I. Akimushkin. Chimeras. The all-devouring jaws. All life in movement. Embryonal cainism. The march-strike of the 'red' fish. Light and vision. Archers and spearmen. The piranhas. Lungfish. Tailed amphibians
The second subclass of cartilaginous fish, the Holocephali, unites sea fish with strange appearances and anatomy, which unite in their person some traits of bony and cartilaginous fish, and therefore they are called chimeras. (Thus, the ancient Greeks named magical monsters that were composed from parts of various animals. An example of a typical chimera is the Sphinx). The up-per jaw is fused to the jaw, (hence - the 'Holocephali', 'complete heads'). The chord is retained for the entire life. The teeth, as in the case of lungfish, have fused into plates that grind food. The dorsal fin has a venomous spine, which can be dangerous for humans. The tail fins of many chimeras are elongated into long cords, similar to rat-tails, hence anglers name those fish 'the rat-fish'. Males develop special 'clasps' on their heads and bellies - outgrowths with hooks and spikes, with which they hold the females during copulation. Often the chimeras lay only two large eggs, encased into firm horny shell, as sharks and skates do.
Around 30 species in live in all, except for the polar, ocean waters, (one specie - in the Mediterranean Sea as well), in shallows and in depths. They feed mainly on crustaceans, molluscs, echinoderms. The meat of chimeras is eaten in some countries, but usually in medicine, and also in lubrication of tools and weapons, the liver fat is used, since in some species the liver weights about one-third of the entire fish in question. The chimeras' sizes vary from 0.5 to 2 m.
THE ALL-DEVOURING JAWS
Like grey ghosts, they appear in the blue murk, suddenly appearing from somewhere, where 'the wondrous shade of the sea lies'. Now, seemingly unwilling, they lazily circle: ever narrower, ever closer. As if, the designated victim is not even interesting to them - and suddenly... Water foams and colored with blood. The strike of an attacking shark is faster than eye can see. The first shark is followed by a second, a third... All of them, no matter how many there are, crazily tear up the sea turtle, dolphin, wounded whale, human - anyone, who was fallen victim to them.
'Only several feet separated us from this saturnalia and we excellently saw how a shark bites. It happened that the predator always turned upside down to bite. However, this was not always so. We saw them swim at the prey directly and opened the jaws, bending their nose upwards at a sharp angle. The trap, full of sharp teeth, was forwards. The shark bit the whale's side, closed its' jaws and its entire body shook, as if in convulsions: the carnivore used its teeth as if they were a saw. A moment - a bite is sawn-off; the shark swam a whale, and in the whale's side a pit with even sides shone' (J.-Y. Cousteau, Z Dagen).
Aboard the transporting ship 'Cape San-Juan', torpedoed by the Japanese, were 1429 people. Only 448 were saved.
'And even during the rescue operation several flocks of sharks continued to frenzy among the inflatable rafts and destroy those, who were upon them...
Again and against the soldiers' cries sounded while the sharks pulled them from the rafts into water. Sometimes the sharks attacked those people, who were dragged to the ships on rescue ropes' (G. McCormick, T. Allen, V. Young).
The transporting ship 'Nova Scotia' was sunk at the shores of South-East Africa, a thousand people have died. Around floated numerous corpses in inflatable vests, 'all bodies were legless'.
The ended war brought rich pickings for sharks of all kinds and even the HQ officers understood, how dangerous the sharks were for soldiers, marines and pilots, trapped in the tropics. Yet at the beginning of the war itself in the 'Manual for shipwreck survivors', released in USA, this was written: sharks are 'slow, cowardly, and can be frightened away by splashing'.
The advice of this 'Manual' 'are the dumbest that can be imagined', state the authors of an interesting book, 'Shadows in the sea'.
The sharks' bad reputation is as old as the first meeting of people with the sea. Yet many, including ichthyologists, until recently did not fully believe in the seriousness of danger that the sharks threaten people who penetrate ever deeper and further into the seas. They did not believe, because they did not know the sharks very well. Now we still cannot boast that we understand the sharks well. The sharks are still mysterious to us, as everyone, who has met them up close and personally believe. We still cannot be sure when, where and what shark will attack. Why sometimes children and scuba divers bathe and swim closely to sharks - and nothing bad happens? However, why the sharks sometimes attack bathers on crowded beaches, in the shallows, where water is waist deep and where nothing similar has happened before?
The shark is a mystery. That is correct. However, much in the vagueness that the shark represented has cleared-up in the recent years.
In 1958, scientists from 34 countries gathered at a conference in the University of New Orleans, USA. This was the beginning of CSS - the Commission of shark studies. It collects from around the world information about sharks, all the cases of their attacks on people. The circumstances of this aggression is indexed.
What are those circumstances, causes, making the sharks man-eaters?
The main are three, basically.
Fish, wounded or fluttering on a hook.
Clumsy swimming style of a swimmer and their fear before a shark.
Blood in the water causes the sharks to arrive from afar and attack. Even a simple scratch on a swimmer's skin provokes a shark attack.
In experiments, sharks shoved clearly 'gastronomical' intent when into their pools water from aquariums with frightened (intentionally!) fish was poured. Apparently, some substances that enter the water from wounded and panicked animals also attract sharks. Due to the lack of a better title, those substances can be called 'the smell of fear'. It was proven by experiments that some fish and amphibians have those substances. Probably the same goes for humans. In any case, out of several swimmers, the sharks chose the one who was 'uncontrollable, panicked movements'.
A shark pursues only the designated victim while the other people, even those rescuing the victim, remain untouched. However, this 'rule', has exceptions.
Sharks attack divers fairly rarely. Possibly they are frightened by the unusual appears of those recent arrivals in 'the silent world'. However, this also is not always the case. Especially if the 'human frog' holds the still twitching fish on their harpoon or on a rope at their belt. Therefore, it is recommended to attach fish to the longer ropes, about 5 m long. Thus a swimmer, distracting a hungry shark by a bunch of fish, avoids a direct attack.
The statistics have shown: in most cases shark attack swimming, walking in the water, standing there people, when their legs are in the water, and head and shoulders are above it. Therefore, for the scuba divers the most dangerous moment when meeting a shark is the exit from the water and surfacing.
If shipwrecks are excluded, then two thirds of all the registered attacks happen in the shallows, at depths no more than 1.5 m, at a 100 or around so m away from the shores, usually in the trop-ics and subtropics, where the temperature of water is no less than 18 degrees. However, here are also plenty of exceptions: there were cases of shark-caused deaths in quite cool water too, (12 degrees). In general, it is established: when water is colder than 15 degrees, the most dangerous sharks lose their appetite, are sluggish, and two-legged 'game', fortunately for it, does not attract them.
However, the seas for the last decades are growing warmer; the sharks widen their territories, swimming from the subtropics to shores of countries where they did not live before. People also widen their intrusion into the underwater world. Encounters of people and sharks grow by the year. Sharks began to more often attack people in boats, which was rare before. They break with their teeth and tails boats, rafts and surfboards, jump over the board, (even onto small ships!), or grab those people that sit there.
Various ways of protecting people from sharks were and are being invented. Still, some can be treated seriously only as means of suicide. Such, for example, are recommendations from the journals and books of fans of underwater hunting: 'You can swim up close to the shark and kick it and it won't harm you. Try to do it sometime'. Alternatively: 'If the shark approaches you, put the head under water and yell as loudly as you can: 'Go away'!'
