History of fisheries

There is no doubt that, gradually, what grows and inhabits the seas and oceans will be used in Man’s diet and will become an increasingly larger part of our daily food and will receive its deserved recognition and popularity.

From ancient times, the seas and oceans were "hunting areas", in which Man caught fish and marine mammals, and on the shores, collected edible molluscs and seaweed. Gradually, boats, hunting and fishing implements were improved, increasing the scope of his food-gathering. Expanding the geography of his tool making craft, it is not an accident that many different peoples of the World settled near the Ocean.

Now, as the population of the Earth quickly grows, the biological resources of the Ocean will help to decide the most acute problem facing us: supplying the population with high-quality yields of food.

A variety of natural riches of the World Ocean can be used for public consumption without damage to the natural reproduction process.

A serving of fish in our daily diet becomes more and more popular. Fishes and other "gifts of the sea" now provide the protein needed for a balanced meal, and is third in consumption in the World, after meat and milk.

In deep waters of the seas and oceans and on the sea floor lives one of the most diverse living entities in the World, but it is very infrequently used. Many fish, invertebrates and seaweed as probable sources of food remain unexamined. In the near future, "the granary" of our planet will yield seaweed from vast and dense undersea meadows and “forests.”

The "living treasure" of Neptune’s realm is a huge basket of food supplies. But to use these riches, it is necessary to do it carefully and within reason. If the Man is to save these "living treasures," he must proceed with a rational management plan to improve artificial cultivation of marine life and to care for the cleanliness of waters, for, as have shown by recent studies, the Ocean is not always a magic, self-covering table cloth. The reserves of its livestock are not unlimited and it is impossible to say that all new habitants of the Ocean will not be on the endangered species list as found in "The Red Book". The Ocean is common property for all Mankind. Research and economic use of underwater treasures is a common business of all countries. Mankind closely looks at the Ocean, actively studies it today and awaits much from it in the future.

Fishing, hunting marine mammals and collecting seaweed, molluscs and other gifts of the sea can be traced to great antiquity, to which archaeological finds at ancient campsites of primitive people can attest. In rock carvings and images found on pottery, primitive depictions have been found showing episodes of fishing or hunting marine animals.

By the First Millennium BC., fishing had become one of the primary activities of the inhabitants of coasts and islands of the seas and oceans.

Sometimes excess fish, brought in during rich catches, became a means of exchange or trade. Gradually, new trades appeared: fisherman, hunter, preserver (salting and smoking) and shipbuilder. New trading areas were opened and established, and new settlements were established on the shores.

Fishing and hunting of marine mammals have sustained the existence of many peoples of the world and stories about these efforts are repeated in oral and written national histories (legends, songs, ritual dances).

The art of carving lines on the bones of a marine mammals arose in antiquity and a long history of development has passed. The craft has not lost the value even in the present time. Hunters of the Arctic Region, Eskimos, Evenks, Chukchis, Aleuts, Inuits etc., engage in the practice. In America, this art is called "scrimshaw".

1. Volume of fishing catch in millions of tons
2. The population of the Earth in millions of people
3. Catch per capita in kg

Presently joined with the rapid increase of the population of the Earth, there is a more acute problem: how to feed these new mouths.

Modern diversified agriculture uses a land area of 44 million km², and from it, receives more than 98% of the total volume of food, consumed by Man. The remaining 2% comes from the food harvested from "the Ocean field", which covers an area of about 360 million km². This is an impressive contrast. The results of centuries-old activities of Man, from the time when he was a hunter and gatherer of wild fruits, gradually developed into effective methods of agricultural management.

Further development and the perfecting of agricultural production will supply food to the eight billion people on the Earth (estimated by the year 2025) only by making large financial expenditures of which only a few countries of the world are capable.

There is the actual prospect of a reduction of agricultural lands due to an increase of climatic warming and a rise of the level of the World Ocean, and also a reduction caused by changing farms into industrially developed area, flooding by the creation of artificial reservoirs and by surface mining.

A solution to the problem, therefore, is seen in the rational use of the biological resources of the Ocean.

The crop of the "light-blue field" is a major source of food substances of high biological value. Proteins, fats, mineral salts, trace-elements and vitamins are a part of their structure. The greatest interest is represented by proteins, which contain all the necessary amino acids required to sustain human life. The ocean already produces 6% of all consumed proteins

Official international statistical data reports indicate that, in modern uses of the Ocean, the predominant use, 82.2%, is for fishing; 12.7% is for collecting invertebrates, 4.8% is for harvesting seaweed and the taking of all other kinds of marine life, including marine mammals comprises about 0.3%.

