Harvesting the Ocean - Encyclopedia of Life … Chapters/C09/E2-27-01-06.pdfUNESCO - EOLSS SAMPLE CHAPTER MARINE ECOLOGY – Harvesting the Ocean - Y. Olsen, A. Endal the world’s

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MARINE ECOLOGY – Harvesting the Ocean - Y. Olsen, A. Endal

HARVESTING THE OCEAN Y. Olsen Trondheim Biological Station, Norwegian University of Science and Technology, Trondheim, Norway A. Endal Department of Marine Engineering, Norwegian University of Science and Technology, Trondheim, Norway Keywords: Humans’ marine origin, fishing technology, harvesting history, mariculture, variability, trophic groups, trophic level, future scenarios. Contents 1. Introduction 2. History of human harvesting technology 3. Harvesting marine biological resources 4. Future challenges and scenarios Glossary Bibliography Biographical Sketches To cite this chapter Summary The human species descended most probably from an early primate that lived and collected its food in shallow marine waters some 7 to 9 million years ago. The evolution of our brain and species has always been closely related to the resources of the ocean. Methods for catching fish have been known since the earliest days of mankind, involving spearing, harpooning, trapping, catching with hooks, and use of nets. Seagoing craft were developed 5000 years ago. The Industrial Revolution had its impact on fisheries, and the Second World War led to rapid development of technologies. Another important issue was the development of synthetic materials for boats and nets. This enabled the industry to develop highly efficient mid-water trawls and power systems to handle these. The first generation mariculture farms were established towards the end of the twentieth century. The harvesting potential of the ocean is 100 million tonnes/yr. FAO statistics show that harvesting is primarily undertaken in the coastal ocean. The total marine harvest is in the range of 105 to 110 million tonnes/yr, but only mariculture has increased since 1990. Harvesting is most likely beyond the level of exploitation that secures an optimal multi-species yield of marine resources. We exemplify the importance of variability in time and space and trophic position. Studies have concluded that improved technology and increased demands for seafood rather than over-exploitation of higher trophic levels is the mechanism that control development and composition of catches. Humans feed two trophic levels higher in the marine food web than in the agricultural one, and 99% of the marine primary production is lost. The potential to enhance marine

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harvesting is to catch and culture more organisms at lower trophic levels. We present three scenarios predicting future fisheries and mariculture activities. These scenarios assume different availability of marine resources for mariculture feed. 1. Introduction A current belief among many evolutionary biologists is that the human species descend from an early primate that lived and collected its food in shallow marine waters some 7 to 9 million years ago. This theory is in opposition to the traditional belief that our species developed on the savannah after leaving the trees. Many morphological and behavioural characteristics support the idea of an early marine or coastal phase, for example our hairless skin and our new-born children’s ability control breathing during swimming. There are many other characteristics that points to our marine origin as well, but our large and well developed brain that is a prerequisite for our superior mental capacity compared to other animals is suggested to be the strongest indication. It seems well documented that the brain size of terrestrial animals has not kept pace with the general increase in body weight of the animal during the course of evolution. This is particularly apparent for herbivorous animals feeding on plants, and extremely low brain to body ratios characterised the large plant eating dinosaurs. Michael Crawford has been a pioneer in developing these theories on human evolution, claiming that only animals feeding on marine food were able to maintain a high brain to body ratio as body size increased during evolution. The theory implies that the quality of the diet may constrain specific evolutionary developments, and the specific example of seafood and brain is quite easy to understand. Our brain and nervous system is built up of long chain omega 3 (ω3) fatty acids that are found in high amounts only in marine and freshwater organisms. The most important fatty acid is docosahexaenoic acid (22:6ω3, DHA), which is crucial for both vision and mental processes. Humans and other animals are only able to a limited extent to synthesise DHA, which therefore must be supplied in the diet. Michael Crawford and colleagues has postulated that a high intake of DHA in the food was crucial for developing the brain capacity of our species in the course of evolution. With this evolutionary perspective in mind, we may conclude that the modern human species in many ways originates from the ocean. Contrary to other marine mammals, we never left the shore, but remained partly in the terrestrial hemisphere with its characteristic challenges as driving forces for further evolutionary developments. Crawford and colleagues have recently provided support for the idea that the modern human species, Homo sapiens sapiens, developed in southern Africa some 100 000 years ago and that food items with high ω3 fatty acid content was indeed an important components of their diet. Seafood thus contributed to make humans mentally superior to other animals, and it made us in turn able to develop tools and technologies to make life easier. We have continued to harvest food and material from the ocean, and these tools and technologies include those needed to harvest food more efficiently from the sea. These tools in turn made us able to exploit all the major fish stocks of the global oceans. A couple of generations ago, no one would believe that this could be possible. However, there is currently ample evidence that we today over-exploit the marine biological resources of


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the world’s oceans. Many policy makers as well as scientists now call for improved management regimes. When the steady increase in harvesting of marine natural resources levelled off in the early 1990s, a major new event was already discernible. The developments of mariculture was in rapid progress, involving cultivation methods that with varying extents of intervention with nature make it possible to enhance and control production. Most likely this development will continue, starting some 9000 years after the first efforts to culture plants and to domesticate animals on land. This represents a shift in paradigm, we are making predictions for the future but are, of course, unable to see how things will actually develop. In any event, the fatty acids found in seafood will still be important for human’s mental capacity and ability to solve future problems and challenges, including our future exploitation of marine biological resources. 2. History of human harvesting technology Methods for catching fish have been known since the earliest days of humankind. The design, manufacture and use of fishing gear is one of our oldest technologies. Improvement of existing techniques and the development of new ones have continued right up to the present. Remains of pre-hominids have been excavated in northern Tanzania together with bones of fish and pebbles that may have been shaped by those creatures as tools for killing fish. Such pebbles may have been the fishing gears of creatures before the advent of Homo sapiens. In those days, and some times even today, fishing might be considered to be nothing more than gathering, the simplest form of economy known to man. In their natural state, the world’s oceans provide a rich variety of suitable materials of vegetable or animal origin. Fishes may belong to the most important group, but it is improbable that humans in prehistoric times would have been able to catch the fast-moving animals on a regular basis. It is more likely that the catches would consist of plants and slow-moving animals like molluscs, worms and crustaceans. Today fish provide a significant percentage of the foodstuff consumed by humanity. However, great volumes of algae and water plants are also harvested. They are used for human food and animal feed as well as for fertiliser, and for the extraction of chemicals, pharmaceuticals and cosmetic products. A global review of fishing methods may easily lead to the conclusion that there are innumerable ways of catching fish. However, in his classic book, “Fish Catching Methods of the World”, the German scientist Andres von Brandt concluded that there are only a dozen or so different basic principles for fish catching. The origins of the various methods of fishing are rather obscure. Ethnologists have found striking similarities in the fishing methods in primitive fisheries in different parts of the world. Most likely, fishing has represented similar challenges and opportunities all over the world, leading to the development of more or less identical solutions in different parts of the world. However, there are instances from the last couples of millennia, where methods for fishing have migrated over very large distances. Fishing and hunting may be traced to the same origins, and between them there has always been an interchange of techniques, such as spearing, harpooning, trapping, catching with hooks, and the use of nets. It is interesting to note that modern fishing


