Trawling. Silent Annihilation

Trawling. Silent Annihilation

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By Dr. Marcos Sommer

In the last 12 years, numerous fishing fleets, faced with declining most commercial stocks, have turned their gaze to deep-sea species. Only longer bottom trawls were needed, without raising the question of their management on the seabed.

* In 1843, the existence of life below 510 meters was denied and it was observed that the number of species decreased with increasing depth, for which the resutted were extrapolated, concluding that there could be no life below that already mentioned isobath
* Bottom Trawling is the least selective industrial fishing method that is still practiced in these times. Destroy funds and benthic communities.
* The benthos of the aquatic abyss also known as benthos of the bathyal, abyssal and hadal zone (200-11,000 meters), is one of the most amazing examples of survival of organisms; the life found in these places is surprisingly adapted: to pressure, to darkness, to the lack of oxygen, to the scarcity of food, to the low temperatures that oscillate between 5 and 1ºC.

In the last 12 years, numerous fishing fleets, faced with declining most commercial stocks, have turned their gaze to deep-sea species. Only longer bottom trawls were necessary, otherwise more or less the same technique was used as for traditional species, without raising the question of their management on the seabed.

In 1843 the existence of life below 510 meters was denied and it was observed that the number of species decreased with increasing depth, for which the results were extrapolated, concluding that there could be no life below the aforementioned isobath. For 25 years this position was accepted as a dogma, despite the fact that researchers of different nationalities had observed samples of beings in greater depths.

The famous Challenger expedition (1872-76), conclusively proved that there was life up to 5,000 meters deep. Animals that live in the so-called afital zone (there is no plant life), occupy 92 percent of the bottom of the oceans. This marine ecosystem is determined by the most extreme conditions of pressure and temperature that are not found anywhere else on the globe.

The "Galathea" expedition (Copenhagen) was the one that obtained for the first time samples from the greatest depths (10,700 m). Subsequent work on board the French bathyscaphe and the Russian and American ships have made it possible to repeat the sampling at great depths.

Bottom Trawling is the least selective industrial fishing method that is still practiced these days. It destroys bottoms and benthic communities, is not very selective and captures fish that live on or near the bottom. There are two broad categories of trawl nets, bottom gears for capturing different types of bottom species (shrimp, Norway lobster, flatfish), and demersal gear (cod, hake, etc.) and pelagic gears for capturing species. surface or between two waters (sardines, horse mackerel, snook, etc.).

There is still a long way to go until the exploitation of fishery resources is sustainable and respectful of the marine environment, as advocated in many international and regional agreements (International Conference on the Biosphere, Paris 1968 and the United Nations Conference on the Environment. Human, Stockholm 1972). And time is short, since for the first time in history, the main source of food is threatened in many regions of the earth and the state of fishery resources on a global scale is worrying. The fishery resources of the oceans have not yet been depleted but the future prospects are not encouraging.

To make a significant change in human relations with the marine environment, it would be necessary to transform the techno-productive system of society, as well as implement an environmental culture, a difficult task to do. Global Environmental Policy was the main theme of the World Summit on Sustainable Development known as Rio + 10, held in Johannesburg in 2002, where world leaders met to evaluate and plan the model of Sustainable Development and management of natural resources during the next ten years. In the marine field, the convention on the Law of the Sea carried out in Jamaica in 1982 should also be considered as: "One of the most important legal instruments of the 20th century", the Convention innovated in the area of ​​international treaty law. Conceived as a whole, recognizing that all the problems of the ocean space are closely related to each other and must be considered together, it established that the seabed and ocean and its subsoil beyond the limits of national jurisdiction are the common heritage of humanity, that everyone has the right to use and the obligation to protect. In addition, it provided for the mandatory settlement of disputes, established the global legal framework for all activities carried out in the oceans and seas and contained detailed rules governing all uses of the oceans and defined the rights and responsibilities of the oceans. State. Multiple global and state strategies and policies are currently derived from the Convention of the Sea for the care, preservation of legislation and development in all aspects of the maritime sector.

The main cause of fishing overexploitation lies in the excess capacity of fishing fleets, which puts excessive pressure on dwindling resources. Too many boats and too few fish, almost 50 percent of the species are endangered, and the rest would be at a level of stock uncertainty.

The problem is not only overfishing, but also that modern fishing methods are destructive. More powerful engines, more accurate cartography, satellite navigation (GPS) and location of schools of fish (echo sounders), stronger and lighter synthetic materials in the manufacture of nets.

