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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This volume provides various examples and dimensions, chemical, biological, climatic, or related to extreme (hazards). It describes, by reciprocity, the vulnerability of ecosystems, resources, heritage, human health and, consequently, economic and social sectors. it considers climate scenarios and socio-economic status indicators research, design strategies and patterns of adaptation, development of innovative monitoring systems, analysis of perceptions of major hazards and valuation of ecosystem services.
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Seitenzahl: 329
Veröffentlichungsjahr: 2014
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Contents
Foreword
1 Ocean, Biodiversity and Resources
1.1. The history of life in the oceans
1.2. Specifics of marine biodiversity
1.3. Renewable living resources
1.4. Ocean and public health
1.5. Research of molecules of interest of marine origin
1.6. Research in marine models (regarding their originality and specificity)
1.7. Conclusion
1.8. Bibliography
2 Pelagic Marine Ecosystems and Biogeochemical Cycles
2.1. Introduction
2.2. Marine pelagic ecosystems: from viruses to whales
2.3. Pelagic ecosystems and biogeochemical cycles: inseparable
2.4. The ocean in the rescue of the planet: carbon pumping and sequestration
2.5. Biogeochemical equilibria, ecosystems and human societies: danger!
2.6. Bibliography
3 Indicators
3.1. Introduction
3.2. Approach
3.3. Selecting indicators
3.4. From indicators to ecosystem assessment
3.5. Giving advice
3.6. Indicators in practice
3.7. A summary by way of conclusion
3.8. Acknowledgments
3.9. Bibliography
4 The Impact of Global Change on the Dynamics of Marine Living Resources
4.1. Fisheries, aquaculture and food supply
4.2. From exploited populations ecology knowledge to fisheries management
4.3. From concepts to reality: management and governance
4.4. From EAF to the systemic approach: working toward a better regulation for the usages of marine biodiversity
4.5. Appendix
4.6. Bibliography
List of Authors
Index
First published 2014 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUK
www.iste.co.uk
John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USA
www.wiley.com
© ISTE Ltd 2014The rights of André Monaco and Patrick Prouzet to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.
Library of Congress Control Number: 2014950499
British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-84821-703-4
Foreword
We have been asked by ISTE to stimulate work in the area of the environment. Therefore, we are proud to present the “Seas and Oceans” set of books, edited by André Monaco and Patrick Prouzet.
Both the content and the organization of this collection have largely been inspired by the reflection, initiatives and prospective works of a wide variety of national, European and international organizations in the field of the environment.
The “oceanographic” community, in France and internationally – which is recognized for the academic quality of the work it produces, and is determined that its research should be founded on a solid effort in the area of training and knowledge dissemination – was quick to respond to our call, and now offers this set of books, compiled under the skilled supervision of the two editing authors.
Within this community, there is a consensus about the need to promote an interdisciplinary “science of systems” – specifically in reference to the Earth’s own “system” – in an all-encompassing approach, with the aim of providing answers about the planet’s state, the way it works and the threats it faces, before going on to construct scenarios and lay down the elementary foundations needed for longterm, sustainable environment management, and for societies to adapt as required. This approach facilitates the shift of attention from this fundamental science of systems (based on the analysis of the processes at play, and the way in which they interact at all levels and between all the constituent parts making up the global system) to a “public” type of science, which is finalizable and participative, open to decision-makers, managers and all those who are interested in the future of our planet.
In this community, terms such as “vulnerability”, “adaptation” and “sustainability” are commonly employed. We speak of various concepts, approaches or technologies, such as the value of ecosystems, heritage, “green” technologies, “blue” chemistry and renewable energies. Another foray into the field of civilian science lies in the adaptation of research to scales which are compatible with the societal, economic and legal issues, from global to regional to local.
All these aspects contribute to an in-depth understanding of the concept of an ecosystemic approach, the aim of which is the sustainable usage of natural resources, without affecting the quality, the structure or the function of the ecosystems involved. This concept is akin to the “socio-ecosystem approach” as defined by the Millennium Assessment (http://millenniumassessment.org).