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with all its sophisticated equipment still contains strong elements of hunting, and in fact is considered a form of hunting by the industry itself. Early man was only interested in catching enough for the daily needs of his family. As time passed, coastal people became aware of the seasonal variations in the abundance of the fish species they caught, and started to use storage ponds to ensure a sustained food supply. There is evidence of such activities from ancient Greece. With the advent of methods for preserving fish, such as smoking, drying, salting and fermentation, it became possible to catch greater quantities of fish for storage and future consumption. Preservation also led to barter and trade with fish. Dried cod became Norway’s first export commodity more than 1000 years ago, and is still exported to the same markets as in the olden days. The first inhabitants along the coast of Norway, the way to the North, arrived as the last Ice Age came to an end. The main attraction was the abundant fish stocks in the ocean. They settled along the barren coast to exploit the riches of the sea. Some 8000 year old fields of pictographs (rock carvings) found in Norway depict boats and scenes from fishing activities. Interpretations of these pictographs suggest that the boat played a central role in the religious system of the time, and that it was an artefact of great importance to the people. As the Norseman developed his seafaring skills, the basis for the development of ocean-going craft was probably the technologies used for constructing fishing vessels. Archaeological findings support such a notion. Most likely the people of the North developed their Viking longships from smaller vessels used in fishing activities. Vessels of this type were used for crossing the Atlantic and settling on the shores of Newfoundland 500 years ahead of Columbus. Norsemen were probably the first explorers to discover the prolific cod stocks inhabiting the cold Atlantic waters of North America. Their technology was, however, not able to support the logistics necessary for the long term development of these settlements. Some archaeologists have claimed that there are reasons to speculate on possible transfer of fishing technology across the Atlantic in both directions. However, seagoing craft were developed independently in many parts of the world. In Europe, the people of the Mediterranean established ocean-going trade more than 5000 years ago. Archaeological evidence indicates that this had its origin in fishing activities as well. One of the oldest surviving vessels is an Egyptian ship, built 3000 years BC. The early Pacific islanders added outriggers and sails to their near-shore canoes, and were able to fish offshore for migratory fish such as tuna. This was probably the basis for the colonisation of the pacific islands 4000 years ago. Their vessels were extremely fast and seaworthy, enabling the islanders to travel vast distances. Magellan observed these vessels in the Pacific on his circumnavigation of the globe. He actually tried to measure the speed of these craft by using his European tools for measuring ship´s speed. He failed to do so because the maximum speed that his log could register was 12 knots. His estimate of their speed was twice that, 24 knots. He reported that they were by far the fastest vessels known to man. In the Age of the great explorations, abundant fish resources were discovered, such as the Newfoundland cod. Following the great explorer John Cabot, the Basque, the French, the British and the Portuguese established a migratory fishery in the early


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1500s. Two types of fishing were carried out, the wet fishery, and the dry fishery. The wet fishery was carried out offshore, on the banks. The fish was simply gutted, split and salted on board, and taken back to Europe. The dry fishery produced bacalao for the southern European market. Hundreds of vessels crewed by 20 to 40 men, left the shores of Europe in early summer to fish for the cod. The fish were caught from small boats in near-shore waters. There were usually three men in each boat using baited hooks on hand-lines. A shore crew gutted, split and salted the fish, later to be dried in the sun and wind on the beach. In the mid-1800s, dory-fishing schooners from New England and the Canadian East Coast dominated the cod fisheries on the banks off Nova Scotia and Newfoundland. Europe saw development of fisheries for pelagic species like sardine and herring. Fishermen from southern Sweden started catching North Sea herring spawning on their coast in the eleventh century. As the migration pattern of the herring stocks changed over the centuries, fishing vessels from most of the nations around the North Sea participated in the herring fisheries, using drift-nets and preserving the fish in barrels with salt. In the 1600s, sardines were caught with fine mesh nets in France, off the Breton coast. The catch was sold fresh or salted, but later on technology was developed for producing sardine oil, which became a popular commodity all over Europe. An important offshore fishery for tuna developed in the Bay of Biscay, the fish being caught by trolling lines. By the mid 1800s, canneries were in operation in many parts of Europe. Sardines and tuna were popular for canning. These events could be considered the start of industrialisation in the fishing industry. The Industrial Revolution rapidly had its impact on fisheries in Europe and North America. British fishermen had introduced beam trawling with sailing vessels in the North Sea in the early 1800s. With the advent of the steam engine, and its subsequent introduction into ships, mechanical propulsion for the first time became available in fisheries. Paddle steamers were used for bottom trawling in the North Sea in 1860, and in the 1880s steam trawlers began replacing sailing vessels. The beams used for spreading the nets were difficult to handle, and limited the size of the fishing gear. For better utilisation of steam power, the otter trawl was developed. These nets were more suitable for fishing on rough sea bottoms. The first otter trawl was constructed in 1892 in Scotland. This fishing gear consisted of a conical net with the mouth extended into wings. These were attached to and spread by otter boards or trawl doors, as they were called in the colloquial. These doors were large door-like wooden rectangles heavily weighted with iron shoes, towed from the trawler by steel ropes. Water pressure against the boards kept the net open. At the turn of the nineteenth century, the first steam trawlers appeared in North America. The success of these ventures was moderate at first. This was, however, the starting gun for a large trawl fishery on Georges Bank and Grand Banks. This activity was later to be joined by most major fishing nations, an intensive activity that might be a primary cause of the collapse of the Newfoundland cod stocks. In Scandinavia the mechanisation of fishing took a different course. From about 1900 simple small oil engines were constructed in blacksmith shops along the coast. Tens of thousands of these engines were installed in the fishing fleet before World War 1.


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Efforts by merchants to gain control over the fishing fleet by the introduction of capital intensive vessels were unsuccessful, and the ownership of the fishing fleet remained to a large extent with the fishermen. Steam winches had been introduced into the trawler fleet to handle the steel warps used for towing and to ease the toil of the fishermen when handling the nets and the catch. The lack of steam power suitable for smaller vessels led to a quest for finding other power sources for mechanising fishing operations and gear handling on fishing vessels. This led to the use of internal combustion engines. In the 1920s the first engine-powered mechanical hauling devices were constructed. The invention of the low-pressure hydraulic system was an important breakthrough in fishery technology that followed ten years later. This became a boon for fishermen in many parts of the world, being a very robust system that gave fingertip control of fishing and gear-handling operations. In the 1820s, ice was introduced as a means to prolong freshness, but it would take another 100 years before the American Clarence Birdseye introduced the freezing of fish into fisheries. He had made experiments with freezing of food for years and he later founded the company Birdseye General Seafood. World War II led to a rapid development of a variety of technologies, some of which later proved to be of great importance for the fisheries of the world. The development of acoustic equipment for detection of submarines spurred the construction of very efficient devices for fish finding and surveillance of fish-stocks. Modern fishing would hardly be conceivable without echo sounder and sonar. Of similar importance was the development of radio navigation systems such as Decca, Loran and the more recent satellite navigation systems. Radar, developed for detecting enemy ships and aircraft, has greatly improved safety for the fisherman, and his ability to fish under severe weather conditions. The combination of position-finding devices and radar has made retrieval of stationary nets and long-lines infinitely easier. Another vastly important change was the rapid development of new synthetic materials for boat building and net-making. This enabled the industry to develop impressive fishing gear like enormous mid-water trawls and vast purse seines with enormous catching power. The handling of large size nets has been facilitated by inventions such as the hydraulic power block, invented on the US West Coast in the 1950s—another milestone in the history of fisheries. This long row of innovations made possible the development of the factory ship. These are large diesel-powered vessels combining the use of high-tech fish finding and navigation equipment with the use of huge nets made from synthetic fibres, filleting machinery, and rapid freezing technology. Large armadas of such ships have been roaming the oceans for several decades, exploiting and over-exploiting fish stocks in international waters. The development of mariculture is in its beginning. The developments have gone from production of zoobenthivores and large algae in open or closed coastal locations or ponds to land based farms, for example producing shrimps, and sea cages used for fish. Cages have been shown to be very efficient and cost effective for fish production. An