From the more realistic methods of the defense, the most na§бve, and in the opinion of others - the most reliable, is the color of clothing. Some famous scuba divers recommend diving in dark suits or on the contrary in very bright, orange-yellow, (and scarily decorated: with toothy jaws at the back of pants to scare away those sharks that approach from behind).
Some shark specialists' state: white color clearly attracts the sharks, from two victims, dark and bright, it chooses the bright one. A tragic story of a white boat that pursued several days off the coast of Nova Scotia in 1953 by a shark (also a great white, i.e. one of the biggest and most dangerous) for several days is known. Boats colored different were ignored, and that one was drowned in the end.
Why then the Japanese 'ama', collectors of pearls on underwater mollusc farms, dive in white shirts and pants? In Japan, it is believed that white color frightens the sharks. Possibly, it is only a misinformed (and therefore dangerous!) debt to traditions. Still, the sharks only rarely attack the pearl collectors, despite their shining white clothing.
Chemists too participated in inventing shark repellents. One of such concoctions was prepared and tested during the last world war: cupric acetate, mixed with nigrosine, which colors the water into dark blue color, (supposedly for a greater intimidation of the sharks). Cupric acetate is the analogue of one of by-products of rotting shark meat. As it was suddenly discovered, it is most of all, among the other tested substances, unpleasant to the living sharks. This was proven in experiments and preliminary tests in the sea. However, later there were also misfires with this repel-lent, which during the war helped many sailors to get rid of 'shark fear' (as it is supposed, more psychologically than physically). Some sharks didn't flee from the chemical imitation of their 'ptomaines', but arrogantly devoured packets with the acetate of copper and other ingredients of the 'repellent'.
The pioneers of the 'Silent world' Cousteau and Dumas have tried the repellent in vain as well. Only the strike with the camera on the snout caused the attacking shark to retreat, (for several steps).
After the saving effect caused by the camera, Cousteau and Dumas, when entering the spaces of the 'Blue continent' began to arm themselves with sticks with nails, to politely shove away the shark, if the latter opted to meet them too closely without invitations.
Other scuba divers to protect themselves and hunt the sharks dive into the sea with more improved weapons. Some put onto the tip of the arrow of the harpoon gun an explosive or a needle filled with strychnine, which supposedly kills a shark in 30 seconds. Others have a 'warhead': a 2 m long steel pipe, which has a gun mechanism for a 12-caliber bullet, a corresponding load and a strike mechanism. Finally, the third protect the peace of their underwater excursions with 'electric fear'.
It was long known that fish and some other marine animals, entering an electric field, hurry to quickly leave from the sphere of influence of the electric current. Some time ago at the Durban shores (South Africa) put underwater an electric cable that generates an electric current and with such a barrier, they blocked the sharks from the beaches. Until then, from 1952, there underwater nets were used very effectively, blocking the sharks' entrances to the shorelines. It is supposed that an electric barrier is a more effective means. Then again, the nets also, if judged by Australia's example, are sufficiently reliable: from 1937 onwards, as they blocked Sydney's waters, 'not a single case of a shark attack was established'.
ALL LIFE IN MOVEMENT
The sharks are built thusly: when immobile, they choke even in clear water that holds enough oxygen. Pelagic sharks, aka those that live in the wide-open ocean, die in oceanariums too. Apparently, they cannot achieve there the right speed. Hence, they choke. Only at a fast movement does the water flow through a shark's gills in a sufficient quantity. A sluggish, dying shark, if it is not too big, the oceanarium's staff will put into a small pool with flowing water, and it happens that they save its' life, by 'flushing' its gills.
Sharks do not have a swim bladder; their average weight is greater than water. This is also why a shark must constantly live in movement, otherwise it will sink to the bottom as soon as it stops moving its' tail.
A shark swims by flexing its body in wave-like motions. The main movement impulse is provided to the shark by its' heterocircular tail, (almost all sharks have an upper tail fluke that is much longer than the lower one).
Another 'motor', this one quite modern, also belongs to the sharks - a rocket! Forcefully pushing water through their gill slits, they receive a reactive push forwards. Usually sleeping sharks utilize this mode of movement. Day and night, from birth to death, a shark is fated to move. However, it must sleep sometime! Nothing alive survives for long without sleeping and resting. Pelagic sharks, which live far from the shores and over great depths, sleep in fits and starts afloat, from time to time slowly twitching their tails and moving forwards with reactive jets, and therefore they don't sink.
Coastal species of shark, when sleeping, lay on the sea bottom. In the shallows, their immobile sleep does not threaten to sink them into the ocean depths.
Fish speeds are measured by a stopwatch, using for the guideline the speed of a ship that is coursing in a parallel direction, a camera, (counting via the shot shots, whose speed of movement is known). However, a car speedometer, attaching to a fishing line, gives the most precise data about the maximum speeds. A hooked fish, unwinding the line, usually leaves with all the speed that it is capable of. In addition, the line equally quickly updates the speedometer that is connected to line.
All of those methods give different speed data. The maximum among them are thus (in km/h): carp - 13 km; perch - 17 km; pike - 33 km; salmon, barracuda, Atlantic mackerel - 40; tarpon - 56; tuna - 70; swordfish, marlin, and sailfish - 100-130!
They are somewhere on the level of 'Atlantic mackerel - tarpon - tuna'. The maximum registered speed of a blue shark - 42.5 km/h, and of a mako - around 60. Undoubtedly, this is a good indicator: best steeds on the hippodromes race just as quickly.
A shark's strength is great. It happened that a single twitch of a big shark was enough to tear, like thin threads, ship cords 5 cm in thickness!
Steel hooks, caught in the jaw, straightened out. Chains that bound those hooks with fishing lines, endured loads of about a ton. However, the sharks tear them too! They break, squeezing their jaws, the hooks themselves, and they are 'half an inch of strong steel'.
A gutted, shot, pierced several times with harpoons, shark is still lively enough to bite off an arm, (this happened to one angler). Another shark, also gutted and thrown back into the sea, immediately was hooked again, swallowing its' own impaled guts.
Add to this incredible liveliness the knife-sharp teeth (in case of large sharks - up to 5 cm long), so sharp that you can literally shave with them. Those knife teeth can bite a human in two! In addition, the stretchable shark maw easily swallows crocodiles, sea lions, its 2-m-long relatives and even, supposedly, horses, (if the jaws are really large, as in the case of a great white shark). Do not forget about the sensitive sense of sharks' smell and the other organs that provide the precise data and orientation in the endless space of the seas, and you will behold a carnivorous monster unequal to anything in the world.
A drop of blood in an 'ocean' of water is smelled by a shark from a large distance, like the male silk and Saturn moths that can detect 1/100 000 of a mm of a smelly substance in the atmospheric 'lake': in a space that is hundreds of meters wide and 3-4 and more km long. The concertation of the 'smell' is impossibly small - a molecule in a cubic meter of air!
'We're working here with such a finely developed sense of smell that we cannot compete with it using the most sensitive and exact devices, which are used in our times to undertake a chemical analysis' (A. Hezler).
With the nostrils, that are below on its' snout, a shark does not breathe with, but only sniffs, so to say. It swims in the water, determining the exact location of the source of the smell. Which nostril is more intensively 'bombarded' by the smell's molecules, in that side the shark turns. If its' right nostril is clogged up, it will constantly turn against the clock hand's direction to the left, in the side of the functional nostril. Conversely - following the clock's hand when only the right nostril smells the smells.