In 2001 the bottom trawl fleet caught between 170,000 and 215,000 metric tons of fish worldwide. This represents just 0.2 / 0.25 percent of the 84 million tonnes of fish caught in the world that same year. Most of the deep-sea fishing is sold in the markets of the European Union, USA and Japan, which makes it possible to affirm that the fisheries dedicated to bottom trawling do not contribute at all to world food safety.

The bottom trawl has a diameter of around 100 to 170 meters and consists mainly of a bag-shaped net, it is the equipment used to sweep the bottom of the sea in order to extract fish that live there, it can devastate communities of marine worms, sponges, urchins, sea turtles, and other non-target species, as the net is traced with weights and steel balls (1 m in diameter) through sediments and scraped off the surface of the rocks. The mouth of the trawl is open thanks to two steel plate doors, each weighing five tonnes. The damage that is caused to the inhabitants of the bottom (benthos) of the sea can be either superficial and last only a few weeks, or intense and with impacts of decades or even centuries of duration on corals, sponges and other organisms of long life. It has also been discovered that this drag system can change the structures and sizes of the animals that inhabit the seabed.

Many benthic organisms that live buried in the sand alter their way of recycling the sediment since this fishing alters the chemical gradient of the sediments, thus reducing the productivity of the communities. Since species that live in the depths of the sea tend to grow more slowly than those that live in shallower waters, the long-term impact of trawling is magnified when practiced in ever deeper areas.

Currently an estimated 3.1 million vessels are fishing in the world, only between 100 and 300 at most are developing the technique of trawling on the high seas. Only a handful of countries have trawling fleets. Those that stand out as the most active: Russia and New Zealand, but they also include Spain, Portugal, Norway, Estonia, Denmark, Lithuania, France, Iceland and Latvia. In 2001, these 11 countries accounted for approximately 95 percent of the abyssal catches with trawl nets, although they are forced to travel long distances to carry out their activity. To catch a ton of fish a boat needs 2.3 tonnes of fuel.

The countries that make up the EU in 2001, caught 60 percent of bottom trawling on the high seas. Spain represented around two-thirds of what was caught in the EU, that is, 40 percent of what was caught in the world by the fleets dedicated to bottom trawling on the high seas.

Biodiversity studies have revealed that human activities exert a marked influence on the decrease in the number of species, on the size and genetic variability of wild marine populations in the irreversible loss of habitats and ecosystems. Thus, while many species decrease in abundance and distribution, others increase their population explosively until they become, in some cases, pests.
Fish populations are shrinking dramatically, with consequences for biodiversity. This biodiversity crisis is caused by:

1 Overexploitation by man, including legal activities (such as BOTTOM TRUCK FISHING).
2 Destruction of habitats caused by various productive activities.
3 The negative effects of interactions with natural enemies (ballast water).
4 Pollution (fertilizers, fumicides etc.).
5 Due to natural catastrophes.

The FONDO system is only about 3.7 km, on average, from the earth's surface, it is just beginning to be studied and it goes from the rupture of the continental shelf (200 m), to the maximum depth (11,000 m); include the slope and elevation of the continental margin, high seas basins and plains, submarine trenches, reef systems located in the middle of the ocean, smaller reef systems, seamounts, plateaus and other formations submarines that rise from the ocean floor.

Relatively little is known about this ecosystem, a series of devastating human activities already threaten its existence.

The main one among them is bottom trawling. The coastal fisheries are disappearing, trawlers are already operating in areas up to two kilometers deep thanks to the use of new technologies.

Bathymetric studies indicate the existence of four important features of the seabed:

1 Large, relatively flat areas covering most of the bottom at depths of 2 to 6 km, called abyssal plains.
2 Deep elongated depressions, called ocean trenches, which reach great depths.
3 Huge, very extensive mountain ranges, called oceanic ridges.
4 Large fracture zones separating sections of mountain ranges.

The transitions between the different zones are fluid: the eulitoral and sub-littoral zones are marked by the tides and the location of the edge of the continental shelf, the bathyal zone includes the continental slope, the abyssal zone encompasses the foot of the continental slope, the abyssal plains and the ocean ridges. The hadal zone includes the trenches below 6,000 meters. The abyss are generally immense flat-bottomed basins and abyssal trenches, which form the deepest regions of the ocean, between 1,000 and 11,000 meters deep.