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efficient generation of land based and cage based mariculture farms was established at the end of the twentieth century, but developments in mariculture are most likely still in a very early phase. Coastal waters are normally exposed to strong winds and currents, at least occasionally. Sea cage systems developed for exposed or partly exposed regions will become a technological challenge of great importance because this technology will increase the area available for mariculture and reduce possible negative interaction with society. 3. Harvesting marine biological resources Humans have harvested marine biological resources for a long time, but mariculture has gradually become increasingly important during the latter part of the twentieth century. These recent developments are in many ways comparable to those of agriculture that took part some 8000 to 9000 years ago. Mariculture has a long tradition, but it has been developed more rapidly since marine harvesting levelled off in the early 1990s (see below). The triggering mechanism for starting cultivation is therefore most likely the need to produce more food, comparable to what initiated agriculture when harvesting nature became insufficient for feeding the growing human populations. The early developments of mariculture have of course taken advantage of a far longer tradition of culturing freshwater fish. There has also been some cultivation in coastal waters in earlier times, in particular in well-developed cultures and densely populated areas of the world. Other important factors that have made developments possible are increased knowledge on the marine ecosystem, technological development, and more knowledge and experience in managing marine biological resources. The current cultivation efforts of the sea involve a wide range of methods. These includes moderate intervention with nature during sea ranching, which normally involve release of juveniles and sometimes also improvements of their habitat, and the far stronger intervention that is associated with intensive cultivation. Intensive mariculture represents cultivation with efficiencies far higher than the carrying capacity of nature and can in many ways be compared with modern agriculture. Extensive mariculture, like for example sea ranching, is more comparable with cultivation methods used in forestry. 3.1. Global potential and distribution of harvesting Fishermen in ancient Greece had discovered that recruitment was important for future catches. It was, however, not before the twentieth century that man became aware that the biological resources of the ocean were limited, and that we had the technology to overexploit and exhaust these resources. Many authors believed and claimed that the oceans were inexhaustible. It was after 1950 that the first estimates of the global potential for harvestable biological resources appeared. The methods used to estimate the global harvesting potential were diverse, sometimes based on empirical experience from fisheries of demersal and pelagic species, and other times on theoretical analysis based on simple trophic models. Many estimates originated from a mixture of these methods. The simple trophic models used predict production on given trophic level n (Pn) as a function of the primary production (PP), the conversion efficiency of energy (E) from one trophic level (n) to the next (n+1):


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Pn = PP En-1 (1) The primary production of the phytoplankton will then be assigned to trophic level 1 (P1) whereas herbivore animals will represent trophic level 2. The value of the conversion efficiency (E) for the marine food webs was normally assumed to be 0.1 to 0.2 (10 to 20%), but this issue is still a matter of debate. Another issue of controversy, which indeed also affected the outcome of the estimations, has been the trophic level of the important species and stocks. Estimates made for the potential fisheries of the ocean made in the period 1950 to 1999 differed by almost two orders of magnitude, from 22 to 2000 million tonnes per year. Many of the estimates published from 1965 were in the range 100 to 200 million tonnes per year, and the former value has more recently become the authorised figure of FAO. John Ryther was the first to come up with a prediction for the potential fisheries of the ocean of 100 million tonnes per year. He divided the global oceans into three provinces each with characteristic primary production, food web structure, and ecological efficiencies:

• The open ocean – 326 million km2, 89% of the ocean surface. Primary production of 50 gC m-2 day-1, ecological efficiency of 0.1, and 5 trophic steps of the food web.

• Coastal waters (<180 m depth, including offshore regions of comparable productivity) – 36 million km2, 10% of the ocean surface. Primary production of 100 gC m-2 day-1, ecological efficiency of 0.15, and 3 trophic steps of the food web.

• Upwelling systems – 3.6 million km2, 1% of the ocean surface. Primary production of 300 gC m-2 day-1, ecological efficiency of 0.2, and 2.5 trophic steps of the food web.

Based on this classification, and of course his vast experience in the field, he came up with a prediction of 240 million tonnes fresh weight of fish produced annually, of which 100 million tonnes were regarded as harvestable for humans. Other implications of Ryther’s analysis were that coastal upwelling areas were highly productive, whereas the majority of the open ocean was highly oligotrophic, termed marine deserts from a harvestable production point of view. The coastal marine systems were normally intermediate. He found that as much as 50% of the global harvestable production took place in the major coastal upwelling systems of the Earth, which constitute only 1% of the ocean surface. The next 50% of the production potential was located in the 10% which are coastal waters, whereas the 89% surface which was defined as open ocean, was responsible for <1% of the production. Later contributors have criticised Ryther both for using too high trophic levels for the harvested resources from open ocean and coastal waters and for using too high ecological conversion efficiencies for the upwelling regions. New experimental evidence is still being collected to improve the knowledge of energetics of the marine ecosystem and the realism of the estimates derived from trophic models. Strong evidence has been provided for an ecological conversion efficiency of 0.1 also in


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upwelling systems. This will reduce Ryther’s estimate of the production potential of the coastal upwelling systems and modify the distribution between his regions, in agreement with estimates based on fishery statistics. For Ryther’s estimates, this effect is counteracted by the fact that Ryther most likely assumed too many trophic transfers. Many other issues of management, biological, economic, and political nature will, of course, affect the global catches of today, but Ryther’s estimate is still apparently viable—it may have been right for the wrong reasons. Global fishery statistics are collected by the Food and Agriculture Organization of the United Nations (FAO). Their Fishery Statistics Database uses defined FAO Fishing Areas. The data for the Fishing Areas (see Figure 1) express catches and not the biomass of the stocks. For characteristic features of the areas, see Tables 1 and 2)

Figure 1. FAO fishing areas defined for statistical purposes (see further geographic definitions and productivity data in Tables 1 and 2). Source: FAO Capture Database.

3.2. Overall harvesting history FAO statistics reveal that the total harvest of marine biological resources, which is the sum of resources extracted through fisheries (termed ‘harvested’) and biomass from mariculture (termed ‘cultured’), has, with minor fluctuations, showed a relatively steady increase of 1.85 million tonnes per year over the last half century. This increase corresponds to an increase rate of 1.8% per year during the 1990s (see Figure 2). The marine harvest had a steady increase during the 1950s, but the increase showed a shift upwards at the end of the decade. The increased production was primarily a result of the implementation of new and improved technology and materials (see above). The fast and steady increase in harvesting lasted until about 1970. Since then, harvesting has increased far slower and has in fact levelled off at 80 to 85 million tonnes from the late 1980s. There may be minor stocks that are still under-exploited, but it is a general view that harvesting today is beyond the level of exploitation that secures an optimal multi-species yield of marine biological resources. It is a current matter of discussion whether our harvesting is sustainable in the long term, and a precautionary approach is needed because of the complex nature of the problem. A major uncertainty for the estimation of


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maximum sustainable harvesting is the lack of information on quantities that are lost or discarded during fishing. It is a general assumption that as much as 25 to 30% of the catches are lost or discarded, mostly as a result of economic and political conditions. Reducing this by-catch loss is, of course, a major challenge, both from resource availability and management perspectives.