Both nostrils were clogged - the shark swam past the smelling food. The shark's eyes were covered, freeing the nostrils from the clogs: 'stopped above the food'.
As it was recently discovered, the sharks' sight is also decent, the same for heating, but smell is its' main guide.
Smell and also the 'long distance touch', the seismosensory ability of the side line, which directs the fish in the right direction to the quivering prey, even if currents are taking the smells away from the shark and it cannot smell them.
The side line is a system of sensitive skin organs that go on each side of body from tail to head, (where that line branches). From the main elongated system, small channels (with nerves that penetrate them) separate perpendicular to the surface of the fish's body, and sometimes they open outside. This direct contact of sensory organs with the outside environment informs the fish about the smallest variations of the 'external' water. If the fish approaches some object or another fish, immediately the extra water presser on the side line's organs, created by this obstacle, allows to rather sense at a distance the surroundings.
Since water is a firmer element than air is, waves in it spread out more than four times as fast - with the speed of 1500 m per second. This means that the side line receives signals about the obstacles in the path and the other available to it information better than the ultrasound echolocation of bats does.
The sharks, which are excellently equipped with everything that is necessary for live and action at sea, have no doubts in choosing food. That eat everything that they bite into, even inedible and unappetising: crocodiles, sea snakes and turtles, penguins and other birds that live above the ocean, flying fish and bottom-dwelling fish (even stingrays that sting their foes with a venomous stiletto!), herring, cod, salmons - all vanish in the insatiable gut of the shark. Seals, dolphins, wounded whales, ship refuse, deer, horses, dogs, cats, chickens that somehow have ended up in the sea and plenty of other, even stranger things, are devoured and digested by sharks. Supposedly, even polish that is used to polish decks and metal objects. Horseshoes, swallowed with horse hooves are digested almost as quickly as bones and hooves. A shark's stomach juices have a great digestive power (on contact with skin they cause a severe burn).
Sharks and dolphins have hostile relationships. Many dolphins die in shark teeth. However, in the wild and in captivity it was often seen how dolphins, working as a pack, chased away and even killed quite large sharks. They batter the sharks with their snouts, striking their gill slits. Alternatively, pressing to the wall of the pool, (or throwing them out onto the surface), prevent the shark from breathing.
Sharks do not dare attack healthy whales. As a battering ram, a whale has much greater strength than a dolphin does. But they follow the whales at a respectful distance, as jackals do with lions, so that, at an appropriate moment, when a whale is wounded, to tear it apart, or to pick up scraps after the sperm whale.
Cainism is abominable, for the P.O.V. of human norms of morals: murder by the elder, stronger siblings of the younger - an often event in nature. Among spiders, cainism is commonplace. In birds of prey and owls, it occurs in lean years. In sharks, (it is terrible to think!), the not yet born offspring devour each other in mother's womb: in viviparous sharks ЁC for example, mackerel sharks, and sand tiger sharks - and, apparently, also in makos, which, true, are considered oviparous instead, but the devouring of eggs by embryos occurs in them too.
The pelagic sharks, inhabitants of open sea spaces, as a rule, are viviparous. The embryos develop in specially widened parts of ovipositors, reminiscent of the mammals' vagina. This shark ЎRvaginaЎЇ also forms in its walls a certain imitation of a 'nursery' or a placenta, through which the embryo also received nourishment.
Therefore, the embryos that were conceived earlier, grew up and are ready to abandon the maternal loins that have nourished them, in the last days before the start into the 'silent world' devour their underdeveloped siblings and still unfertilized egg. They rob before they are born! The shark pups by that time are quite prepared small carnivores, miniature copies of their terrible parents. And if it happens that a pregnant shark is killed, and its' belly is cut open ЁC the pups are swimming in the internal fluid well and dextrously enough. If they are released into the sea, they swim away, ready to devour everything that they can overpower, and it is hard to imagine that they did not always live there.
Viviparous sharks, due to the embryonal cainism, have only two pups per litter. This power couple eats everyone else before their birth!
The birth of the oviparous sharks is also unusual: they appear to be born twice. The first time is from an egg, laid, however, not on the bottom of the sea, (as in case off egg-laying sharks), but in the mother's womb, in the 'vagina'. There the pup feeds first on the egg's yolk. Then the yolk sac, with which the pup is connected via long thin tube, very similar to an umbilical cord, attaches to the wall of the 'vagina'. Through this sort of a 'life line' the blood of the mother shark provides the pup with everything it needs to grow and develop up to the 'second' birth, when after abandoning the 'vagina' this hungry, relentless creature, the last scion of ancient, but not aging, tribe, enters the external world.
Many of the sharks that live along the sea floor, lay eggs. Again they are not plain, not some helpless fish caviar. Their potential progeny is reliably packaged and protected from the foes. Eggs that are fertilized in a shark pass in the ovaries past a special gland that gives each of them a protective capsule: oval, four-cornered, pear-like, spiralling. They have different configurations and also colors: crème, yellow, black, brown. However, they are all made from a substance that is similar to keratin that gives strength to pincers, hooves and horns.
Therefore, the egg's capsule is strong, when it hardens, and it is big: in case of a whale shark - 63 cm by 40. Its' ends and corners got tendrils. Soft at first, they easily encircle underwater plants, corals and stone crevices, and when they stiffen, they hold fast.
THE MARCH-STRIKE OF THE 'RED' FISH
There are times in a fish's life when it, to say it gently, loses its proverbial cool-bloodedness. And also its' appetite, caution, and, as people say it, common sense. Cautious pikes hang in the shallows, at the very edge of the coastal clutter. And there it is easy to stun them with a stick. The common bleaks can be caught by hand. Even the tiny paradise fish, ambassises, and other prisoners of the aquariums aggressively and bravely rebel against any intrusion into the 'territorial waters' that they consider to be theirs. Angrily they charge even at the kindly hands of their owner from which they usually got food. In desperate leaps from the water, they attack even the owner's face.
Can you guess when this happens?
When nature calls them out to reproduce. When, forgetting about everything, some fish seek, find and bravely defend a bunch of seaweed, a small space on the bottom or at the surface of the water - to each his own. It is an individual's territory. From here on it will be a protected place, guarded for the next generation and the piscine family, (for some fish species it is so).
Others, gathering into grandiose swarms, swim far from their home waters. (The time has come for the spawning migrations). The leave from the seas into the rivers. From rivers into the seas. The salmon demonstrate the first example. The second - by the river eels.
The North Atlantic salmon, the brown trout and their Pacific kin: the Coho salmon, the Chum salmon, the pink salmon, the sockeye salmon, the Chinook salmon and the masu salmon, annually, and - every species in its time - go from the seas of the Northern hemisphere into the rivers to lay their eggs at the source.
When a mighty instinct gathers all of the fish who need to breed to the mouths of the rivers, they swim there immediately. For some time the salmon swim here and there at the edge of fresh waters. Then, suddenly, all at once and in such 'great numbers' they go up the river that they literally fill it up. The water is swarming with fish. Some have the dorsal fins and the backs protruding above the water: the other salmon press them from below. And in places, where a shallow river narrows, the fish at the margins are pushed even to the shores by the pushing fish swarms in the center.
When the pink salmon swims up the rivers, it is the time of a great feast for foxes, bears, crows, lynxes and other beasts and birds that charge at the salmon and acquire them each in their own manner.
