entails a change of regime , with a new species becoming dominate within the ecosystem and preventing the ousted species from recovering its previous place due to the predator-prey relationship that is essentially dependent upon size in the marine food chain. The change is therefore irreversible. For example, it has been demonstrated that the collapse of the North Sea herring stock resulted in a lack of food for the capelin and therefore for the cod which eat herring and capelan; this in turn led to cannibalism within the cod population, with adults eating juveniles, thereby greatly limiting the stock's growth.
In a much more dramatic manner, in the North Benguela upwelling 9 ( * ) off the coast of Namibia , the over-exploitation of sardines, anchovies and hake has also led to this type of evolution. In the same zone in which 1.5 million tonnes of sardines were fished in the 1960s, the last scientific evaluation programme in 2007 was only able to capture two sardines in the entire ecosystem. The disappearance of entire trophic levels favours the lower levels (sponges, macro-algae, jellyfish, bacteria, sea urchins), which become dominate within the ecosystem.
Unfortunately, there are many such zones, some of which are linked to telluric pollution such as the anoxic zone at the mouth of the Mississippi Delta. 60 such zones have been recorded in the world (Robert Diaz).
They are to be explained by the fact that the ecosystem's primary production is no longer recycled, falls to the ocean floor and decomposes, thereby monopolizing the dissolved oxygen to this single end.
Chesapeake Bay and the Black Sea are other well known examples. Other systems are not as greatly damaged, but give worrying signs, such as the waters off the coasts of Morocco, Mauritania and Senegal, whose main resource is now the octopus, an animal entirely absent only twenty years ago.
The proliferation of jellyfish in the Mediterranean or the dramatically small size and low weight of the fish caught in the Bay of Biscay (23 cm) and the North Sea (fish weighing over 4 kg have decreased by 98%) are warning signals that should catch our attention.
In addition to this risk of a stock collapsing without forewarning, one must also consider a new complexity: numerous species of fish change sex . Common sea bream and white sea bream are "protandrous functional hermaphrodites"; meaning, they change sex as they age. When young, the fish are male and become female. The opposite also exists: "protogynous functional hermaphroditism"; this is the case with the grouper, the salema and the anthias. In other species, such as the Mediterranean porgy, it is the proportion of males and females which varies according to age. Finally, water temperature determines the sex of certain other species, such as sea bass; this could have serious consequences as a result of global warming.
It is therefore essential to consider this phenomenon of "sexual flexibility" when managing fisheries, in particular when selectivity is based primarily upon size. It could therefore become necessary to favour selection methods that allow the largest fish to escape, so as not to provoke too great an imbalance between the sexes.
It is probable that the West African grouper is a victim of this situation. Overfished, it was the largest specimens which were the first to be caught. The wild population could now lack enough males to reproduce.
What is more, the exploitation's economic aspect plays an important role. Fishing does not necessarily come to a stop due to a lack of fish. As a fish becomes more and more rare, its price rises, as does its demand as a luxury product; at a certain point, there may no longer exist an economic check with which to protect the species from becoming extinct. Indeed, this is the case with certain large terrestrial mammals. Such a situation can also be observed with regard to sturgeons and certain crustaceans.
In addition, the listing of common halieutic species on the red list of endangered species has become a topical subject. This list already includes the Altantic cod, the North Sea haddock, the Antarctic bluefin tuna and some one hundred other species. The Mediterranean bluefin tuna could soon be added.
* 1 The title of the book by Philippe Cury and Yves Miserey, Une mer sans poissons ("A Sea Without Fish"), Paris, Calman-Lévy, 2008, 283 pages.
* 2 Fayard, Paris, 2006, 256 pages.
* 3 Cited by Paul Molga, Les Echos, Wednesday, 6 February 2008, p.13.
* 4 Science, 320, 336, 2008.
* 5 La Recherche, no. 420, June 2008, pp. 16-17.
* 6 Vol. 35, L03618, 2008.
* 7 Circular current.
* 8 14 February 2008, 319, 948-952.
* 9 Coastal oceanic zone in which nutrient salts and cold water are pushed to the surface by marine currents, winds and the particular morphology of the ocean floor.