The use of marine provisions has increased more and more over the last few years. On the advice of the experts, the world catch should be increased by the year 2000 to up to 130 million tons per one year, which would satisfy the needs of the population.

The reserves for further expansion of the world catch of biological resources are available. However, overcoming the lack of use of some of the flora and fauna of the Ocean, decreasing the degree of pollution, implementing certain goals of science and engineering, development of mariculture and refining the legal problems with regard to exploitation and trade - these are the barriers that must be passed.

World fish catch and taking of invertebrates and seaweed in millions of tons (1971-1990)

In a single serving of a meal, the population of many countries are widely using fish and edible marine products. The consumption level of marine life on islands and in coastal nations such as Japan, Iceland, Portugal, Norway, Denmark is especially high; where each inhabitant annually consumes from 20 to 80 kg of fish and other "gifts from the sea".

The majority of the catch is sent for processing in the food industry. Since marine products are unable to be stored for long periods without special processing, they are subjected to various methods of preservation. The greatest amount of the products are given applications of low (cooling and freezing) and high temperatures (pasteurisation and sterilisation), desiccation (drying, jerking), chemically preserving the foods in salt and/or vinegar, and so on.

At the same time, huge quantities of fish go for the preparation of fishmeal and fats. The fishmeal is widely used in livestock raising, poultry farming and on breeding farms of fur-bearing animals. The Ocean biological industry also supplies raw materials for medical, perfume, microbiological and other industries.

There are still expensive problems with regard to the complex processing of raw material, reduction of losses during food production and more effective utilisation of scraps.

1. Percentage of catch used for food

2. Percentage of catch used for technical needs and fishmeal

Industries using Biological resources of the Ocean
(seaweed, fish, invertebrates, marine mammals)

Medical	Textiles
Chemicals	Paints and pigments
Perfumes	Pharmaceuticals
Farming	Paper

FERTILITY OF THE OCEAN A long history in fisheries-management shows that the sizes of catches in many respects depend on a knowledge of geography and conditions creating fertility of the Ocean.

As a result of many types of scientific activities during many expeditions, it was found that there are areas having high, middle and low amounts of productivity in the World Ocean as well as on land.

High and average productive areas, the levels at which "fertility" is comparable with productivity of arable lands, comprises about 37% of the entire water area of the World Ocean and are located in temperate, cold and shelf waters, zones of upwelling, the upper layers of water of the continental slope and on banks in the open Ocean. The most productive are waters and floor of the continental slope, which provides up to 90% of the World catch.

Low productive areas can be compared to "fertility" in deserts and cover about 63% of the water areas.

1. Low productivity provinces

2. Middle productivity provinces

3. High productivity provinces

More than 1,200 billion tons of phytoplankton, the first link of the food chain, annually grow in the Ocean. The annual crop collected by Man from the "light-blue field", is now about 85 million tons. This great difference can be explained by the fact that, between phytoplankton and fish caught by Man, other forms of life exist in the long food chain. Scientists have found, that at transition from one link in the food chain to the next, a ratio of 1:10 exists. Therefore, 1,000 kg of phytoplankton provides food for 100 kg of zooplankton, which provides food for 10 kg of small fish and to increase their weight by 1 kg, commercially-caught fish must eat 10 kg of smaller fish. These ratios suggest probable solutions for more effective utilisation of biological resources of the Ocean. One solution is to reduce the "length" of food chain links, for example, using food containing a lot of proteins not only for fish, but also for feeding zooplankton.

COMMERCIAL FISHES The development of the world fishery is, in many respects, determined by the use of the largest supplies of fish-types. From almost 15,000 species living in the World Ocean, about 1,500 species have commercial applications, but only 22 families determine general productivity of the world fishing industry: herring, cod, mackerel, anchovy, shad, smelt, tuna, hake, dab, maigre, launce, swordfish, salmon, mackerel, shrimp, shark, porgy, belted bonito, mullet, filefish, skate, lizard fish.