Figure 2. Developments in marine harvest (fisheries), mariculture and total marine harvest (sum of fisheries and mariculture) durting 1950 to 1999. Marine mammals are

excluded.Source: FAO Capture Database. Mariculture has a long tradition, but the historical and economic importance of mariculture has been low compared with freshwater aquaculture. Developments increased slowly over the last century, with an accelerated increase of yields from the early 1990s, approximately at the time when harvesting rates levelled off. This is most likely not accidental, and it probably reflects the results of greater attention to and investments in mariculture research, developments and production. It is notable that the increase in mariculture yields with time has now quantitatively replaced the earlier increases in harvesting—the pattern of increase in total harvesting is steady at 1.85 million tonnes per year in the 1990s (see Figure 2). It is an interesting question, if this trend will continue in the same way as we have seen in agriculture. An important constraint for a similar development of mariculture is the fact that most species of cultivated fishes and shrimps depend on feed from the ocean. This means that mariculture to a certain extent represent protein and lipid refinement rather than new resources (see further discussion below). It is nevertheless an efficient means of increasing the value of the harvested marine biological resources that are not currently used for direct human consumption. Marine animals like, for example, Atlantic salmon utilise their food far more efficiently than the warm-blooded animals of agriculture.


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The total marine harvest is 4.3 times higher than the total harvest in freshwater, which also has shown a pronounced increasing trend during the last few decades (see Figure 3, upper panel). A major difference is, however, that the majority of the freshwater production originates from culture, whereas fisheries dominate the marine. The harvest from freshwater aquaculture was 18.3 million tonnes in 1999 whereas the harvest from mariculture was 23.1 million tonnes. Yields of mariculture and freshwater culture have developed equally during the last 30 years (Figure 3, lower panel), but the products are different. Finfish is the dominating product from freshwater aquaculture, with the Chinese production of carp as a main component. The majority of the production in mariculture is marine macroalgae (seaweeds), which indeed has shown a remarkable increase during the last decade. Finfish is still a minor product in mariculture. The most successful finfish cultivation in the sea has been that of salmonids grown in sea cages.

Figure 3. Total harvest of marine and freshwater biological resources. Upper panel: total marine and freshwater harvest during the period 1950 to 1999. Lower panel: harvest


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from mariculture and freshwater culture during the period 1970 to 1999. Marine mammals are excluded.Source: FAO Capture Database.

3.3. Important species of trophic categories The FAO capture database includes a very high number of species in the global catches, but some species are obviously more important than others. Caddy and Garibaldi have identified such Key Species in four main trophic categories of 15 important FAO Fishing Area, and these species are summarised in Table 1. Their trophic categories involve piscivore, zooplanktivore, zoobenthivore and herbivore species. The species were assigned to these trophic groups based on research and local fishing experience. Five species were identified for each trophic category, which means 20 selected Key Species per FAO Fishing Area. The selected Key Species constituted on average 62% of the total catches in the period 1950 to 1997, but their contribution to the total harvest in the individual FAO Fishing Area was highly variable (ranging from 11 to 96%). The Eastern Indian Ocean showed the highest diversity in the catches from 1950 to 1997. The 20 Key Species constituted only 11% of the total catches in this area. The Southeast Pacific showed the lowest diversity, where the Key Species constituted as much as 96% of the catches.

Key species Fishing Area Piscivores Zooplanktivores Zoobenthivores Herbivores

21 Northwest Atlantic

Atlantic cod, Silver hake, Saithe, Greenland halibut, Northern shortfin squid

Atlantic herring, Atlantic menhaden, Atlantic mackerel, Capelin, Roundnouse grenadier

Haddock, American Plaice, American lobster, Blue crab, Northern prawn

Am. sea scallop, Am. cupped oyster, Atlantic surf clam, Ocean quahog, Northern quahog

27 Northeast Atlantic

Atlantic cod, Saithe, Atlantic horse mackerel, Whiting, European hake

Atlantic herring, Capelin, Atlantic Mackerel, European sprat, Blue whiting

Haddock, European plaice, Northern prawn, Common shrimp, Norway lobster

Common edible cockle, Great Atlantic scallop, Iceland scallop

31 Western Central Atlantic

Yellowfin tuna, Atlantic Spanish mackerel, King mackerel, Albacore, Atlantic croaker

Round sardinella, Atlantic menhaden, Atlantic thread herring, Atlantic anchoveta, American shad

Northern brown shrimp, Blue crab, Northern white shrimp, Caribbean spiny lobster, Red grouper

Gulf menhaden, American cupped oyster, Calico scallop, Flathead grey mullet, mangrove cupped oyster

34 Eastern Central Atlantic

Yellowfin tuna, Skipjack tuna, Largehead hairtail, Bigeye tuna, Senegalese hake

European pilchard, Round sardinella, Chub mackerel, European anchovy, Madeiran sardinella

Common octopus, Southern pink shrimp, Lesser African threadfin, Deepwater rose shrimp, Red pandora

Bonga shad, Bogue, Black seabream, Flathead grey mullet, Common edible cockle

37 Mediterran-ean and Black Sea

Mediterr. Horse mackerel, European hake, Atlantic bonito, Northern bluefin tuna, Whiting

European anchovy, European pilchard, Azov sea sprat European sprat, Chub mackerel

Common cuttlefish, Common octopus, Deepwater rose shrimp, Common sole, Norway lobster

Mediterr. Mussel, Bogue, Striped venus, Flathead grey mullet, European flat oyster

41 Southwest Argentine hake, Brazilian sardinella Striped weakfish, River plata mussel,


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Atlantic Argentine shortfin squid, Whitemouth croaker Patagonian grenadier, Albacore

Southern blue whiting, argentine anchovy, Chub mackerel, Patagonian squid

Pink cusk-eel, Atlantic seabob, Argentine croaker, Castaneta

Brazilian menhaden, Argentine menhaden, Atlantic krill, Cholga mussel

47 Southeast Atlantic

Cape hakes Snoek Albacore Bigeye tuna, Largehead hairtail

Southern African pilchard, Cape horse mackerel, Southern African anchovy Cunene horse mackerel, Chub mackerel

Cape rock lobster, Kingklip, Crevalle jack, panga seabream, Deepwater rose shrimp

Perlemoen abaloneBlack seabream, Bogue, Salema, Red bait

51 Western Indian Ocean

Bombay-duck, Skipjack tuna, Yellowfin tuna, Narrow-barred Span.mackerel, Silky shark

Indian mackerel, Unicorn cod, Black pomfret, Silver pomfret, Chub mackerel

Giant tiger prawn, Mangrove red snapper, Knife shrimp, Fourfinger threadfin, Indian white prawn

Indian oil sardine, hilsa shad, Kelea shad, Flathead gray mullet; Milkfish

57 Eastern Indian Ocean

Southern bluefin tuna, Indian scad, Yellowfin tuna, Torpedo scad, Skipjack tuna

Indian mackerel, Goldstripe sardinella, bali sardinella, black pomfret, Silver pomfret