And the salmon hurry further and further upriver. Teams split from the main army and go into the side channels, they swim up the streams that are connected to the river, and they reach the very river sources. The fish via acrobatic jumps bypass waterfalls and rapids that now are met at every step. They often jump three m upwards and five forwards. Some fail: they fall after the desperate jumps not into the water behind the waterfall, but onto dry cliffs and rocks. Many die, but many safely 'land' and continue their journey.
In some Alaskan rivers, the Yukon, for example, the Chinook salmon go for 4000 km from the river mouths!
The Pacific species of salmon enter the flowing waters of the continents in summer, and every species - at its own time: the earliest of them all, in May, the Chinook salmon storms the rivers, the tastiest of them all. The Americans call it the royal salmon, and the Japanese - the prince of salmon. Then go the sockeye, the muso, the pink, the Chum, and only at the end of August-September - the Coho. As soon as they arrive at the spawning grounds, the fish spawn.
The Atlantic salmon spawns in autumn and winter, and not immediately after it enters the fresh water.
'In general the salmon biology is incredibly complex: in each river its' life is unique' (the aca-demian L. S. Berg).
The Atlantic salmon, just like the wheat, has two forms, the summer and the winter. And the similarity is not just in the names. The winter sorts of wheat, to continue growing, must winter be-neath the snow. Only after the cold 'treats' their cells in mysterious ways, they begin to fruit in the next summer. Ditto the salmon: the winter sorts must, to ripen its eggs and sperm, to winter under the ice in cold river water. The summer sorts do not need that.
The Atlantic salmon enter the rivers several times a year. In spring, as soon the rivers are free of ice, the 'ice salmon' appear. These are large females with underdeveloped eggs. Probably they have gathered since the last autumn in the mouths of rivers and wintered there.
In July, the rivers are besieges from small, about one-two kg in weight, salmon that are mostly males. These are young fish that hurry to bring their offspring into the world. They just spent one year in the sea, as soon as they reached one year in age - and they are already back in the rivers to reproduce. Other salmon live longer in the sea, for two-three years, without spawning.
Finally, from the end of August and until the frosts, arrive the 'autumn' salmon - almost all of them are large females without mature eggs.
Now, the salmon that left the seas in summer spawn in that same year, in winter. And the 'autumn' is the winter breed: only after a year, in the next autumn and winter, will it spawn.
As soon as the salmon enter the rivers, from the gluttonous carnivores they became the fasting yogi. While they live in rivers, they eat nothing. Stores of fat accumulated back in the sea support their strength. They do not have time to eat and they have nowhere to 'store' the food: the sexual organs of the fish grew so much that they push out the sides and squeeze shut the intestines. The coloring changed: it is not silvery as it was in the sea, but dark. In case of the Atlantic salmon - with red spots on the sides. And there grew a hump on the back, it is especially tall in the male pink salmon. Plus, the males' jaws distorted like pincers, as the crossbills' bills.
The salmon spawn in quick-flowing streams with transparent water and rocky bottoms. To reach them they often go to the very sources. They spawn in such shallows that the fish have to lie on their side - only then does the water cover them completely. Each fish goes only where, in that same river and even that same stream, where it itself was born several years ago.
The males jealously guard their females, chase away the other males. Before laying its' eggs, a female clears the designated spot from garbage, silt, and waterweeds. It lies on the side and slams the tail: silt goes upwards, revealing sand beneath it. Then the female digs a pretty deep pit in the sand - 2-3 m long. There it lays several thousand eggs. With tail strikes, it covers the pit with sand and pebbles. It makes several such nests. The work takes two or three days, sometimes a week.
Then the female salmon guards the next. It stays, awaiting death, at the cradle of the new life. May female salmon perish at the nests from exhaustion. Many males also die in that same river. Exhausted, mauled, sick, they feebly swim down the current; the waters carry some quickly, backwards and upside down.
'Many tribes of the Pacific salmon are worth noting that they are born and die rivers, but mature in seas and only once in their lives they spawn and mate' (S. P. Krasheninnikov).
That is so with the Pacific salmon. But some European specimens of the Atlantic salmon return to the sea alive and well from their hard trips to 'the promised waters'. In sea they recover, greedily devouring herring and lesser sand eels, recover, fatten, and by the next year they are ready to travel again.
No more than one quarter of all European salmon, and sometimes only 2-4 percent return to spawn a second time. Very few return to the rivers thrice. And in Scotland, an old female was caught. Thirteen annual rings were counted in its scales: ergo, the fish is 13 years old. No salmon older than her was caught. They continued to investigate further and discovered that the venerable salmon has visited Scotland four times already and came to spawn a fifth time. It is a record.
In spring, the young Pacific salmon usually go into the sea (only the young sockeye live in rivers for 1 to 3 years). But the young Atlantic salmon do not hurry to visit Neptune. One, three, five years they grow in rivers and then all at once, in masse, abandon them. And it happens that in places where only yesterday from any rock, you could see their happy swarms, today you will not meet a single young salmon.
But not all of them leave: some males remain in rivers. Why? This exception from the rules have a big biological meaning. The thing is that the male Atlantic salmon die quicker than the females do. They almost never return to the rivers a second time, thus sometimes there are not enough males on the spawning grounds. To compensate this loss, some young male salmon remain in the rivers. In fresh water, they grow poorly, but sexually mature quickly and are always ready, if the big males are not around, to fertilize the eggs of a female that returned from the sea. These dwarf homebody males develop from the same eggs as the other salmon do.
The Ladoga and Onega lakes have salmon (female and male) that also do not leave for the sea. Big lakes replaced the sea for them: annually, at the appropriate time, they go to spawn into the nearby rivers and then return to the lakes anew, thus reproducing the entire migratory cycle of their species in miniature.
The brown trout too stays permanently in some montane rivers and lakes. Thus, the famous trout is a special breed of the brown trout. The brown trout is a salmon, closely related to the Atlantic salmon and spawning in the same rivers that the European specimens of the Atlantic salmon do. Also, the brown trout lives in the Black, the Azov, the Caspian and the Aral seas.
The Wyg River empties into the White Sea. Once, in this river, an Atlantic salmon was caught with a Norwegian mark 'June 10, 1935'. The soviet anglers caught it two months later! The Atlantic salmon in question was a female and hurried to spawn up the Wyg, where it was born six years ago. Who could imagine that the Atlantic salmon leaves the mouths of its native rivers so far behind! For from the western coast of Norway, where it was caught for the first time, it had swam two and a half thousand km. It covered the same distance on the way back, but now it was in a great hurry: for the Norwegians had delayed it with their marking procedure. Daily the fish had swam on the average around 50 km!
In its journey, the salmon saw hundreds of rivers quite suitable for spawning, but the fish sought out the one where it was born a fry. It swam continuously in a straight line, in a well-known route - otherwise, if it knew the route poorly, it would have wasted much more time for its' heroic raid. For 50 km daily is a great speed for the salmon. (The record is 100 km daily).
On Kamchatka, when salted fish was loaded, a marked Chum salmon was found. It was marked on the Unga Island, near Alaska, and it was caught on the other side of the ocean in about a month. A pink salmon, marked in Korea, swam more than 1600 km in 2 months and was caught by people once more in the Amur bay.
An insatiable appetite sends the salmon from one end of the sea to the other. Chasing swarms of herring, they do not refuse the other fish that they can swallow. In the sea, the salmon grow six times faster than they do in the river.
At the end of a second year living in the sea an Atlantic salmon weighs already around 5, and by the end of a third - more than 8 kg.