For many years the main catches were herring and cod. During the last few decades, however, the number of species of fish caught in commercial quantities has grown as the engineering and technology has become increasingly more efficient. In 1970, 56 species of commercial fish were taken, with a catch volume for each species at about 50,000 tons. Now, there are more than 80 species commercially fished.

A statistical analysis of the fishing industry shows that, despite an enlargement of the species caught, in the last 40 years, the main catches were of herring and cod.

Volumes of anchovy and mackerel catches have been noticeably increased. However, new species being caught include deep-water fishes (grenadier fish, red bream etc.).

The construction of new fishing trawlers capable of high-speed trawling at different depths using large volume trawls and the broad use of purse seine nets have permitted an increase in the catch of fast-swimming fishes, including mackerel and tuna.

The number of commercial species caught is significantly variable, and that has an outcome on the industry as a whole. These variations are caused by changes in living conditions, condition of natural food base, degree of water pollution and the intensity of fishing.

Herring
Cod
Mackerel
Anchovy
Horse Mackerel
Tuna
Plaice
Salmon
Saury
Bonito

GEOGRAPHY OF FISHING The distribution of fishing regions of the World Ocean depends on many factors: histories of development of the industry, population of coastal nations, usual types of meals, conditions and effectiveness of the use of biological resources and the level of development of a commercial fishing fleet. The change in zoning of world fisheries are, to a certain degree, a result of changes on the World political map and afore-mentioned factors.

Until 1938, the regions of heavy and moderate commercial fishing were in the northern part of the Atlantic and Pacific Oceans, where up to 80% of the World catch was taken. The remaining water area yielded only 20% of the catch. In later years, moderate commercial regions have developed in the southeastern parts of these oceans.

Toward the end of 1980s the share of catch in the Northern Hemisphere (north of 20°N) comprised 57%; in the tropical zone - 24%; and south of 20°S - 19% of world catch each year.

In 1991, harvesting of biological resources of the World Ocean was distributed as follows: Pacific Ocean: more than 63%, Atlantic Ocean: more than 28%, Indian Ocean: 8%

In addition to the fact that reserves of traditional populations of herring, cod, bass and anchovy were being exhausted in many regions of constant fishing, there was a the actual threat to natural reproduction and even extinction of some species.

The establishment by a majority of the coastal nations of a 200-mile fishing economic zone impedes the commercial fishing activities of other countries. This circumstances has forced the fishing industry to search for and utilise new geographic regions.. Present plans are to search the tropical waters of the World Ocean in places where there is a rich food base and accumulations of pelagic fishes have been detected. In newly developing regions, island and island nations control significant ocean areas.

The geography of the fishing industry testifies to the need for quickly developing new fishing regions and implements for fishing on nearly all areas of the World Ocean.

The annual registration and statistics of fish catches is conducted by the UN Food and Agricultural Organisation (FAO). It established commercial fisheries regions designated by numbers on the chart.

FISHING VESSELS The creation of large fishing fleets in the world began at the end of 19th century. and was fuelled by the increased necessity for inexpensive food for the developing industrial centres of Europe and North America. The then newly-built fishing vessels were equipped with steam and internal combustion engines, the fishing equipment was improved and the range of vessels increased.

Presently, the make up of a commercial fishing fleet of developed countries engaging in biological exploitation of the Ocean, depending on the assignment, are subdivided into fishing, processing and transport categories.

Auxiliary vessels engaged in the fishing industry are divided into categories: search, scientific research, educational and other. They are used for locating and types of catch, research activities, providing experts for the fishing industry and supply of fishing vessels.

Service vessels provide assistance to fishing boats in ports and are operated by commercial firms within the fishing industry.

At the beginning of 1990s, the World-wide commercial fishing fleet included almost 1 million vessels of various tonnages, engine power and fishing equipment.

The largest commercial fishing fleet is operated by Japan. Almost a third it are small-tonnage vessels engaged in collecting molluscs, other marine communities and seaweed.

The fleet of the USSR took one of the leading places in tonnage among the World commercial fishing fleet at the beginning of the 1990s. It had 2,700 fishing vessels, more than 200 floating fish-processing “factories” and more than 500 refrigerated transport vessels..

The fishing fleets of developing nations can sometimes be small sailing and rowing vessels. For example, fishing in and near India often accomplished by some 220,000 canoes, small boats and catamarans. Very few are equipped with engines.