Australian spiny lobster, Giant tiger prawn; Green rock lobster, Blue swimming crab, Golden snapper

Hilsa shad, Indian oil sardine, Kelee shad, Blacklip abalone, Chacunda gizzard shad

61 Northwest Pacific

Largehead hairtail, Japanese flying squid, Skipjack tuna, Pacific cod, Japanese Spanish mackerel

Alaska pollock Japanese pilchard, Chub mackerel, Japanese anchovy, Pacific saury

Large yellow croaker Yellow croaker, Threadsail filefish, Gazami crab, Southern rough shrimp

Japanese carpet shell, Yesso scallop, Half-crenated ark, Flathead grey mullet, Hen clam

67 Northeast Pacific

Alaske pollock, North Pacific hake, Pacific cod, Coho salmon, Arrow-tooth flounder

Pacific herring; Pink salmon, Sockeye salmon, Atka mackerel, American shad

Pacific ocean perch, Yellowfin sole, Pacific halibut, Sablefisk, Dungeness crab

Pacific cuppenoyster Weathervane scallop, Butter clam, Pacific geoduck, Pacific razor clam

71 Western Central Pacific

Skipjack tuna, Yellowfin tuna, Kawakawa, Frigate and bullet tunas, Indian Scad

Goldstripe sardinella; Bali sardinella, Indian mackerel, Rainbow sardina, Short mackerel

Banana prawn, Bogeye scad, Blue swimming crab, Indo-Pacific swamp crab, Mangrove red snapper

Green mussel, Toli shad, Slipper cupped oyster Chacunda gizzard shad, Milkfish

77 Eastern Central Pacific

Yellowfin tuna, Skipjack tuna, Bigeye tuna, Jumbo flying squid, Striped marlin

California pilchard, Californian anchovy, Pacific anchoveta, Chub mackerel, Pacific jack mackerel

Crystal shrimp, Dungeness crab, Yellow snapper, Sablefish, Yellowleg shrimp

Pacific calico scallop, Pacific cupped oyster, Milkfish, Bobo mullet, Weathervane scallop

81 Southwest Pacific

Blue grenadier, Wellington flying squid, Greenback horse mackerel, Albacore; southern bluefin tuna

Southern blue whiting, Snoek, Australian salmon, Silver warehou, Blue mackerel

Orange roughy, Golden snapper, Tarakihi, Red rock lobster, Red coding,

New Zealand dredge oyster, New Zealand scallop, Blacklip abalone, Pacific cupped oyster, Australian mussel

87 Southeast Pacific

South Pacific hake, Eastern pacific bonito, Patagonian granadier, Yellowfin

Anchoveta (Peruvian anchovy), South American pilchard, Chilean jack

False abalone, Chilean nylon shrimp, Pink cusk-eel, Red cusk-eel,

Australian herring, Cholga mussel, Taca clam, Chilean sea urichin, Pacific


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tuna, Skipjack tuna mackerel, Chub mackerel, Pacific anchoveta

Black cusk-eel, menhaden

Table 1. Review of identified Key Species within trophic categories for the selected FAO Fishing Area, by Caddy and Garibaldi. The five most important species in each

trophic categoryare listed in order of importance. Table 2 summarises the total accumulated harvest and Key Species harvests made in the selected FAO Fishing Areas from 1950 to 1997, together with the total harvest for the year 1996. Both production figures and the relative distributions between the different FAO Fishing Areas are given. The FAO Fishing Areas have contributed differently to the total catches made through 1950 to 97, with a contribution range of 0.6 to 28% of total harvest. The Northwest Pacific (Area 61), the Northeast Atlantic (Area 27), and the Southeast Pacific (Area 87) are quantitatively the most important areas. This pattern is apparent both for the total harvest during 1950 to 1997, the harvest during 1996, and for the Key Species. Nine of the FAO Fishing Areas have relatively minor contributions in the range of 0.6 to 3.6% of the total catches.

Fishing Area 1996 harvest, mt

1996 harvest,

% of total

Harvest of Key Species, mt (period 1950-97)

KS harvest,

% of total

Total harvest, mt, (period

1950-97)

Total period, % of total

21 Northwest Atlantic 2,031,090 2.3 122,729,721 7.4 149,328,826 5.6 27 Northeast Atlantic 11,050,010 12.7 342,851,517 20.7 461,836,182 17.4 31 Western Central Atlantic 1,704,125 2.0 47,963,353 2.9 69,521,132 2.6

34 Eastern Central Atlantic 3,365,172 3.9 54,941,599 3.3 105,773,283 4.0

37 Mediterranean Black Sea 1,495,743 1.7 38,909,220 2.3 60,262,641 2.3

41 Southwest Atlantic 2,474,071 2.8 33,976,868 2.1 53,310,916 2.0 47 Southeast Atlantic 1,031,716 1.2 74,795,458 4.5 89,897,667 3.4 51 Western Indian Ocean 4,030,830 4.6 27,780,940 1.7 93,634,530 3.5 57 Eastern Indian Ocean 3,857,723 4.4 9,095,752 0.5 79,496,211 3.0 61 Northwest Pacific 24,966,291 28.7 365,227,503 22.1 734,234,098 27.6 67 Northeast Pacific 2,880,530 3.3 76,703,027 4.6 94,922,858 3.6 71 Western Central Pacific 8,838,518 10.2 43,689,218 2.6 208,409,229 7.8

77 Eastern Central Pacific 1,568,676 1.8 31,560,985 1.9 48,348,305 1.8 81 Southwest Pacific 638,806 0.7 9,957,677 0.6 17,015,676 0.6 87 Southeast Pacific 17,028,111 19.6 376,125,251 22.7 390,939,573 14.7 Total 86,961,412 100 1,656,308,089 100 2,656,931,127 100

Table 2. Review of harvesting history for the selected FAO Fishing Area and their relative percent contribution. Data are recompiled, based on Caddy and Garibaldi

(2000). Key Species are given in Table 1. 3.4. Case analysis of species variability The Southeast Pacific is a typical upwelling FAO Fishing Area characterised by a high fraction of zooplanktivore species in catches and high variability in catches with time.


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The most abundant species are Anchoveta (Peruvian anchovy) and South American pilchard, both zooplanktivore species (see Table 1). Anchoveta is one of the most abundant species of catches worldwide, and Figure 4 illustrate its major oscillations and high abundance in the catches all through the period in the Southeast Pacific. It is noteworthy that the catches of anchoveta constituted as much as 23% of the global catches in 1970 just before it collapsed, reaching catches close to zero in 1982/83. The species recovered relatively rapidly later in the period. Other zooplanktivore species like South American pilchard and Chilean jack mackerel increased their abundance in the catches at the time when the anchoveta became almost extinct. This may have been an effect of interspecies competition for food, but it may also have been caused by changes in fishing efforts.

Figure 4. Variability in harvesting yields of the most abundant zooplanktivore species in the Southeast Pacific during 1950 to 1999. Source: FAO capture database.

A second major FAO Fishing Area is the Northeast Atlantic, classified as a temperate area characterised by a higher ratio of piscivores to zooplanktivores in catches. By far the most dominating piscivore fish species in catches made in the Northeast Atlantic is the Atlantic cod, a highly appreciated species that has affected the history of the North Atlantic countries for more than a thousand years. The catches of Atlantic cod have decreased over the three last decades (see Figure 5, upper panel), and this is the case also for the Northwest Atlantic. It is generally assumed that the species is over-exploited for the time being. It is typical, therefore, that major effort are now being


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made in many northern Atlantic countries to bring Atlantic cod into culture. This is but one example of the general trend that reduced catches and overexploited stocks of high value species results in increased efforts in mariculture.