In this context, where the complexity of natural systems is compounded with the complexity of societies, it has been difficult (if only because of how specialized the experts are in fairly reduced fields) to take into account the whole of the terrestrial system. Hence, in this editorial domain, the works in the “Seas and Oceans” set are limited to fluid envelopes and their interfaces. In that context, “sea” must be understood in the generic sense, as a general definition of bodies of salt water, as an environment. This includes epicontinental seas, semi-enclosed seas, enclosed seas, or coastal lakes, all of which are home to significant biodiversity and are highly susceptible to environmental impacts. “Ocean”, on the other hand, denotes the environmental system, which has a crucial impact on the physical and biological operation of the terrestrial system – particularly in terms of climate regulation, but also in terms of the enormous reservoir of resources they constitute, covering 71% of the planet’s surface, with a volume of 1,370 million km3 of water.
This set of books covers all of these areas, examined from various aspects by specialists in the field: biological, physical or chemical function, biodiversity, vulnerability to climatic impacts, various uses, etc. The systemic approach and the emphasis placed on the available resources will guide readers to aspects of value-creation, governance and public policy. The long-term observation techniques used, new techniques and modeling are also taken into account; they are indispensable tools for the understanding of the dynamics and the integral functioning of the systems.
Finally, treatises will be included which are devoted to methodological or technical aspects.
The project thus conceived has been well received by numerous scientists renowned for their expertise. They belong to a wide variety of French national and international organizations, focusing on the environment.
These experts deserve our heartfelt thanks for committing to this effort in terms of putting their knowledge across and making it accessible, thus providing current students with the fundaments of knowledge which will help open the door to the broad range of careers that the area of the environment holds. These books are also addressed to a wider audience, including local or national governors, players in the decision-making authorities, or indeed “ordinary” citizens looking to be informed by the most authoritative sources.
Our warmest thanks go to André Monaco and Patrick Prouzet for their devotion and perseverance in service of the success of this enterprise.
Finally, we must thank the CNRS and Ifremer for the interest they have shown in this collection and for their financial aid, and we are very grateful to the numerous universities and other organizations which, through their researchers and engineers, have made the results of their reflections and activities available to this instructional corpus.
André MARIOTTIProfessor Emeritus at University Pierre and Marie CurieHonorary Member of the Institut Universitaire de FranceFrance
Jean-Charles POMEROLProfessor Emeritus at University Pierre and Marie CurieFrance
1
Ocean, Biodiversity and Resources
1.1. The history of life in the oceans
The Earth was formed 4,600 million years ago. From ancestral geodiversity originating from prebiotic chemistry, which gave rise to the set of chain reactions that produced the first structured sugar, nitrogen base and amino-acid molecules, “life” appeared in oceans, fairly quickly after the initial cooling and condensation of water, over 3,800 million years ago.
Duve [DUV 96], 1974 Nobel Prize Laureate, said, in Dust of life in 1996, that Earth was so ideally positioned with respect to the Sun that it would not be possible for life not to appear (i.e. it was bound to), while J. Monod referred to it as an improbable occurrence. The oldest known sedimentary rocks (Akilia Island, in South Greenland) containing carbon of biological origin date back 3,850 million years. We must imagine very primitive life at the start, based on a world of ribonucleicacid (RNA) and protocells [MAU 03]. Current deposits of stromatolite (rocks that precipitate bicarbonate), with very rich deposits in Australia, are very precious since, in their silicified parts, they contain the most ancient known fossils of microorganisms: cyanobacteria. These began their conquest of the oceans around 3,400–3,200 million years ago, at the time without any atmospheric oxygen. In the presence of water, photosynthesis produces oxygen and sugars from light and carbon dioxide (CO2) due to specific pigments in the cells; this process began to take place on Earth around 3,500 million years ago. Oxygen started to diffuse beyond the confines of the aquatic environment around 3,200 million years ago; the current composition of the atmosphere, with its 21% of oxygen, dates back at around 100 million years, in the Cretaceous Era.