Only a few Atlantic salmon feed for 4 years in the sea. Usually, not spending even half of that time, they return into rivers for their first spawning. And as we already know, some spend in the sea even half of that time. Ditto for the pink salmon: it is a fast-growing member of all the salmon species.
An Atlantic salmon that is especially lucky in life grows up to 1.5 m in length and weighs 40 kg.
It was decided to check: the salmon are born with the knowledge of their native shores or the fish acquire it after they hatch and live in a river for some time?
People transported the salmon eggs from the streams, where they were laid, into other rivers. When the fry hatched, they were for some time fed in special nurseries. Then the young salmon were marked and released into rivers alien for them.
And what happened? After several years having swam in the sea, the salmon returned to the rivers where they had lived as youngsters, and not where their parents laid them. Thus, the knowledge of the spawning grounds is not an inborn one. It acquires during the first years of life and retains in memory for at least 2 to 4 years while a salmon lives in a sea.
What marks does the fish remember? Chemical ones, apparently: it remembers the smell of home, the taste of the river water where it lived its' youth.
Experiments shown that many fish have simply a phenomenal memory when it comes to smells! And a very fine sense of smell too. A gudgeon, for example, is 250 times more sensitive to the smell of rose oil and 512 times to the sugar dissolved in water than a human is. It also distinguishes the water of one river from another.
When salmon had their nostrils clogged and released into the sea, they could not as precisely as before remember their native rivers. They swam mainly by guessing. Thus, the sense of smell, when it comes to searching for the path, play a very important role, but not a unique one, since it doesn't solve the entire problem. For, when going into the sea, the salmon swim truly far away from the river mouths to which they return afterwards. So far that no smell of home can help when they begin to go back.
What helps them then? Nobody knows. Maybe the sun and the stars serve as guides...
LIGHT AND VISION
Not everyone clearly visualizes a sloth, or, say, an orangutan, even though we share an element with them, but it is hard to find anyone who had not seen a fish. For it is easy to see them - just enter a... food store. Fish - are our food and this role of theirs, according to oracles, will increasingly grow in the future.
What variety of forms! Prototypes of torpedoes, missiles, arrows, cannonballs and throwing discuses supremely easily pierce the watery depths, making unimaginable trajectories in them. More-over, this does not even look like a fish: a snake! Yes, it is an eel. In addition, this monster, luxuriating in the soft silt, impressively forewarns various sluggards: it lay for so long that it became completely flat. Even its eyes have moved completely onto one side! Animated figurines of knights from the chessboard of Neptune himself... Fish that can be much more easily be taken for knots of barbed wired... Fish, armed with surgical instruments, swords, or just idyllic fishing rods; fish that are almost truly winged... In short, the variety seems endless!
Moreover, all of them glow and shimmer with such a multitude of color that one begins to think biologically blasphemous thoughts: all of this great coloration is not for disguise and not for intimidation - but for beauty!
Fish great and small... The legends speak: the curious Alexander of Macedon descended to the bottom of the sea in a glass vessel and saw on the seafloor such an immense fish that it took three days to swim by. William Bib, and after him - many more Russian and foreign explorers of the depths, did not discover such a fish. However, there are fish seven meters long.
In addition, the smallest fish, according to the scientists, is the pandaka of the Philippines. It is literally a fish big enough for a single tooth: seven mm long. For a while, fashionistas carried these fish in... their years. In crystal aquariums of earrings!
Simple or fancy, sweet or scary, big or small - all of them are pretenders to the roles of our ancestors, and it is hard for us to refute this relationship: when we are embryos, we too have gill slits...
Just as we do, the fish see, hear, smell, although it must be pointed out that some of the fish are eyeless or hard of hearing.
However, the life of a suppressing majority is equipped with a color vision. If among the mammals only a few possess color vision, then among the fish it is common.
In the past, to catch sardines, an Italian angler would store... logs. At night the barge, setting a huge fire at its back, the light of which would pierce the water for thirty meters in diameter, would go out to see.
It was a majestic sight, and the fish would appreciate it first: soon a swarm of sardines would begin to gather, pushing closer to the light. Then the barge would take the course back home and the fish, mesmerized by the sight of flame, would go with it. Having reached the coastal shallows, the original fire would be put out, and in its place, another fire would be lit on shore that was just as bright. The confused fish would swim to it, and the normally cautious sardines would not sense how a net surrounded them...
Once, on the shore of the Drevyato lake, (located in the former Kovenskaya district), appeared a red-sided traction engine with a dynamo-machine and a big electric lamp that was designed to be lowered into the water. 'It won't work', -- said the skeptics from the nearby villages and were proven right. Just not fully. When, having chosen a darker night, the unusual anglers did a first cast of the glowing fishing rod; a cloud of fish filled the glowing space. Sadly, the fish there were not to the commercial standards: much too small. 'But where are the zanders?' - the inventors wondered.
However, the zanders did not appear, no matter how deep the equipment was lowered...
They could not appear. The reticulum of a zander is shining, rich in guanine - a substance that while reflecting even the weakest light, makes the eyes of this fish into the most sensitive equipment. The distant light of the stars is enough for this predator to see excellently in the dark; a strong light simply scares the zander, and naturally, this fish hurries to leave such an unpleasant place.
As for the small fish that swam to the light of the Drevyato's experimentators, they, just as sardines, and the multitudes of other so-called daytime fishes, have differently designed eyes: their reticulum is strongly pigmented with melanin - a substance that consumes light.
The light of a false dawn gathers these fish, calls them to an active lifestyle, they swim to it, and end up, de-facto, in a tight sack.
Light attracts sprats, trachurus, European anchovies, Atlantic mackerels, salmons... The European anchovies, gathered in the light pillar of a projector, are sucked in via a specially designed fish pump.
The Pacific saury is caught with somewhat greater difficulty. At first, the ship sails at night, seeking this fish, scanning the sea with a projector. If they find this fish, it is seen immediately: this species, crazed by the sudden light, jumps out of the water.
Here, the captain of the fishing boat gives the order 'stop!', and the crazed fish is pacified with a blue light. Having pacified the Pacific saury in such a manner, that it is too early to grow active, the morning has only broken, this fish, collected into a compact swarm near the vessel, compact even more, lighting-up the red projector. Then it is enveloped in a net from below and pulled out of the water.
Even simpler is the method to catch salmon, invented by the Norwegians. They paint coastal cliffs white, and put the net between them and the water. Confused, the fish in question swim to the lighter colors and are entrapped and caught.
Sadly, to catch fish that fear the light (lamprey, tuna, Atlantic bonito, eel - and there are much more species), the electricity had not brought an equally significant breakthrough.
Although, when it comes to eels, back in 1905 a certain Petersen from Norway offered a very witty electricity-based means to catch these fish: in the shallows, where it is easy to catch fish - fish traps, and around, on a wide area - hundreds, maybe even thousands, of lamps. The eels that would hide there would not endure the light pressure; they would swim into the darkness and be caught in traps. Sadly, it is unknown if this method was tested. In any case, the eel remains one of the hardest to catch fish.
Before the revolution, a way to catch lamprey on Volga in winter 'via the lamp' was known. Where the current was fast, a hole was cut in ice; next to it, a light source was put. Lower down-stream more holes and around them were people, armed with nets. The lampreys, swimming past the illuminated spot would be scared, and carried by the current, ended in nets.
As a rule, fish fry hurries to light. That is understandable. They feed on plankton, and plankton is where the light is! As they grow, some of them change habits.