Less than 1 percent of the seamounts present in all the world's oceans have been subjected to exhaustive biological sampling; This small percentage, however, has been enough to show that these mountains are home to a high number of endemic species, and that, together with coral reefs, seamounts constitute one of the largest reserves of biodiversity in the oceans. In fact, scientists have calculated that 100 million species can inhabit deep waters - this constitutes a biodiversity comparable to the richest tropical rainforests in the world. There are 30,000 to 100,000 seamounts

In the FONDO ecosystem the living conditions are very uniform: the temperature varies overall between 5 and 1 degree Celsius, but locally it is very stable; there is no sunlight or seasons of the year and the variations in the properties of the water are insignificant, there is no presence of oxygen and the pressure is immense.

In general, the benthos is the set of those animals and plants associated with the sea floor; that is to say, benthic are all the species that live an intimate relationship with the seabed, this as a great ecological community, extends in the sea from the shore line, to the highest depths.

The benthos of the aquatic abysses also known as benthos of the bathyal, abyssal and hadal zone, is one of the most amazing examples of survival of organisms; the life found in these places is surprisingly adapted: to pressure, to darkness, to the lack of oxygen, to the scarcity of food, to the low temperatures that oscillate between 5 and 1ºC. Furthermore organisms are peculiar in many respects: in the lack of bright colors; in the reduction of the eyes, often total blindness; They are often found in these beings highly developed tactile appendages, whether antennae or bristles in crustaceans, fin rays in some fish or cephalic extensions in others, the latter may possess - especially when they are bathypelagic - luminous organs of interesting functioning ; animals have weakness in their skeletal formation, for example: some echinoids have thin plates that are not welded together, but joined by membranous regions; crustaceans and mollusks have very thin and little calcified exoskeletons; and even fish have a weak endoskeleton. This is interpreted as a consequence of slow metabolism, which makes it difficult to fix calcium; from the scarcity of this same element in the depths, and even from a lack of vitamin D, especially in the case of fish.

Gigantism is also a frequent characteristic among deep benthic animals, a fact that has not been explained in a satisfactory way. The largest crustaceans-decapods (for example: Geryon), isopods (Bathynomus), Pycnogonida (Coloss endeis) and the echinoid (Hygrosoma hoplacanthus) can be found in the afital system, list to which several other groups could be added.
Although the biomass index is practically zero, its contributions to biodiversity are significant in terms of the variety of species present in it since many of the organisms that inhabit these abysses are unique among them and are not present in any other region. geography of the Earth. (They are endemic species of the marine abyss).

As the deep zone lacks sunlight, the food supply is necessarily allochthonous (it comes from places other than the place of life). The most abundant biomass in the abyss are bacteria, a part is chemosynthetic autotrophs, which cover their carbon needs, at the expense of the bicarbonate ion, oxidizing ammonia, hydrogen, nitrite, methane or inorganic substances. Bacteria are practically the only producers below the illuminated region. Other bacteria, heterotrophic, are nourished at the expense of the dissolved organic mass provided by the circulating water, as well as all kinds of corpses and excretions. The representation of the animal world is much broader. It includes various forms of rhizopods and a great variety of sponges, among which the hexaltinellids are especially characteristic. Among the coelenterates are hydrozoans, such as large solitary polyps, pennatulars and actinias. 375 species of echinoderms have been found below 2000 meters. Bryozoans are rare, some polychaete annelids are found, and branchiopods are found in remarkable numbers. There are also a large number of crustaceans.

Deep cold-water reefs are made up of corals, which are very primitive marine invertebrates belonging to the group of coelenterates, growing slowly - only one-tenth the growth rate of tropical warm-water corals - and beautifully constructed, but of very fragile way - three-dimensional structures, which are particularly vulnerable to impacts, such as damage from trawls on the high seas. Some corals in the eastern Atlantic have already been destroyed, and many others show marks from bottom trawling.

Some species of coral contain anti-inflammatory compounds from the pseudopterosm group. Sea fans contain concentrations of prostaglandins, compounds used to treat asthma and heart disease. Deep-sea sponges are powerful immunosuppressants and anticancer agents.

The growth structure of the corals is also the cause of the formation of islands, the Great Australian Barrier, or the Roques of Venezuela and they have cemented all the atolls of our planet, as well as the production of sand.

Cold-water corals are part of a group of organisms known as Cnidaria, which means stinging nettles and includes anemones and sea feathers. They are closely related to the species that make up reefs in warm tropical waters. They usually live in large colonies that group numerous organisms called polyps, which have eight or six tentacles that allow them to capture their small prey.
These corals are inhabitants of darkness, they feed on plankton and other organic matter. They do not possess symbiotic algae as their counterparts live in shallow, sunlit waters. Compared to more than 700 species of warmwater corals, there are only six primary coldwater reef-building corals.