In this ancestral ocean, events occurred that were of critical importance both for the living world in general and for biodiversity:
Another exceptional occurrence took place in this ancestral ocean: the appearance of sexuality, first with prokaryotes, and later also with eukaryotes, which would prove to be essential for the explosion of biodiversity. Sexual reproduction allows for genetic mixing, which creates originality and unprecedented diversity: all individuals are different. A population endowed with sexuality evolves much more quickly. Furthermore, the prevalence of sexuality facilitates the development of an “arms race” between parasites and their hosts (coevolution and molecular dialogue [COM 01]), as genetic mixing ultimately leads to quicker “neutralization” of the parasite, and sexual selection that is clearly different to natural selection [DIM 05].
The exit of organized metazoan life from the oceans took place after the Cambrian explosion (570 million years ago), where the first plant life-forms (first vascular plants in the late Silurian, around 415 million years ago, with moss existing long before that) and terrestrial animal life-forms (arthropods and vertebrates, among others) would leave traces on the continents (myriapods, scorpions, later lungfish, rhipidistia and Ichthyostega, around 440 million years ago). Numerous new adaptations were developed, both by plants and animals; the transit to terrestrial life and air-breathing represent an exceptional occurrence in the history of life. The differences are fundamentally between aquatic and terrestrial animals. The former extract their oxygen from water through diffusion to the heart of the organism for small species, or through gills for larger ones. A volume of seawater at equilibrium with the air contains around 30 times less oxygen than the same volume of air. Anisosmotic aquatic breathers (whose internal environment is different to the surrounding water – e.g. fish) cannot develop too large an exchange surface (gills) due to the dangers inherent to the physical consequences of osmotic “flows” (water and electrolytes), with the animal losing water to the sea, or being “flooded” by river water. In fact, a fish is constantly subject to a difficult compromise, between developing a maximum gill surface, to capture the oxygen in an oxygen-poor and very changeable environment, and a minimum surface to help prevent serious water–mineral imbalances. Aquatic animals excrete ammonia and, for the vast majority, do not thermoregulate. By contrast, terrestrial animals must endure ultra violet (UV) rays, dehydration, a very different experience of gravity (consequently, requiring a much heavier and resistive skeleton and muscle mass), and must use excretion products that are not highly toxic or are non-toxic (such as, uric acid or urea). Much later, in the Triassic period, around 210 million years ago, after the third great species extinction crisis, the premises of thermoregulation were developed, and used to maximum efficiency first by large dinosaurs, and then mostly by birds and mammals. A very good example of the return to the ocean is the case of cetaceans, which began this reacclimatization to marine life based on the primitive terrestrial forms of artiodactyls (for example, hippopotami) similar to Diacodexis, and then amphibian forms (like the Pakicetus or Ambulocetus) around 55–50 million years ago, whose current giant forms (the largest animals to have populated the planet since the origins of life, which humans have been uncaringly massacring for 160 years) are very recent. Today, 12 phyla are exclusively marine animals and have never left the ocean (echinoderms, brachiopods, chaetnognaths, etc. – see Table 1.1). However, only two exclusively terrestrial groups (not phyla) exist: myriapods and amphibians. Additionally, the seas contain vast quantities of biomass: the bacteria in the subsurface layer of the ocean alone represent 10% of all carbonated biomass on the planet [PAR 94]. The marine environment has, therefore, played a decisive role in the history of life, and today the ocean continues to play a crucial role in the evolution of life and climate [BOE 08].
Today, we are searching for traces of “extraterrestrial” life, by concentrating efforts on DNA, amino-acids, Adenosine triphosphate (ATP), etc., without forgetting that the key molecule of life is water. The make-up of every living being contains water – ranging from a few percent, in the case of the “driest” organisms (e.g. plant seeds), to over 95%, for certain aquatic species (algae, jellyfish, ascidia, among others). The human body itself is made of two thirds of water; a human baby at birth has 75% of water and our brain has more than 80%. Water is life [BOE 12]: for example, take the borders of a Chilean desert which, every 10–12 years when it rains, becomes covered with flowers (along with vast numbers of insects) in the space of a few days, lasting a few weeks, and then “returns” to years of extreme aridity. This is natural; however, humans can also trigger explosions of life by irrigating the desert.