Figure 5. Catches of Key Species in the Northeast Atlantic during 1950 to 1999. Upper panel: harvesting yields of the five most important piscivore species. Lower panel:

harvesting yields of the five most important zooplanktivore species. Source: FAO capture database.

Figure 5 illustrates how the catches of piscivore and zooplanktivore Key Species in the Northeast Atlantic have varied during 1950 to 1999 along with the quantitative importance of these Key Species. Atlantic cod has always been the most important piscivore species in this area (Figure 5, upper panel), with Saithe (or Pollack), and more recently also Atlantic horse mackerel, following after. The catches of all piscivore species except the horse mackerel have diminished in recent decades. Zooplanktivore catches have, like those in Southeast Pacific, been characterised by far higher variability


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with time than piscivores. Atlantic herring and capelin are the most important zooplanktivore species. Their contribution to the global harvest in their peak year of harvest was 8.1% for herring in 1965 and 6.3% for capelin in 1977. Atlantic mackerel, European sprat and blue whiting are important species that have shown more steady yields since they started to become exploited. It is remarkable how the catches of herring and capelin seem to vary out of phase. This most likely reveals a related variability in their biomasses, at least from 1970. The capelin has apparently taken advantage of a major reduction in herring in the last part of the 1960s, meaning that the two species exploit the same prey. The Norwegian spawning herring became almost extinct at that time, and is just recently re-established in viable populations. The rapid reduction in herring catches has traditionally been believed to be a result of over-exploitation, but other causes may also have contributed. Whether over-exploitation was the only reason or not, this event clearly showed that humans had certainly acquired the technology to exhaust major fish populations from the sea. 3.5. Variability and trophic composition A characteristic feature of the Northeast Atlantic area was the high yields of piscivore species in the catches (see Figure 6, upper panel). The development of the piscivore catch is comparable to those for Atlantic cod. The harvest of zooplanktivore Key Species has in fact increased steadily all through the period from 1950 to 1999 and the ratio of piscivore to zooplanktivore has decreased at the same time (Figure 6, lower panel). An increase in the fraction of stocks feeding on low trophic levels relative to those that feed on high level is quite common, and this finding has resulted in discussions of ecosystem health among policy makers and scientists. Some has interpreted this pattern as a result of over-exploitation of attractive carnivore fish stocks that normally feed on planktivore stocks of fish (“Fishing down marine food webs”). For the Northeast Atlantic, there was no statistical correlation between catches of piscivores and zooplanktivore Key Species for the period 1950 to 99 (Figure 6, r2 = 0.028). This suggests a rather weak trophic interaction between the groups. The high ratio of piscivore to zooplanktivore in the catches moreover suggests that only a low fraction of the zooplanktivore production is harvested. Far more zooplanktivores should be consumed by the piscivores that at the end becomes harvested, if we are to assume an ecological conversion efficiency of 0.1. It is difficult to understand that over-exploitation of piscivores is the main controlling factor for the catches of zooplanktivores. Caddy and Garibaldi have analysed the causes behind the apparent changes in the trophic composition of world marine harvests, and they do this for the important FAO Fishing Areas based on data in the FAO capture database. They conclude that improved technology and increased demands for seafood in the rapidly developing world markets, rather than over-exploitation of higher trophic levels is the mechanism behind the reduced trophic level of the catches. However, they still agree that most fisheries now are beyond the optimal level of exploitation.


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Figure 6. Catches of piscivore and zooplanktivore Key Species in the Northeast Atlantic during 1950 to 1999. Upper panel: total catches of piscivores and zooplanktivores

(>50% of total catches). Lower panel: ratio of piscivore to zooplanktivore representatives for the Key Species. Source: FAO capture database.

The question of trophic position of the harvest of marine biological resources has another perspective, which tends to be underestimated in the evaluations of future fishery strategies. It is to be regarded as a law of nature that some 90% of the energy is lost in each trophic transfer of the primary production in the food web. It is also beyond any doubt that we tend to harvest food from higher trophic levels in the ocean than on land. A comparison between human’s agriculture and seafood chains is useful to illustrate an important constraint of the marine harvesting potential. The global terrestrial and marine primary production is generally assumed to be of the same magnitude, but marine food contributes little to the human food supply (1 to 2%). Figure 7 illustrates human feeding habits for typical products from seafood and agriculture, or the human trophic position for these types of food. In the agricultural


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food web, humans primarily feed on the primary producers and animals that feed on primary producers. Food items from higher trophic levels do not contribute significantly to the global food supply. It may accordingly be deduced that we feed between trophic level 1 (plants) and 2 (grazing animals) in the agricultural food web (herbivore-omnivore), which means 0 to 1 trophic transfers of the primary production, closer to 0 than to 1 because we eat more plants than meat.

Figure 7. Schematic illustration of the trophic levels in the agriculture food chain and seafood food chain for humans. Our food from the agriculture food chain is harvested

approximately two levels lower than in the seafood web. In the marine food web we consume very marginal amounts of marine plants and herbivore animals that feed on algae (e.g. mussels). Carnivorous animals (e.g. zooplanktivore) and species even higher in the food web (e.g. piscivores) are, however, the most important commercial resources harvested from the ocean. A significant


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fraction of the 1st level carnivore stocks is that they are only used indirectly for human consumption, as they are generally refined through mariculture, freshwater culture or agriculture. The overall result is that we most likely feed between levels 3 and 4 (1st and 2nd carnivores) in the marine food web, meaning that the primary production has passed 2 to 3 trophic transfers before human consumption. These considerations are of course over-simplifications, but they are still relatively robust. Humans feed about two trophic levels higher in the marine food web than in the typical agricultural one, and 96 to 99% of the marine primary production is lost during these two extra trophic transfers. Because the marine and terrestrial primary production are of the same magnitude, these figures are compatible with FAO statistics showing that only 1 to 2% of the total energy available to humans originates from marine primary production. The contribution of proteins becomes higher, because we primarily feed on marine animals. It is a relative robust conclusion that our current harvesting strategies of marine biological resources make a major increase in marine harvest impossible. The huge potential to enhance the marine harvesting of bio-resources is to catch the steadily declining assimilated carbon before conversion to carbon dioxide during respiratory processes. In other words this implies harvesting, and indeed also cultivation, of organisms feeding at the lower trophic levels. This is of course impossible using current technology, but our earlier experiences suggest that lack of suitable technology is only a temporary hindrance. The idea of implementing a “bottom up” strategy of harvesting marine biological resources instead of the common “top down” strategy of today should be thoroughly evaluated, because the consequences are still unknown. There is a chance that a controlled harvesting from lower levels that are based on knowledge on the structure and functioning of marine ecosystems may contribute to alleviate fishing pressure on both zooplanktivore and piscivore fish stocks. The marked driven requests for marine feed for mariculture is one force that may speed up developments, because lack of such feed resources will become a limiting factor for further mariculture developments in a decade or two. 4. Future challenges and scenarios The political, social and demographic development of the global human population will most likely become a powerful driving force for further increases in fisheries and mariculture activity during the twenty-first century. For our prediction of the future development from 2000 to 2050, we assume that:

• The global population will develop as predicted by UN, reaching 10 to 12 billion people by 2050.