The global ocean devours light with a crazy appetite. It has been calculated: if the sun is in the zenith, and the sea is smooth, 98% of energy of the direct sunrays that touch the surface will be consumed by water. This quantity, of course, diminishes as the sun goes down, but the sky with a mass of scattered light remains above the sea. That light gets consumed as well.
Three quarters of our planet is taken by the global ocean. This giant consumes so much light that so far no computer can express it in numerical digits. A big part of the rays' energy goes to heat the water. The rest tries to brighten the gloomy kingdom of Neptune.
Sadko, a rich guest, apparently stayed in the shallows, (no more than five meters deep); other-wise, he would not have seen many colors. After the indicated mark, green and blue ones replace the whitish-yellow tones, common to our vision... It grows ever darker...
Even somewhere with virginally clear water of the ocean, the brightness of light during diving diminishes ten times at every fifty meters. In about four hundred meters away from the surface, the sun is powerless...
However, the depths glimmer with ghostly lights. Here, the animate, (and there are info, that the inanimate as well), themselves provide the illumination. Various small critters shine as bright dots. Here even the squid, showing the well-known trick with its double, casts from its' siphon not an ink clone, but a bright, colorful one.
Moreover, here the fish too glow in the dark. Some have basic lamps, built-in for convenience into one or another body part. The others shine as if they are encrusted with gems. There are even such that glow completely, resembling the negative images on a black-and-white photo film.
Falling into the water, the ordinary sunlight immediately, if one can put it so, stops being itself. Water is a giant light filter, or, more correctly, a most complex combination of filters that break-up the light in the most confusing, and on occasion in the most bizarre manner.
A person, who descended for the first time onto the depth of fifty meters and wounded a finger there, will see something green leaking from him. This is how blood looks in the water.
A gloomy kingdom. Dim shades or darkness. Nothing rejoices the eye. And only if into that world, where its' inhabitants move like ghosts, the strong light of a projector will cut in, then everything will play with bright colours - a palate of an artist who loves the local colors!
You will involuntarily think: what beauty is wasted! In addition, what for it is for the inhabitants of the gloomy world, if it is not seen?
However, who knows, maybe they see more than we suppose...
Experiments have permitted to establish: an ordinary small Crucian carp that lives in a peat mine in Shatura can see a mosquito larva with one in twenty-milliard share of daylight. We, in the same circumstances, will not see an elephant.
Various waters, various depths, very varying eyes...
Nice nearsighted eyes, opened wide as if in surprise. An angler on the tall shore of the Oka River can be calm: the large zanders, pikes and burbots that swim in fore waters almost cannot see him - for them everything is murky in the direction of land. A pike, for example, is famous for its sharp eyes, and it sees its' prey only from two - two and a half meters.
The fish eyes are not above various optical enhancements. In the fresh waters of Central and northern South America swims an amusing four-eyed fish. It remains in the water, as it is supposed to, but the eyes are half above the surface. They are divided into two cameras: the top ones, (with a flatter eyeball) watch in the air, the bottom ones look into the water.
The eyes of the deep-water kin of our ordinary salmon are just as good (the barreleye family, order Argentiniformes). The Bathylychnops, the biggest (up to 50 cm) of them all, has two eyeballs in each eye. One of them, which is bigger, sees what is above, and the second one looks below and to the side. Now there is a fish that if it gets curious, does not need to whirl its head around: it is already provided with an all-around vision. Other barreleyes have telescopic eyes. They are elongated upwards in cylindrical shapes, their field of view is narrow and therefore - binocular.
The Scopelarchidae fish (deep-water fish from the same order) overpower the surrounding dark-ness in a genius way. Spots of pearl color glow at the bases of their telescopic eyes. They light their path with literally shining eyes.
Yet it must be admitted that such wonderfully original fish are not that numerous in the underwater world. An overwhelming majority must use eyes of ordinary shape, albeit equipped with internal mechanisms of surprisingly fast and accurate pinpointing the prey. Something just has to flash by - and the fish immediately grabs it. The moving muscles of its body execute without mistakes the leading orders of the eyes (currently, physiologists are successfully studying these excellent abilities of them).
'The most surprising is that this inborn reaction, known under the name of the 'aiming reflex' is observed in the majority of fish as soon as they hatch from their eggs. Apparently, its' mechanism is encoded in the genes and is in the brain of newly born fry practically 'ready'.' (B.V. Loginov, A.I. Gabov).
It is necessary to distinguish the form in details - whether it is a predator or prey. The fish do so. The pike and perch, charging at a fishing lure that the angler has chosen to be the one from a magnificent set - is this not the proof! Moreover, this truth became persuasive after lab studies. It was proven that fish learn and remember various geometric figures and it is not easy to trick them in this field. For example, the aquarium goldfish can distinguish between the two circles who differ in diameters by only three mm. In addition, the famous sticklebacks recognize a familiar object even if an unfamiliar side is turned towards them.
The thymallus, an eager hunter of fast-flowing rivers, if you get the chance to watch it for a long-er period of time, will surprise you at first by precise strikes after various prey items located on the surface of water, and then, if it will start to drizzle, it will disappoint you with shameful misses. The rain ruined the perspective, hence the cause of misfires.
However, the rains have went for a week... Knowing, that now it is in vain to catch via lure (a fake bait swimming in the water with a hook inside), the thymallus will hopelessly miss, anglers stay at home. On the seventh day of rain some arrival, dismissing everything, puts on a raincoat and, followed by mockeries, goes to fish. However, the jokers are wrong! In the evening, the angler returns with a rich catch. It seems that the thymallus is caught just fine! Now, of course, everyone decide to go fishing tomorrow, regardless of rain, plus by the next morning the rain is over too, and the sun is shining. Everybody casts his or her fishing rods, but... the thymallus misses!
In addition, it is understandable. Having grown hungry in the bad weather, the thymallus learned to adjust to the rain in their strikes, and when the bad weather ended, they could not immediately readjust.
Can you imagine, they too have optical illusions...
ARCHERS AND SPEARMEN
The archerfish were kept in aquariums for a long time, but not everything is still clear in their biology and even the 'technique' of archery.
How they are shooting was seen by many, but the composition of their 'cannon' was described only in 1926. However, until recently, all sorts of tales regarding the behavior of the fish before the shooting were found in literature.
The ichthyologist K. Lulling from Western Germany, in his monograph 'Archerfish', written in 1955, described in details the conditions, necessary to keep them in the aquarium, their diseases and their treatment, the histological anatomy of the eye and the behavior of the fish during the shoot. In general, from his work and from the works of others, the following was established.
The elongated indent on the roof of the archerfish's mouth, when the fish presses its meaty tongue onto it, turns into a sort of small-caliber rifle barrel. Before the shot, the archerfish fills its mouth with water. Then squeezing hard its gill-lids, the fish pushes the water out of its rifle-mouth. The dexterous tip of the tongue, rising and falling acts as a valve, and depending on its position the archerfish fires a thin stream of water or a series of droplets. At the same time, it keeps the tip of its muzzle underwater.
After selecting its target, the archerfish carefully stalks it, trying to be as close to its goal as possible, and trying to come upon the 'firing position' directly beneath the target. The last is understandable: the rays of light, falling vertically, are less distorted in the water, and the sniper fish has an easier time to correct the refractionary distortions.