The departure from water was, therefore, a truly decisive event in the history of life. The ocean has been salty (essentially with sodium chloride) for a very long time, and today we are able to understand this stability in its salinity: the billions of tons of cations (calcium, potassium, magnesium, sodium, etc.) brought to the sea by the rivers since they began flowing, are compensated for: in the case of calcium, by the trapping of marine sediments and the formation of limestone; for potassium by the absorption of clay (see Chapter 4 in [MON 14a] and Chapter 2. Magnesium and sodium are retained in the oceanic ridges (serpentinization and clay-formation from pyroxenes and olivines). Serpentinization corresponds to the hydration of minerals, and alteration into clay corresponds to the deterioration into small grains of less than 2 μ in diameter. For anions, bicarbonates are constantly mixing with the atmosphere and biosphere, and for chlorides, which do not enter into any major biogeochemical cycles, we currently believe that chlorine was one of the original volatile elements that was dissolved in seawater initially and remained there (not much is carried by rivers today). This current salinity, of around 35 psu (internationally recognized “practical salinity unit”, corresponding to 35 g of sodium chloride per liter) causes osmolarity (meaning “osmotic pressure”) of 1,050 milliosmoles per liter (mOsm.l−1).
Marine life has always had to cope with this, and has developed a universal strategy of intercellular isosmotic regulation for which the vast majority (of animals only) of invertebrates and certain vertebrates have the same osmotic pressure (internal environment and cells) as that of seawater. Another strategy, which has arisen in certain crustaceans, referred to as extracellular anisosmotic regulation, has allowed for great migration capabilities and the ability to change environments, by maintaining the osmotic pressure of cells and body fluids within a very small range (between 300 and 400 mOsm.l−1; humans are at 302); regardless of the external salinity. In fact, in this latter case, we can “die of dehydration” in seawater; the presence of salts causing outakes of water from the organism to the external environment through exchange surfaces in close contact (blood–water) with salt water, such as the epithelium of the mouth and gills (with seawater salts migrating in the opposite direction). Marine osmoregulators (for example, boned fish) have had to establish strategies for the constant intake of seawater and the evacuation of salts through the gill, with the kidney proving to be incapable of fulfilling this function on its own. One of the main problems posed by terrestrial life is the conservation of water and the struggle against dehydration [BOE 12]. The role of the kidney is, therefore, essential: think of the small kangaroo rat from the desert, which never has access to drinking water and produces urine that is nine times more salty than seawater. For its part, “terrestrial” biodiversity would develop later on, after the establishment of specific mechanisms, and took off massively in the Carboniferous Era, from 345 million years BC onward.