Floating fish-processing factory ship
The floating fish-processing “factory” ship is a large tonnage vessel which processes catches brought to them by smaller fishing vessels. They also supply these vessels with fuel, food, water and fishing equipment.
On floating factory ships the final products are tinned, frozen and/or salted, depending on the species.
Productivity of factory ships ranges from 20 to 500 tons of final products per day.
The floating factories have displacements of up to 45,000 tons, lengths of up to 220m and speeds of up to 19 knots.

Medium refrigerated fishing trawler
The most widespread type of vessels in a modern fishing fleet is the trawler, a vessel which trawls on or near the sea floor for pelagic fishes, squid, krill and shrimp. In nations with a modern fishing industry the primary portion of the total catch is produced by trawling.

Seiner
A seiner is a vessel which catches fish in a purse seine-net. Trawlers and seiners are equipped with refrigeration and fish-processing machinery, and with fish-locating instruments. Fishing vessels are divided by sizes ranging from large (supervessels) of lengths of 100m and more, large, with lengths from 65 to 100m, medium, with lengths from 34 to 65m and small, with lengths from 24 up to 34m.

1. Wheelhouse/bridge
2. Trawling winches
3. Drum for pulling a trawl net
4. Trawl deck
5. Hatch through which the catch is loaded onto the processing deck
6. Fish processing machines
7. Refrigeration units for storing the cleaned fish
8. Engine-room

1 Floating nets
2 Fishing with the help of lighted floats
3 Gill-net
4 Hook tackles
5 Bottom trawl
6 Pelagic trawl
7 Fishing by purse seine net:
a - encirclement of seine;
b - Surrounding a shoal of fish;
c - laying out / retrieval of purse seine net.

Purse seine net fishing. Guiding a fishing vessel to a school of fish by aircraft.

Modern commercial fishery is conducted by diverse fishing equipment. Basic to them are the trawl, purse seine net, floating nets, hooks and tackles.

The trawl is represented by a cone-shaped net. When it is pulled through deep water (pelagic trawl) or across the bottom (bottom trawl), a shoal of fish is scooped into the mouth (forward broad part) and into a cone-shaped net. Herring, cod, marine bass, flounder, hake, and also shrimp, and squid are examples of species caught by trawls.

A purse seine net is a tackle made from netting in a rectangular or trapezoidal shape. Finding a shoal of fish, the vessel sails around it, putting out nets and thus surrounds the fish with a wall of net. Next, the bottom of the seine is drawn closed, and a huge bag (purse) is formed. The length of such a purse in a circle can reach 2,000 m and more, and extend to a depth of up to 300 m. When the seine is pulled, the top of the purse is drawn closed and the fish are then enclosed in the net purse. Black sea anchovy, some species of tunny, mackerel, anchovy and other fishes forming dense shoals in the upper layers of the water are caught by purse-seine net fishing. Purse-seine netting is one of the most productive kinds of fishing, for in one encirclement, it is possible to take several hundred tons of fish.

In the World commercial fishing industry, trawls and purse-seine nets have the widest distribution. However their application requires the installation of powerful engines for towage and production of mechanised operating systems for the descent and raising of trawls on fishing vessels.

In the last few years, trawls and purse seine nets have been equipped with electronic tranducers, which send information to a fishing vessel about the characteristics of the movement of trawls and purses at depth. The processing of this information, together with data from fisheries research, permits the guidance of a trawl on a shoal of fish.

Catching fish which do not form dense schools is conducted by the use of floating nets. Usually they are connected to one-another. So-called net orders with from 100-150 nets, reaching in length several tens of kilometres are formed. These instruments are used at shallow small depths within the limits of the continental shelf.

The value of the fish hook has not been eliminated. The primary application is between bottom of the marine seine, that is, the pelagic tier and the bottom. Pelagic tier fishing is conducted using a cable with a length of up to 150 km and more. From the horizontal cable, through approximately each 50 m vertically, hooks are placed. One tier can consist of 2,000 and more hooks. Live-baits are placed on the hooks. From the pelagic tier, large oceanic predators - tuna, marlin, swordfish and sharks are often taken. From the bottom tier, cod, herring etc. are caught. Sometimes, to increase the effectiveness of fishing by hook, sound or fragrant substances are used as additional baits.

In the Japanese fishing industry, automatic devices have been created to replace customary fishing tackle. They are mainly used in fishing for tuna..

To increase the concentration of fish, electric lights are sometimes used as bait or as floats for nets.