• There will be a steady increase in demand for seafood in the world market. • An international and powerful management regime for marine biological

resources will be established and implemented. Global taxes on harvests will provide the funds needed.

• The emission of toxic substances to coastal waters is phased down thanks to international agreements.


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• Technology will never be absolutely limiting for fisheries and mariculture developments.

It is generally believed that any substantial increase in marine harvest in the future must come from mariculture and not from the heavily exploited natural stocks. A comparable development took place in the terrestrial hemisphere when agriculture gradually took over from hunting in ancient human communities, and the driving force of this process was most likely the increasing needs for food of the growing population. The domesticated animals were easily controllable herbivores that exploited plants from nature. Comparable activity in the sea is named sea ranching and it involves release of juveniles, and sometimes also improvements of habitats, but this activity is far more complicated and economically questionable than animal farming on land. Sea ranching was intensively studied from the early twentieth century in Europe and USA, but is now implemented only in Eastern Asia where this type of mariculture has a stronger tradition. In traditional mariculture, the cultured species are maintained under more strict control, and one consequence is that we need to provide fish food. Marine species require food of marine origin, or more specifically they need to be supplied with long chain ω3 fatty acids such as DHA (see above) and EPA (eicosapentaenoic acid). Mariculture can therefore not easily be based on proteins and lipids from agriculture. This fact represents a major potential constraint for developing mariculture during the next century, because the feed resources (1st carnivore fish, not plants) are not as easily available as in agriculture. It is therefore not obvious that mariculture will become as successful as agriculture. There are potential ways to provide more ω3 fatty acids for mariculture. We may for example:

1. Change our harvesting strategy and harvest more herbivore animals from the sea.

2. Produce feed based on macro-algae. 3. Produce herbivore marine animals that are used for feed, e.g. mussels. 4. Produce marine quality lipids and proteins using fermentation technology.

We will not comment on the use of macro-algae for feed, but elaborate on the possibilities of harvesting herbivore animals, i.e. zooplankton. Some regions of the world’s oceans have large stocks of herbivore copepods and krill that are abundant and potentially exploitable, depending on their distribution in time and space. Ten percent of the annual herbivore production is in theory comparable to the entire production of zooplanktivore fish (1st carnivore), and 1% is still a significant resource. If zooplankton production in the sea tends to be food limited, we may expect that moderate harvesting primarily will result in less mortality of zooplankton and not necessarily in reduced standing stocks and availability for planktivore fish. The fact that the zooplankton is food for important fish stocks brings up management and political dimensions, and the potential interaction with fisheries must therefore be thoroughly examined. If we implement controlled production of the food used in mariculture, this will represent a new paradigm. It was in the twentieth century that man first started to feed the domesticated animals by providing cultured plants as a supplement to harvested


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plants. This was made possible by the introduction of artificial fertilisers and improved technology, and it represented a new step towards full control with the agriculture cycle, which thereafter has developed very rapidly to the western type of highly industrial and controlled agriculture of today. To produce mussels for fish feed may seem unlikely today, but mass production of a “single cell protein” of marine quality seem more feasible and closer. A micro-organism with marine lipids that can be grown based on for example sugars or methane is probably not yet available, but it will certainly be searched for. It is most likely that such an organism will be produced using modern genetic methods. An alternative is that genetically modified higher plants will be used to produce marine lipids. Base on the above premises and discussion, we assume that mariculture development will be heavily dependent on our ability to find new marine feed resources. The situations that may develop are illustrated by the following three scenarios for 2050, which indeed are both subjective and speculative. One scenario assumes that no new marine feed resources become available in the period (2000 to 2050). The second scenario assumes that a major resource is derived through harvesting herbivore zooplankton. In the third scenario we take additional control in the cultivation process of mariculture by producing parts of the feed, like in modern western agriculture. Scenario 1: No new marine feed resource for mariculture is made available Global fishery activities have continued along relatively traditional lines. The global harvest of fisheries is 120 million tonnes, thanks to a better understanding of the marine ecosystem, reduction in losses, improved harvesting technology, strategic use of nutrient emission from agriculture for production in the coastal zone, and new efficient international regulations and management principles for fisheries. Piscivore species are mainly made available from fisheries, and are very well paid in the market. The large catches of zooplanktivore fish, earlier used primarily for feed, are more and more used for direct human consumption. This has affected the conditions for mariculture developments negatively as no other ω3 rich bio-resource has been made available for fish feed. Mariculture development has therefore been most successful for macro-algae, herbivore animals, e.g. mussels and tilapia, and species that can be produced with a high fraction of oils and protein from agriculture (e.g. ω3 rich oils from linseed and olive) and only minor amounts of marine feed. These are all low-price species. The global mariculture production by 2050 is 50 million tonnes. The total global marine harvest (i.e. the sum of fisheries and mariculture) is 170 million tonnes, corresponding to an increase of 1.2% per year from 2000 to 2050. The perspectives for the future are negative; over-fishing is still a severe problem, development in mariculture is slow and the sea contributes less per capita to human food supply than in the year 2000. Scenario 2: Feed resources for mariculture is obtained by harvesting large herbivore zooplankton stocks Methods for harvesting and managing large herbivore zooplankton became developed by 2015, and the global harvest of fisheries in 2050 is 190 million tonnes, of which 80 million tonnes is herbivore zooplankton. This implies a major change in harvesting strategies made possible thanks to a better understanding of the marine ecosystem,


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efficient harvesting technology for large herbivore zooplankton, and new efficient international regulations and management principles of fisheries. Harvesting of fish is to a great extent directed against the large zooplanktivore stocks that are well paid because they are used directly for human consumption to greater extent than earlier. Piscivore species are less abundant in catches; they are paid an acceptable price, but these types of species are mainly produced in mariculture. Zooplankton is the main feed resource and cultured piscivores, including salmonids, are in fact now produced at a lower trophic level in culture than in nature, because their feed is based on herbivore zooplankton. The use of zooplankton for fish feed has released the fishing pressure somewhat on most zooplanktivore stocks, and management is more optimal. This positive effect on the stocks is considered to be more substantial than the negative effect of harvesting a part of their food. A great variety of species is produced in mariculture, including macro-algae, herbivore animal species (e.g. mussels) and fish. A few major species are responsible for the main volume produced, and large international companies are responsible for the majority of this production. The diversity of cultured “herb species” is still high thanks to local priorities, and smaller producers undertake most of this production. Feed of agricultural origin is mainly used for species that can be grown on such feeds. The ecological efficiency is far higher in culture than in nature, and this contributes to a total global mariculture production by 2050 of 80 million tonnes, with a high component of high priced species. The total global marine harvest (i.e. the sum of fisheries and mariculture) is 270 million tonnes, corresponding to an increase of 3.2% per year from 2000 to 2050. Future perspectives are positive, but there has for long time been a growing international concern about the carrying capacity of the zooplankton stocks. Fisheries and aquaculture contributes more per capita to the human food supply than in the year 2000. Scenario 3: Equal to Scenario 2, but a new feed resource was made available The development is identical to that of Scenario 2 up to 2030, when a new cheap source of marine ω3 rich lipids and proteins (ω3-bio-protein) coming from genetically modified organisms, becomes available as a feed for mariculture. A couple of organism that are nutritionally optimal food for marine animals have been designed and are now produced in the way that yeast is produced today. Genetically modified organisms have accordingly become accepted worldwide for use as animal food. This happened after strong pressure from the market and serious human health considerations. The ω3-bio-protein was initially used as a supplement to the established marine and agricultural resources, but became gradually cheaper and more dominant compared to the other resources. The total global marine harvest (i.e. the sum of fisheries and mariculture) is identical to those of Scenario 2, but the future perspectives are far more positive. Humans have the technology that allows an almost infinite seafood production based on cheap sugars, or, more important, methane derived from human wastes and from mineral oil and gas. Mariculture has great potential for further developments. Glossary DHA: Docosahexaenoic acid, important long chain ω3 fatty acid with

22 carbon and 6 double bonds (22 6 ω3), only present in high amounts in marine/aquatic algae and animals. Main component


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of neural tissues. EPA: Eicosapentaenoic acid, important long chain ω3 fatty acid with

20 carbon and 5 double bonds (20 5 ω3), only present in high amounts in marine/aquatic algae and animals.