The natural carpet of corals, sponges and other organisms are the cradle for young fish and areas that serve for feeding, reproducing and spawning thousands of species.

Radiocarbon data indicates that many cold-water coral reefs are up to 8,000 years old, and the oldest and tallest ever observed reaches 35 meters in height. Geological records date back millions of years. Crustaceans, fish, urchins and starfish are part of a diverse community that contributes to cold-water coral reefs. Some countries, including Norway, Ireland, the United Kingdom, and the United States, have in recent years placed some of their cold-water corals under extreme protection, including designating them as Special Conservation Areas or Habitat Areas of Particular Concern.

It is crucial that corals are given protection as they grow slowly - only one-tenth the average for warm-water corals - and are home to thousands of other species, including numerous commercial fish populations. This important web of life is more fragile in structure and for this reason they are particularly vulnerable to impacts such as damage caused by deep-sea bottom trawling, targeting the deep habitats and surrounding waters.

Trawling, as it is called around the world, must be compared to "rake fishing" that is constantly evolving. In the past two boats dragged the heavy nets. Today only one boat does the job, thus maximizing the fishing effort and therefore more vessels are made available to sweep the seabed. Currently the nets can reach up to 2 kilometers deep devastating fragile coral reefs and rocky bottoms. This is how the destruction of the habitats of the sea floor is one of the main factors in the reduction of the existence of fish in areas where trawling is excessive.

According to a global calculation, the area where trawling occurs covers 14.8 million square kilometers of the seabed. In other words, the area of ​​the seabed affected by trawling is 150 times the area of ​​land with forests that is logged annually.

Many of the species of fish that inhabit and around cold-water corals and seamounts also grow slowly and have lower reproduction rates than species that inhabit shallower depths, such as herring and cod. These deep-sea fish, which include blue ling, orange roughy, mirror dory, grenadier (rat of the seas), silver San Pedro, alfonsino, monkfish, ochavo, blue-eyed trevalla , the black saber and some deep-sea sharks are increasingly targeted as boats shift from traditional, well-worn fishing waters to deeper ones. This means that recovering from overfishing is not easy for these fish stocks, and many deep-sea fisheries have been overexploited in less than 10 years.

The concentrations of these fish around seamounts and corals - either for food or for spawning - have made them very attractive fishing grounds. However, studies show that the long life cycles and slow sexual maturation of deep-water fish make them particularly vulnerable to large-scale trawling activities.

It should be noted that fish such as the Orange Clock (Hoplostethus atlanticus), the one of most interest due to its white and firm flesh, of excellent keeping capacity that has a flavor similar to shellfish and is priced in the market at figures close to 23 per kilo. In France it is usually presented for consumption in fillets, orange roughy has also gradually conquered the Spanish and German markets where it comes to replace traditional white fish in prepared dishes without great difficulty.

This carnivorous species, discovered in New Zealand waters in the late 1970s, is threatened by overfishing. An adult specimen can reach 70 cm in length and can live up to 150 years and reproduces from 30 years. During the spawning season they are found in large concentrations which makes them very vulnerable to fishing boats, as confirmed by the record of 70 tonnes of Orange Clock caught in New Zealand in a single fishing set. The pattern that these fisheries follow is that of rapid development with large catches at the beginning, followed by a decrease in the abundance of the stock and in the levels of capture until reaching a level of overexploitation and the collapse of the resource in a few years. The exploitation of this species began without there being reliable scientific data - these deep ocean bottom fish have been little studied, and until not long ago fishermen returned them to the sea.

In bottom trawling, the high rate of incidental or unintended capture also stands out, which includes a large amount and diversity of marine life among fish, crustaceans, mollusks, mammals and birds with no commercial value or with juvenile characteristics that cannot be introduced. to the markets and is discarded or returned to the sea where most die from injuries or have been out of their environment. Fisheries experts estimate that bycatch amounts to about 25 percent of the world's marine fisheries, that is, about 20 million metric tons by the UN Food and Agriculture Organization (FAO 2004). describes that currently the world fishing fleet dumps some 7.3 million tons of discarded fish into the sea every year, a volume that has been reduced since the mid-nineties, it is not known, at the moment, if this is a positive or negative data . Indeed, the reduction in the volume of waste could simply be due to the depletion of fishing grounds, since in many regions fishing has already reached the maximum possible limits of sustainability.