We will, therefore, take inspiration from certain aspects related to life in the ocean: first its age and its often much simpler organization, and second its productivity and specific diversity:
1.2. Specifics of marine biodiversity
Marine biodiversity is a very special case [BOE 11]. The recognized diversity of species in the oceans accounts for no more than 13% of the set of living species currently known: i.e. less than 250,000. There may be two reasons for this. The first is that our knowledge – especially of deepwater areas and microorganisms, bacteria and microalgae – is still only very incomplete (so we considerably underestimate the biodiversity of the oceans). New methods, such as coupling between flow cytometry (a technique that entails launching particles, molecules and cells at high speeds through a laser beam in order to characterize them) and molecular probes (which reveal an organism with specific features), are currently discovering a totally unforeseen, extraordinary level of biodiversity. “Sequencing the ocean” (C. Venter, sequencing all the DNA in a given volume of filtered seawater) moves in the same direction; the data obtained appear, for the most part, to be revelations. The recent round-the-world expedition Tara Océans has also produced exceptional data. For all prokaryotes and very small eukaryotes, recent molecular approaches (sequencing of 16S and 18S ribosomal RNA, among others) produce astonishing results daily. Furthermore, and this is the second reason, it is also obvious that marine ecosystems and the way of life in a continuous environment (by the dispersion of gametes and larval stages) of the species that populate it, are less predisposed to strict endemism (the notion of living exclusively here and nowhere else) than in terrestrial habitats. There are many more barriers and segregations favorable for speciation (the evolutionary process by which new living species arise) on land than in the sea. This leads to significant differences in terms of specific diversity; marine ecological niches do not achieve the richness of terrestrial ones, which are much more fragmented and are more favorable to new species. The stability of the open ocean in deep waters, over at least the past 100 million years, is also extraordinary: in terms of pH, osmotic pressure and salinity, temperature, hydrostatic pressure linked to depth, dissolved gas content, etc. The closer we are to the coast, the more this fluctuates. Human activity is changing this; we will revisit this point later on. This stability is less prone to give rise to new species. Consequently, marine biomasses can be considerable, and the performance of phytoplankton alone, with its capacity for self-regeneration, accounts for over 50% of the planet’s productivity.
Table 1.1. Exclusively marine phyla (according to [BOE 11])
This table is simply indicative of exclusively marine groups. How do we then chose them? Cephalochordata and tunicates are sub-phyla of Chordata (which have continental taxons), the Kinorhynca, Priapulida and Loricifera have been grouped within the Cephalorhyncha with the Nematomorpha, which are terrestrial; Xenoturbellida, Cycliophora and Mesozoa can be considered as valid phyla.
There are five to seven more terrestrial taxons today, compared to oceans, which is worthy of inquiry since initially life was exclusively marine, before the various great departures from the oceans, at different locations in different forms, 440 million years ago, for “developed” metazoans. The great Permian-Trias extinction played a primordial role with 96% of the extinction of species both marine and continental around 252 million years BC. The explosion of flower plant species, of insects and many other groups on Earth, around 130–110 million years ago, was decisive after the initial radiations (explosion in the number of species deriving from a single ancestral one) starting from the Carboniferous period. The coevolution between plants and pollinators, and the appearance of an infinite number of new niches, have often been proposed to explain the acceleration of speciation in continental environments of this era [BOE 11, BOY 10]. It is also evident that dispersion phenomena of reproductive products and larvae in the oceans played an important role in the distribution of current species and biogeography. Endemism is notably considerably more limited in the ocean, the stability in deep water and the continuity of this gigantic environment explaining this. If it is not rare to find living species over a few km2 on land, then we do not know of any examples of such confined species in the sea. The large variety of methods of reproduction in the sea also draws from dispersion phenomena in water bodies, with males and females not constrained to being in close proximity. Thus, do connectivity and the much weaker variations in environmental factors create the great stability in the ocean at large and the particularly specific characteristics of the biodiversity that it houses? Coastal systems, intermediaries with strong land-related influences, are subject to much greater variations.
Finally, we must not forget that biodiversity is much more than just specific diversity, which includes both species and their relative abundance. The meaning of the word “biodiversity” has been interpreted in many ways but generally expresses the “genetic information which contains each elementary unit of diversity, be it an individual, a species or a population”. This determines its history, past, present and future. Even then, this history is determined by processes that are also components of biodiversity. In fact, today we group different approaches under this term together:
1.3. Renewable living resources
Humans have been fishing since ancient times, certainly tens of thousands of years. As soon as they reached shores, they began to collect shells, algae, etc. As in agriculture and continental environments, humans have been farming certain marine species on the coasts for at least 4,000 years (Egypt, China, etc.). The use of renewable living resources being very well outlined elsewhere in this work and in others in the collection “Seas and Oceans”, I will limit myself to only a few generalized remarks here.