1. Shoal
2. Transducer
3. Towed receiver
4. Screen monitor
5. Record of fish shoals
6. Echogram

The search and detection of shoals of commercial quantities of fish is conducted by using transducers on vessels. The transmitter sends signals directed to thebottom, and measures the time the sound takes to reach the bottom and reflect back to the receiver. If a shoal of fish appears between the hull of the vessel and the bottom, this time is reduced. On a recording roll of a recorder (echogram) detected shoals are represented as dark spots. To guide a trawl to shoals, the transducer is attached to a screen monitor. Information about the position of the trawl is transmitted to the ship from a towed receiver.

Seaweed is considered to be one of the most ancient representatives of the plant world. They occupy the layers of the sea up to depths of 100 - 400m depending on a transparency of water and the lower limit of light penetration.

The various kinds of marine seaweed represent valuable food raw material used by the peoples of many countries of the world. For inhabitants of Southeast Asia the seaweed has long been a normal and essential part of a meal.

1. Africa
2. Europe
3. Americas (North and South
4. Asia

The basic commercial types of seaweed are: laminaries, coctaries, undaries, porphiras, phylophores and cystoseires. The sizeable content of vitamins, carbohydrates, proteins and trace-elements in seaweed have been used in the manufacture of medicines for a long time. Substances extracted from seaweed are used in textiles, perfumes, photographic materials and a number of other products. A considerable part of extracted seaweed goes for forage to raise cattle and for fertilisers of agricultural fields. Extraction of seaweed is conducted by special dredges and floating mowers in the coastal zone after storm or at low tides. For further processing, the collected seaweed is dried and stored under a canopy or in sheds, and some kinds of seaweed are placed on barges and flooded with a water. The annual world extraction of seaweed comes to almost 3.5 million tons.

Over the last few decades, there has been a steady increase in the use of biological resources in the Ocean, including marine invertebrates. In 1970, a little over 5 million tons were harvested. By 1986, the take was almost doubled. Organisms included in this group are squids, krill (tiny Antarctic crustaceans), and primarily, shrimps, lobsters, crayfish, crabs, oysters, mussels, clams, scallops, urchins and holothurians (sea cucumbers).

In the World harvest of invertebrates, a significant catch is Antarctic krill. From reports issued by the FAO, the 1986 krill catch was 445,000 tons. It is used in the preparation of canned food, animal fodder, flour and frozen foods.

1. Northern boundary of krill distribution

2. Basic regions of krill accumulations

Annually, large catches (on the order of 400-500 thousand tons) bring harvests of large oysters, ordinary mussels, clams and Japanese squid. Taking of pelagic invertebrates is conducted by trawls, and from the bottom, by dredges or traps. Such invertebrate species, as shrimps, oysters, mussels, crabs, lobsters and crayfish, are used for preparation of delicious dishes. In the World market of sea food, the harvest of these invertebrate species yields a significant amount of revenue.

1.Giant oyster
2.American oyster
3.Korean mussels
4.Ordinary edible mussels and clams
5.Green mussel
6.Japanese scallop
7.Magellanic scallop
8.Calico scallop

1. Oval crab
2. Swimming crab
3. Light-blue crab
4. Fiddler crab
5. Spotted crayfish
6. Norwegian lobster

HARVESTING MAMMALS The history of whaling and hunting marine mammals goes back many centuries. In the 11^th century, the harvesting of whales was conducted by Basques in the Bay of Biscay. An intensive whaling industry, which Northern countries carried out in the 17^th - 18^th centuries in northern areas of the Pacific and Atlantic Oceans, was stimulated by needs for fats (for oil), meat and especially for the famous whalebone, which went into manufacturing of crinolines, corsets, hat frames and many other items.

With the invention of a harpoon gun in the middle of the 19^th century, perfecting of instruments of harvesting and cutting up and rendering of whales, whole whaling fleets appeared and resulted in a sharp increase in the numbers taken.

By the end of 1930s, it had become obvious that the number of whales, especially blue-whales, were disastrously decreasing. Therefore, in 1937-1938, the interested countries jointly worked out agreements to regulate the whaling industry in the Antarctic region. In 1946, the International Commission on Whaling was created by an international agreement to regulate industry. But this measure could not halt the decreasing numbers of whales

Over the span of the last few decades, in many of the nations of the World, a broad movement has been organised for the protection of whales. As a result, in 1988, the whaling industry essentially ceased to exist. However, whales are still being harvested but in more limited numbers.