Sometimes, while aiming, it moves slightly forwards or backwards. Then, after turning to a certain angle to the vertical line, the fish tries to position the goal to a similar direction away from both eyes in conjunction with the trajectory of flight of the water 'bullets'. If there is a miss, which happens rarely, then the second shot is more correct: the archerfish, so to say, figured the problem out!
After several shooting exercises the archerfish loses interest in that affair. Food, gained with the 'archery' is not the most important part in its menu; it is often sated by what it finds on the surface of the water, on its bottom, among the aquatic plants. But if it is hungry, then it 'shoots' at everything that however slightly reminds the fish of a desirable prey - an eye of a human which close to the water's surface, a lit cigarette. The Malayans are using the shooting enthusiasm of the hungry archerfish for a long time now.
In Indonesia, the archerfish are taught various tricks, and then competitions are held. The trained archerfish show-off their art during those times. For example, they extinguish lit matches and candles with successful hits. Not only the accuracy, but also the distance of the shot is taken into account. The most 'long-reaching' fish supposedly shoot up to 4-5 m. The most accurate distance is 1-2 m.
The 4-6 species of the archerfish family (the Perciform order) dwell in brackish and marine waters of the mangrove copses and river deltas, as well as in the rivers proper on the shores of the Indian Ocean from the Red sea to India, Malaya, the Philippines, Indonesia, and Northern Australia. The biggest archerfish reach 20-25 cm. The fry of these fish glow, but it is not real bio-luminescence, but a reflected green light, which, supposedly, helps these fishes, social as fry, to find each other.
The spearman is the swordfish. It was excellently described by Ernest Hemingway, who knew both the habits and the active, courageous attitude of the astonishing fish. It charges through the sea with the speed of a hurricane - 100-130 km/h. That is in the water, where the resistance is far greater than in the air. And how many birds can fly with such a speed?
Its' stylish 4-5-meter-long body (if the swordfish is really big) is pushed forwards by a half ton spring of muscle. The meter-long sword on the nose (the upper jaw is stretched forwards like a spear) cleaves the waves. This is both a hydrodynamic adaptation that lowers the frontal resistance of the water in the fish's way, and a dangerous weapon. Crashing into boats at a high speed the swordfish often pierced them. One of the boats was literally pierced through both sides! There's an excellent photograph - the witness of this incredible, supposedly, piercing power: the swordfish, stuck across the boat - the spear-like snout in one side, the tail's in the other. The anglers survived only because on sat on the prow, the second in the nose, and both fell into the sea from the blow.
The British museum keeps a piece of oaken board, covered in the front with copper, which was pierced clean through by a broken-off spear of the swordfish. The broken-off shards of the bone swords were found in the bottoms of the ships. Also in whales and sharks.
It is unknown, however, why the swordfish needs such pointless attacks? Are those accidental collisions, the result of unbridled fury, insanity for some reason...?
In any case, the composition of the head bones, especially at the base of the sword, is such in this fish, that the counterforce is experienced by it without any fatal after-effects in regards to itself. The empty spaces, filled with fat, the natural hydraulic amortisator, soften the counterblow.
These fish are not social, but around the swarms of mackerel or herring they gather in great numbers: each one came after its share of prey and keeps at a proper distance from the others. Like a hurricane they burst on the swarm, stun with the power of their strikes, slash and stab with their swords both squid and tuna, even the sharks (those that are not too big, of course).
The spawning of the swordfish is in the tropical waters of the oceans. To the south of the Sargasso Sea, for example, lies one of their biggest spawning grounds. Some breed in the Mediterranean Sea. Each female spawns many millions of eggs. The caviar floats in the water. The fry that hatch from them are unarmed with swords. But they grow up to 8 mm in length - and their noses stretch.
Meanwhile, the parents, after laying the eggs, scatter through the seas. Various sea fish goes to feed in the waters of the temperate latitudes, where's more food and the swordfishes follow them. Then they swim in our Black and Azov seas, sometimes into the Baltic. And in the north of the Atlantic ocean - to Iceland and Norway. Usually the swordfish hunt close to the surface, but they can submerge to the depths of 800 m.
The marlin, a close relative of the swordfish, is very similar to it: by the crazy attitude, by the magnificent jumps over the sea, and by the speed, which perhaps is even greater. In size some species of the marlin, perhaps, surpass the swordfish (length up to 5 m, weight 700, and perhaps even more, kg). Their upper jaws are also stretched, though far shorter than those of the swordfish are. This weapon is rather a rapier: round in the cross-section. The swordfish's is sharp at the both edges, flat as a sword.
Some species of marlins live in the open spaces of the tropical ocean zone. The sailfish and the spearfish - also belong to the Istiophorid family, just as the marlins are. And the swordfish are the only species of the Xiphiid family. Both of these families are joined into a special suborder of the Perciform order.
The sailfish have a very big (two-three times bigger than the actual body) and almost as long as the fish itself, dorsal fin. Moving quickly (up to 130 km/h!) its sail is folded as a fan into a special indentation on the back. At sharp turns, it seemingly grows from the back, working as a break and a stabilizer. The spearfish are similar to the sailfish, but their dorsal fins are much lower, and the tallest rays there are front ones, not the ones in the middle.
'On quiet days the sailfish may sometimes be observed at the very surface of the water, when they quietly drift with fully stretched and jutting through the water surface dorsal fins, possibly using wind power to move themselves. The biggest sailfish reach 3.3 m in length and weigh around 100 kg' (professor N.V. Parin).
In South America, in Guyana, Amazonia, the new arrival often hears such stories, for example:
'This happened on Rio Negro. (Or Rio San Francisco, Shingro, Aragua...) My father was yet a boy. They swam with grandfather to an island for the terrapins. And when the boat ran onto a sandbank - father fell into the water. (Possible versions: went to take a bath, to pull out a dead caiman, dropped by mother - it happens! In short, one way or another, he ended up in the river.)
Soon he safely got ashore. He walks and he senses - something's wrong... He hears: everything is loose and clanking within him. He looked at him... Great God! There was only the skeleton left...'
The understanding smiles of the interlocutors wordlessly explain the meaning of the joke, in which, as it often happens, there is a well-known portion of truth. Something similar does indeed happen in this country...
...The Native Americans of several local tribes, living at the edges of the swamps, where during the floods of the great rivers the entire neighborhood gets flooded, do not bury their deceased as usually, but first submerge them into the river water. After several hours they raise the bones from the water, and coloring them in traditional colors, they bury them when the floodwaters submerge, and green hills emerge in some places.
...This also happens: the wild peccary, fleeing from the jaguar, jumps into a river. It swims for several meters, and then the current bears its bloody body, and soon only the lifeless skeleton of a previously powerful beast dances the terrible dance of death in the water. Blunt-faced carnivorous fish, swimming in a large, dense pack, crowding each other, push and shove the skeleton, ripping away the remnants of meat from the body.
The piranha means 'slut' in Portuguese. Meanwhile, in zoology, it is the name of 12-16 species of fish of a specific family of the Characid fishes (order Cypriniformes). They are small fish: the biggest of them are 30-55 cm. But their bulldog jaws (the lower jaw protrudes forwards) - like the barbed maw of a trap! - are full of strong, deep-rooted and such sharp teeth, that a piranha can instantly bite in two a finger-thick stick. It will bite off a finger, too. The piranhas are a true nightmare. Wherever they are numerous, a rare person, even in the greatest heat, will risk going into water even to their knees. Never mind actual swimming, of course: they will quickly prepare him to the well-known anatomical 'specimen'.