FAO acknowledges that in some countries measures to reduce accidental catches in certain types of fisheries have come into force, making it much easier for boats to avoid catching unwanted species. But also the fish that until recently would have been thrown into the sea as waste is now kept on board and used.

The difficult thing is to know if the greater selectivity is the cause that almost twelve million tons less are discarded or if this fact is due to the fact that the processing has improved a lot and the proportion of harvested catches is now greater. The problem is that this increased use could actually be hiding a worrying fact: boats are taking more advantage because catches of traditional species are declining. In fact, having less fish discarded, the logical thing would be to hope that the level of catches had increased, but it has not been like that: catches on a global scale have remained stable.

In certain fisheries, bycatch exceeds target varieties. For example, in the case of shrimp catches, discards may exceed the volume that is extracted in a ratio of 5 to 1. In a study in the South Atlantic (Argentina), the tango fleet during the first four months of 2002 returned to the sea. 18 thousand tons of hake and 25 percent of the shrimp caught for not reaching commercial sizes. In the north of the Tyrrhenian Sea, trawlers discard 34 percent of hake, 41 percent of the sachets caught of cod. In the North Sea, 90 percent of the juvenile cod that would have to grow and reproduce to replenish stocks in 1996 were caught and discarded.
According to the United Nations Environment Program, trawling in the Aleutian Islands, Alaska, between 1990 and 2004 "incidentally" captured more than 2 million kilograms of corals and sponges.

At the beginning of this century there is a great lack of information and basic scientific opinions. Many components are unknown, which undoubtedly would offer a better understanding of ecosystems. The scientific community must therefore modify its way of treating existing problems, but at the same time it is necessary to give it the means to do so, since there is a great lack of tools, indicators and methods for evaluating the richness of resources. the ecosystems. A scale of key ecosystems would also allow us to see the issue more clearly. The logic of the system is complex, but what we can say is that everything is interrelated, everything is interdependent. The quantification by species, which is carried out mainly after landings, does not give us an exact measure of reality. This is because part of the information needed to know it is missing, since a species is never isolated. Thus, for example, a marine ecosystem includes, in addition to fishing resources, benthos, birds, whales, etc. It is necessary to protect the whole complex, mainly through the delimitation of marine protected areas. It is completely absurd to try to separate a species from the environment to which it is attached. The fish is a resource that has its own behavior, that moves, that evolves according to its specific ecosystem. There is no doubt that even the fisherman must be integrated into the study of ecosystems. In order to provide an adequate response to all the problems that arise, it is necessary to have a variety of approaches.

Protecting biodiversity and knowing your environment is like making an insurance policy. The greater the diversity, the greater the means we have to cope with natural evolutions in the long term, such as climate change, or in the short term, such as catastrophes. Excessive predator capture simplifies ecosystems. At present we are verifying that there are more and more invertebrates such as shrimp and squid. Biodiversity is also a common good, since the sea belongs to citizens, fish, sailing enthusiasts, etc. We have an obligation to protect it for future generations. Fishing cannot be isolated from the rest either, since it depends on the climate and the seabed. Protecting biodiversity does not require radical change, but many small actions in various directions.

Finally, citizens in general must understand that they have a great role to play in the protection of biodiversity, of which they are also an integral part. It is about their attitude towards nature, their preferences when deciding their consumption, and their way of life, which have an important influence on the long-term evolution of ecosystems. Ultimately, it is the actions of billions of people who are going to decide whether or not to conserve biodiversity.

El fondo del océano está lleno de cicatrices, algo muy preocupante, ya que es ahí donde muchas especies viven y se reproducen.
La humanidad saquea su futuro.

* Dr. Marcos Sommer

Llamado a la humanidad de apoyar a la Coalición por la Conservación de los Fondos Marinos en Aguas Internacionales (DSCC, siglas en inglés), que está llevando una campaña, en la que señala que la Pesca de Arrastre de Fondo está causando un daño sin precedentes a los frágiles ecosistemas de las profundidades marinas, la meta es conseguir que los países miembros de la Asamblea General de las Naciones Unidas voten a favor de tal moratoria (texto de la declaración sírvase ver ).

Video: The destructiveness of bottom trawling (July 2022).


  1. Terriss

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  2. Lea-Que

    Well, so-so...

  3. Sani

    the quick answer, the characteristic of the mind :)

  4. Owain

    Analogues exist?

  5. Yozshurn

    The portal is superb, however, it is noticeable that something needs to be tweaked.

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