The latest statistics available from the Food and Agriculture Administration (FAO) in 2012, for the year 2011, give values of 78.9 million tons (Mt) for maritime fishing, 11.5 Mt for continental fishing, 19 Mt for algae (with only one for fishing) and 63.6 Mt for aquaculture (of which 19.3 Mt are for the sea), thus a total, of all the groups and aquatic environments combined, of around 173 Mt (see also Chapter 4.
1.3.1. Fisheries
Until the 1950s (apart from some very particular stocks already, herring from the North Sea and especially whales, etc.), we did not really record any tax-related overexploitation of fish stocks in the world. This was all accelerated after the end of the Second World War and the establishment of the intensive practice of trawling and the big ocean seine or with huge drift-nets. The question that has already been posed, “will fishing disappear, due to a lack of fish?” [CUR 12, CUR 13]. The collapse of the Newfoundland cod stock at the beginning of the 1990s after 500 years of “harmony” between harsh, but not excessively destructive, fishing across all of the countries bordering the North Atlantic (see Pêcheurs d’Islande by Pierre Loti) and the maintaining of the stock has been a symbolic example of “modern overfishing”. Today, the FAO tells us that three quarters of the world’s fish stocks are fully exploited or overexploited. In a 2006 paper, Worm et al. [WOR 06] had even announced the “end of fish” before the end of the half century.
From around 30 million tons of world marine products (including algae) in 1950, this statistic has changed to 80–90 Mt in the 1990s and has practically remained unchanged since (bar certain fluctuations in industrial fishing, during the El Niño years) despite increasingly sophisticated (and formidably efficient) methods of animal detection and fishing techniques. In fact, fishing activity forms a strange type of exploitation that is still active, and which dates back to prehistory, in a world of finite resources. Of course, living marine resources are by definition renewable, however, the recent crossings of exploitation “thresholds” have shifted certain stocks toward an overtaking of the limit of “renewability”, with “natural” recruitment no longer being sufficient. As long as a certain threshold is not crossed, we can always attempt, with adapted and firmly controlled measures, to restore the resource, with this holding true particularly when it comes to fishing. However, the pressure of fishing activity, always being the largest, oldest and most interesting for the market, has not ceased to increase and we can clearly see this by examining today’s landings: increasingly smaller fish, in increasingly smaller quantities. Species have reacted over a short amount of time, of less than 30 years, by adapting and allowing younger, smaller individuals to reproduce. However, in the context of severe climate change in the ocean, everything is made more difficult: less food, increasing salinity, temperature and acidity, new hypoxia zones, the introduction of new species, the mass destruction of coastal ecosystems, pollution, etc., this is beginning to have a major impact. Also, the diversion of coastal fisheries toward deep waters is not reassuring: a lack of knowledge, long-lived, scarce species, with late sexual maturity, essentially all that must rightly not be fished. It is not the same parties that exploit coastal and deep water zones. We must remember, however, that currently this is only being practiced by a minority and that more than 80% of the fishing fleet is made up of small fishing boats (Figure 1.1).
Figure 1.1. The small-scale fishery units of the Iquique port in northern Chile, exploit horse mackerel, sardines, mackerels and anchovies, and sometimes amberjacks and swordfish
The main problem remains the more global approach of “natural expenditures” in particular in the most productive zones situated at the interface of continents and oceans. This is, therefore, clearly a question of ecosystem-based fishing approaches. Another problem corresponds to “industrial” fishing (for making fish flour) which, using large ocean seiners, captures millions of tons (in fact, a quarter of the world’s resources) of open-sea fish of which the flesh is evaporated in the deserts on the coast of Chile or Peru in order to be transformed into oils or flours for world livestock farming (see also Chapter 2 in [MON 14b]).
Regarding marine living resources, and to make stocks as long-lasting as possible, the access to these resources must be legislated and limited. Different methods exist and are being tested, however, political incentives and dialogues with anglers have remained primitive. Open-sea resources are clearly starting to become very attractive.