Extensive mariculture:

Mariculture in open locations with efficiencies not much higher than the limits of natural marine systems, normally without addition of feed (e.g. sea ranching).

FAO: Food and Agriculture Organization of the United Nations. Herbivore species: Animals that feed primarily on plants, i.e., phytoplankton and

macro-algae. (trophic level ≥ 2, trophic level = 2 if they feed only plants).

Intensive mariculture:

Mariculture in closed and well controllable systems with efficiencies far above the limits of natural marine systems, with addition of feed (e.g., salmon cultures).

Mariculture: Cultivation of marine organisms in marine and brackish waters, methods ranging from sea ranching to intensive culture maintained in high densities under strict control.

Marine harvest: Biological resources harvested through traditional fishery activities.

Omega (ω)3 fatty acids:

Family of fatty acids that have the first double bond between the C3 and C4 positions from the methyl end of the fatty acid. These fatty acids are essential for all animals, meaning that they must be supplied in the food.

Piscivore species: Animals that primarily feed on fin fish and cephalopods (trophic level ≥ 4, trophic level = 4 if they feed on other organisms that have exploited herbivore animals, also termed 2nd carnivores).

Sea ranching: Mariculture based on release of juveniles (with optional improvements of habitat) that feed and grow in the open sea before being harvested. Sea ranching is extensive mariculture that involves low intervention with nature (juveniles are normally produced in intensive cultures).

Total marine harvest:

The total biological resources harvested through traditional fishery and mariculture activities.

Trolling lines: Lines used for the process of towing baited hooks or lures behind a vessel.

Trophic level: The group of organisms that exploit the same type of organisms as food (i.e. the same trophic level as food).

Zoobenthivore species:

Animals that primarily feed on benthic animals (trophic level ≥ 3, trophic level = 3 if they feed only herbivore animals, also termed 1st carnivores).

Zooplanktivore species:

Animals that primarily feed on zooplankton, including early stages of fish and jellyfish (trophic level ≥ 3, trophic level = 3 if they feed only herbivore animals, also termed 1st carnivores).

Bibliography Caddy J.F. and Garibaldi L. (2000). Apparent changes in the trophic composition of world marine harvests: the perspective from the FAO capture database. Ocean & Coastal Management 43, 615-655.


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[This presents development of catches of four trophic groups in FAO Fishing Areas during 1950-99 and evaluates among others the causes of the reduced trophic level of the global catches].

Candow, J.E. (ed.). How deep is the ocean? Historical essays on Canadian Atlantic fisheries, ISBN 0 920336-86-8. [This describes the development of the Canadian Atlantic fisheries].

Crawford M.A. (1992). The role of dietary fatty-acids in biology - their place in the evolution of the human brain. Nutrition Reviews 50, 3-11. [This presents theories concerning the importance of marine fatty acids for human brain development during evolution].

Hutchings, L. and Field. J. G. (1997). Biological oceanography in South Africa, 1896-1996: Observations, mechanisms, monitoring and modelling. Transactions of the Royal Society of South Africa 52, 81-120. [This characterises the production system of a famous coastal upwelling system with very high fish yields].

Kurlansky, M. Cod. A bibliography of the fish that changed the world. 1999. Vintage Random House, London. ISBN 0 09 926870 1. [This presents the history of the great cultural and economic impacts that cod fisheries had in many Atlantic countries].

Morgan, E. 1974. The descent of woman. Gorgi Books, Transworld Publishers Ltd., Earling, London, W.5., ISBN 0 552 09495 1. [This book describes in a popular way the theories of the marine phase of human evolution].

Olsen, Y., Bøckmann T., Bokn T., Bremdal S., Hoell E., Øiestad V., Skjoldal H. R., Svendsen E. and Vadstein O. 2001. MARICULT Research Programme (1996-2000). Final Scientific and Management Report from the Steering Committee. ISBN: 82-996202-0-1, pp. 32. [This is the final report from a Norwegian/European research programme that evaluate possibilities and constraints of harvesting more resources from the ocean].

Pauly D. (1996). One hundred million tonnes of fish, and fisheries research. Fisheries Research 25, 25-38. [This reviews and evaluates estimates made for the global potential of fish harvesting].

Pauly D., Christensen V., Dalsgaard J., Froese R, and. Torres F. Jr. (1998). Fishing down marine food webs. Science 279, 860-863. [This claims that the lower trophic level of the global catches is due to over-fishing of piscivore stocks].

Ryther J.H. (1969). Photosynthesis and fish production in the sea. Science 166, 72-76. [This presents a classical theoretical evaluation of the production yields of the ocean].

von Brandt, A. Fish catching methods of the world. 3rd edition, 1984. Fishing News Books, Farnham, England. [This presents an overview of methods and principles of fishing]. Biographical Sketches Yngvar Olsen was born in Sandnes, Norway, in November 1953. He is a biologist with master thesis from the University of Bergen and doctoral thesis from the Norwegian University of Science and Technology (NTNU), Trondheim. He currently works as a professor at NTNU in Trondheim and as a scientific adviser in SINTEF Fisheries and Aquaculture. In his university, he is involved in research and teaching in plankton ecology and marine aquaculture, and he was the Program Manager of MARICULT Research Programme (1996-2000,) with the ultimate aim of identifying possibilities and constraints of harvesting more resources from the ocean. Beside this, he has chaired a number of large national and international research projects in the field of mariculture and coastal sciences, and has published a number of papers in international journals and taken part in the organization of many international conferences. Anders Endal was born in Trondheim, Norway, in December 1961. He is a Naval Architect from the Norwegian University of Science and Technology, (NTNU) Trondheim. Professionally, his life was at the outset dedicated to the industrial design of fishing vessels and fishery technology and later on to research, development and education in the field of fisheries and aqua-culture. He has an extensive design and engineering background at home and abroad, as well as managerial experience from shipbuilding, consulting, marketing and research. He was a member of the UN Expert Committee on the Future of Fisheries in 1994. In 1978 he became adjunct professor at the College of Fisheries, Tromsoe, Norway,


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and since 1988 professor at NTNU, where he was Dean of the Faculty of Marine Technology (1992-1998). He has been manager and participant in national and international research programs. To cite this chapter Y. Olsen, A. Endal, (2004), HARVESTING THE OCEAN, in Marine Ecology, [Eds. Carlos M. Duarte, and Antonio Lot], in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford ,UK, [http://www.eolss.net]


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