The harvesting of pinnipeds, that is, walruses, seals and fur-seals, over the span of centuries was actively conducted to obtain valuable fur and oil (fat). The industry took a heavy toll on the numbers of these mammals. As a result of conservation measures undertaken by the efforts of joint projects of several countries in the past 20 years, the numbers of the primary species of pinnipeds is coming back.

MARICULTURE Mariculture is the cultivation and documentation of marine seaweed, invertebrates and valuable species of fishes in conditions controlled by experts.

The history of mariculture goes back over 4 millennia in time. In Ancient Rome, grey mullet were cultivated in coastal marine lagoons. It is also known that about 4,000 years ago, the people living on the coasts of China grew fish in shallow water ponds artificially separated from the sea.

The main products of mariculture are oysters, clams, shrimps, seaweeds (laminaria, porphira, undaria), fish (salmon, sturgeon, mullet, scad, milk fish, flounder/plaice etc).

Two basic directions of development of mariculture are now in place. The first is the cultivation of fish and invertebrates, growing in artificial conditions (on fish-farms and in nurseries) until the young fish are viable and durable, and then placing them in natural reservoirs or completing the growth cycle in artificial ponds and pools with artificial food sources. The second direction is cultivation of marine organisms in their natural environment in coastal marine water areas, bays and gulfs that are separated from the sea by nets.

1. Cultivation of durable young fish
2. Release after fattening
3. Industry
4. Commodity output

In mariculture facilities of this type fish roe or larvae of invertebrates are nurtured in nurseries on artificial foods. When they can survive, they are release into the sea for fattening and subsequent fishing. This type of mariculture applies to the cultivation of salmon and milkfish.

1. Durable young fish
2. Cultivation up to documentary sizes
3. Commodity output

In mariculture facilities durable young fishes are grown in coast fish-ponds, and then transfer in floating or submersible fish-ponds, where it reaches documentary sizes.

1. Young fish
2. Cultivation up to documentary sizes
3. Fish-pond
4. Commodity output

The perfect type of mariculture consists of cultivation of marine organisms up to documentary sizes in natural conditions in closed off embayments, or in parts of the sea fenced in by nets.

In 1985, the world volume of production in mariculture facilities produced about 5.5 million tons, predominantly, molluscs (3 million tons) and seaweed (2 million tons). Fish make up only a very small part (500,000 tons).

The long-term experience of management of mariculture is held in Japan, China, France, Italy, Norway and Great Britain. To some extent, the practice of mariculture is used in the majority of the coastal states.

In Russia, experimental activities on the cultivation of molluscs and seaweed are conducted in Barents, the White and Black Seas, and the Sea of Japan.

The implementation of principles and methods of molecular biology and genetics in the near future can be used to create new species of valuable fishes.

English investigators have developed a way of obtaining of diploid (all female) young flounder.

A new type of marine cabbage giving a production yield 20% higher than natural kinds has been developed in China as a result of selection experiments.

Scientists consider that the hybrids of marine plants will have tastes similar to those of natural fruits and vegetables that people normally consume.

1. Areas of introduction of Pacific Ocean salmon
2. Areas of salmon distribution
3. Areas of mass approaches of salmon for spawning
4. Area of distribution of milk fishes

Mariculture includes also a realisation of measures for the resettlement and acclimatisation of valuable marketable fishes or invertebrates from their normal habitats to other regions with similar physical-geographical conditions.

In Russia, resettlement and acclimatisation efforts of Pacific Ocean salmon are being carried out in the waters of the Barents Sea. The resettlement of valuable commercial species of the tropical waters of the Indian Ocean (milk fish) in Pacific Ocean coastal waters on the west coast of the USA is presently underway. After a few decades, these efforts have produced commercially productive stocks..

In many respects, the successful development of mariculture depends on the knowledge of the Ocean environment in the waters and on the bottom, and the biology of the cultivated organisms.

The increased effectiveness of mariculture has been promoted by the creation of artificial reefs on the bottom, for which old marine construction vehicles, old automobile bodies, and even scrapped aircraft fuselages are being used. On their surfaces, seaweed develops, which, in turn, creates favourable conditions for fish spawning, and reliable shelter for young fish.