Deep-sea fishing must, therefore, be rethought. If we want to ensure a long-lasting future for this activity, new exploitation methods must inevitably be discovered, being more economical in fossil fuels, respectful of the resources and biodiversity, and most notably better adapted to the regenerative capabilities of stocks. The approach must be consistent [CUR 12] and better integrated with other human ocean activities. A question, therefore, arises: why not emulate the continental environment, and massively develop marine farming?
1.3.2. Aquaculture
Contrary to popular belief, aquaculture is an ancient activity that dates back to Egypt and China at least 4,000 years ago. Aquaculture is in fact “water farming”, be it plants or animals. It can act as a strong support for fishing activities by, for example, helping to release young specimens of different species back into the sea or other bodies or streams of water, thus enabling the capture of the resulting adults. This is what has been communally referred to as sea-ranching, a very extensive aquaculture system. This can also be intensive and consist of farming animals in enclosed conditions (floating cages, reservoirs, bodies of water, etc): the animals are, therefore, in high density and are fed by the fish farmer. Intermediary systems also exist – e.g. oyster farming on beaches which, while they self-propagate within that environment, are nevertheless present in a much higher density than in a natural environment; carp in ponds, where numbers are not always fed. There is also production aquaculture, where we produce the animal’s meat using primary production (oysters, etc.) and transformation aquaculture, where we “transform” an animal protein into another animal protein for a more economically valuable species (carnivores, salmon, turbot, tuna, etc.). Today, the species of interest for aquaculture essentially consist of molluscs (bivalves, as in oysters, mussels, scallops, clams, etc. and gastropods such as periwinkles or abalones (Figure 1.2)), prawns (notably those in the Penaeidae family, or “gambas”) and varied freshwater, brackish and seawater fish (carp, eels, sheatfish, trout, tilapias, sturgeons in freshwater, milkfish, serioles, wolves, dorados, flatfish, salmon, tuna, etc.).
Even though we only consume a few species from terrestrial environments (cow, pork, mutton, chicken, guinea fowl, goose, etc.), we consume many more aquatic species (at least a few dozen “routinely”).
Figure 1.2. Production of juvenile abalones in a hatchery in Chile
Aquaculture, very comparable in its identity to agriculture and by representing a form, is nonetheless very different on some fundamental points:
When we observe production statistics, when we have already seen that fishing has been in complete stagnation over the last 20 years, or even in decline (regardless we must by all means fish less in the future), aquaculture is in constant growth, which is an interesting fact and is interesting to note in the works related to “large-scale agriculture”.
Table 1.2. World productions in aquaculture (data from [FAO 12]), in millions of tons
Today, aquaculture, for all aquatic environments, greatly surpasses fishing in value (100 million euros) and is matching it in terms of produced biomass. It is in freshwater that production has greatly increased, however, efforts in saltwater are also progressing. Aquaculture is mostly predominant in Asia, and China produces two-third of global resources on its own. This fact is not a coincidence; Asian populations have been integrating these “fish farms” into their way of life for a long time.
With the idea, which is effectively very logical, being to limit samples from nature through fishing and to “replace” missing aquatic proteins (especially in the context of ever increasing demand, for demographic reasons and also in the interest of “healthy produce”) with aquaculture, the implementation is not that simple. Aquaculture is clearly a massive success, however, it must establish itself as a longer lasting process, in todays’ highly changing and sometimes even unpredictable environment: climate changes, the rise of the sea level, temperature, salinity, acidity, increasing hypoxia in the world’s waters, loss of diversity, arrival of “exotic species”, wild and varying access to the coast spurring heavy conflicts between involved species, pollution (including that produced by aquaculture), etc.
Moreover, outside of its role in the production of proteins, aquaculture can form an activity that complements fishing, since these two activities are not systematically incompatible with each other, as opposed to how it is often portrayed in France. We must simply observe what is happening in Japan or on the west coast of North America, for example. Through aquaculture, and due to modern enclosure techniques, we can produce a system confined to larvae or even better, juveniles, and then release them into the natural environment that heavily contributes to the maintenance or development of the resource. This is obvious for Pacific salmon for which the juveniles or smolts are released in the hundreds of millions into the north Pacific (sea-ranching) and which, once the adult stage is reached, are captured by fisheries on the return migration route. Thus, 70–90% of coho salmon caught by Canadian and American fishermen are born in fish hatcheries. Examples of restocking or sea-ranching are present not only with salmonids, but also with cod, sturgeon, scallops, prawns, etc.
The inverse system also exists (capture-based aquaculture), and one of the best examples is the farming of seriole, a silver fish, in Japan [NAK 08]. Juveniles are caught at sea in spring by fishermen and put into farms in large floating cages. They are then, after having been fed with fresh or frozen fish meat, gathered after 6–18 months and put on the Japanese market. This is the most widely produced species of “strictly marine fish” today in the world (160,000 tons in 2010). Scallops are put into farms in Chile from fished juveniles and supply the scallop farms that produce excellent produce for exporting. Wild animals can also be well “enclosed” by fishers into sea or land structures and be preserved living, fed or not, in order to be put on the market when the prices are at their highest (for example, the large bluefin tuna in Australia, Spain, Japan and Croatia).
Although world aquaculture is an extraordinary success and represents a fabulous source of protein for the future (over one year: +10% for plants, +8% for animal produce), at least three unavoidable questions must be asked.
1.3.2.1. The farming of carnivorous species
One of the essential questions has to do with the future of farming of carnivorous species, which require animal proteins for their diet. Can we continue to fish a quarter of all halieutic resources of the planet, directly useable by humans, in order to provide animal protein to farms (both aquatic and terrestrial, which the latter can do without)? And can we continue doing this, if it is possible? Answering these questions will require constant contact between private groups and public organizations. Certain works show the deleterious effect of current practices [NAY 00] not only by ocean fisheries, but also by aquaculture itself. The best obtained food transformation rates hover around 3.5 kg of caught fish to produce a gain of 1 kg of farmed carnivorous animal biomass when they are fed with artificial food (50% fish flour in the food, sometimes 70%) and of more than 5–6 kg (up to 12 for tuna) when they are fed with fresh fish. This has for a long time highlighted the different attempts that have been developed to both reduce fishing efforts devoted to the production of fish flour and also reduce the proportion of fish flour used in fish foods. Efforts have been made with trout and certain marine fish to replace animal proteins in the diet with others, of plant-based origin: soy, peas, lupin, rapeseed with certain zoophagous species (for example, trout) having been farmed without any animal-based foods. The prospects probably exist, however, certain species cannot be produced without the use of animal-based flour or oils. We have also progressively increased the quantity of lipids in food in order to reduce the impact of phosphorus and nitrogen on the environment.
It is clear that the farming of algae and mollusks, as well as that of omnivorous fish, is much more promising. These fish are much less “appreciated” in the market, however, they prove to be extraordinary transformers of the primary biomass and help to feed hundreds of millions of humans in South-East Asia, China, Africa or South America. They are the ones that explain the progression of the global production numbers. Often, in these regions, the only accessible animal protein is of “aquatic” origin.
Aquaculture can also provide meat of excellent quality at high prices for “high-end” markets in rich countries (the Japanese hirame, a flat fish or turbot, for example, sturgeon caviar and imperial prawn meat) as well as “cheaper” meat (even if it is of as good quality on a biochemical level and in its composition) of tilapia, catfish or mullet to feed poorer populations. Asian pangasia and catfish have thus flooded the European market. Carp and tilapia can be farmed in “medium” quality water, loaded with ammonia and poor in oxygen. The returns (rate of ingested food/weight gain of the farmed animal) are sometimes extraordinary, such as with tilapia in India. Mollusks are also very interesting since they are very “profitable”, however, they return little meat (the shell weighs a lot) and often reach prices that are too high for the majority of populations. Mussels are particularly interesting, however, they are very sensitive to the water quality and are not exempt from dangers to the consumer if a certain minimum of precautions are not taken.