The first conquistadors, who arrived with Orellian up the Amazon, already encountered the piranhas. Later on, few descriptions of these places and fewer films about the Amazon events do not talk about these fish. However, in our times, the doubts emerged: are really the piranhas so terrible? It was discovered that the natives are not so scared of them. They bathe and catch fish were the piranhas are plentiful. Wounds occur, but rarely. Few people are killed.
Only four are dangerous out of twelve or more species. The most terrible are the common, or the red-bellied, piranha - 'saikanga' in the native tongue - and black piranha, common in the watershed of the San Francisco River (one must added that it flows through the quite inhabited areas of Brazil). But even those do not always threaten people with an immediate and terrible death. The carnivorous attitude is usually demonstrated by the piranhas only when they are hungry or where the waste from slaughterhouses is dumped into the river. Up and away from such a place, though, they are no longer so dangerous. The stage of their aggressiveness depends from many, still unclear, reasons: how many of these fishes are in a certain areas (the 'group effect' with a critical number of approximately nine fish), of some, apparently, substances - the pheromones, excreted by the piranhas (if the water in the aquarium, for example, wasn't changed for a long time, the piranhas grow angry and attack each other).
In some rivers of Brazil the piranhas were tried to be killed off by various poisons. The effect for the objects of the destruction was insignificant, for the other inhabitants of water - quite noticeable. This should not be done, according to some specialists, because the role of these fishes, just as all other carnivores in nature, is sanitary and eliminating: they destroy most the sick, the weak, the degenerate animals, thus rejuvenating and perfecting the populations of their victims. In addition, these fishes are quite edible; they are often hunted, especially by the natives. The 'iron' jaws of the piranhas successfully replace scissors, and their teeth - knives, in the natives' households. The natives, armed with the blowpipes, according to Dr. Jacques Sheri, carry the teeth of the 'man-eating fishes' on their belts. Before firing the blowpipe, the poisoned dart is incised not far from the tip. The tip breaks-off in the wound and the poison acts quicker.
The relatives of the piranhas, which have settled across the ocean, in the rivers of Africa - the tigerfish - also occasionally attack swimming or bathing people. Their teeth are sharp as the stilettos. The goliath tiger fish is especially dangerous. It is thrice as big as the biggest piranha - up to 1.5 m - and weighs up to three stones! The tigerfish live and hunt in swarms, as the piranhas and the barracudas do.
'The barracuda too is quite safe for the underwater swimmers. If one discounts the long tales about the underwater world, I never read that a barracuda would attack a person. We often encountered barracudas in the Red sea, the Mediterranean sea, and in the tropical parts of the Atlantic, and none of them even showed an aggressive intent' (J-Y Cousteau, F. Dumas).
This statement of the famous experts of the 'silent world' sounds strange at the very least, few, apparently, would agree with it. (Including Hans Haas, a no less experienced diver than they are.) The reputation of the barracudas is very poor, the divers, especially the professionals, fear them in some places more than the sharks. Undoubtedly, the barracudas attack people. This is even done by the relatively small (1 m long) Mediterranean barracuda, which sometimes appears among us, in the Black sea. The bigger, two-three meters long barracudas attack without fear, as quick as lightning, and immediately depart after the first strike, do not repeat their attacks repeatedly, as the sharks do. But even from a single strike a big barracuda inflicts terrible wounds: the shock from the pain and the blood loss can lead to fatal results.
The barracudas resemble the pikes. They dwell near the coasts in the tropical and subtropical waters of all the oceans, in summer they visit the temperate waters too. The barracuda family (the Mugilid order) consists of 18 species. The smallest reach 30-50 cm. The biggest are up to 3 m and possibly more in length.
...Once, William Forster decided to take a walk in the town. He was a squatter, bred sheep, and lived on a farm in Queensland. Then he grew tired of it and he moved to Sidney. One day in 1869, Forster decided to look around the city.
He went to the museum. There he met Gerard Craft, the curator of the museum, and they talked. Forster asked among other things:
'Sir, why your museum has none of the big fish that live at our place in Burnette-River?'
'Big fish? What big fish?'
'The barramundi. We also call them the Burnette salmon. There are many such fish in Queens-land. They look like fat eels, five feet long. Their scales are thick and large. And can you imagine, only four fins. All are on their bellies.'
'You know, Forster, I've no idea of what fish you're talking about. It would be good for the museum to have a couple of such barramundi.'
Therefore, several weeks later the Sidney museum got a barrel delivered by the mail carrier, and in the barrel were the fish, strongly salted.
Craft literally froze when he saw them. Forster was correct: the fish were completely unbelievable, and they had only four fins. All on their belly. And all looked rather like flippers. And the tail was very peculiar: not forked, as in many fish, but wedge-shaped. The zoologists call tails of this type the diffecircular. This, perhaps, is the most ancient form of fish tails.
But the biggest surprise awaited Craft when he looked into the fish's mouth. He saw on the up-per and lower jaws plates made of teeth fused with each other (4 above, 2 below).
Paleontologists encountered such rasping teeth among the fossils for a long time, but none of the living fish had them. Professor Agassiz, a big expert on fossil fish called the owners of such strange teeth ceratodes, meaning 'horn tooth'. 400-200 MYA they inhabited the waters of our planet.
And now Craft held this ceratodus in his hands! He decided so, after closely examining the fish's teeth, and therefor without a doubt called the Burnette salmon the ceratodus. Later, paleontologists discovered not just teeth, but the skulls of the truly extinct ceratodes, and they proved to be not quite the same as that of the Burnette one. Therefore, the ichthyologists offered to add to its scientific name the specification 'neo' (i.e. 'new') or 'epi' (i.e. 'after'). However, more often, the barramundi is still called just the ceratodus or the horn-tooth without any specifications.
While studying the fish, Craft cut open one of them and found inside of it something even more astonishing... a lung! A real lung. The fish had gills, but also a lung. Hence, this fish breathed with both gills and lungs, making it a lungfish.
Before Forster decided to visit Sidney's museum, zoologists knew only two lungfish: the South American and the African lungfishes.
The South American and the African species have two lungs, and the Australian lungfish only one. The South American and the African species are closely related to each other. The ichthyologists united them into one order - the Lepidosireniformes. The fins on their bellies and chests are not 'flippers' as in case of the Australian lungfish, but dexterous, thin 'tendrils'. The Australian lungfish, as described by Craft, is a member of the second order, the Ceratodontiformes.
The Australian lungfish lives in slow-moving rivers, overgrown with water plants. They lie on the bottom, slowly crawl around, pushing against the bottom with their paired fins, slightly bending out the back in the manner of some caterpillars. They are not shy; the Australian lungfish can be caught by netting the lazy fish by hand. After every 30-50 minutes the Australian lungfish surfaces and putting its nostrils out of the water, (in the lungfish anatomy - the choanas), with a loud dense 'groan' it inhales the air. It is supposed that the Australian lungfish cannot manage without air breathing even in oxygen-rich water.
However, the Australian lungfish that lived for some time in the Berlin aquarium, according to the director and the staff, never surfaced to breathe air.
In the drought, when their native rivers dry out, the Australian lungfish do not burrow into silt. They crawl there, where moisture remains under the shade of shrubs, where's shadow and the sun is not so burning. They gather at the bottom of deep river pits and breathe, breathe... with their lungs. But they cannot last long like this. In big droughts the Australian lungfish die. And when the fate is kind, they live long - up to 60 years! And grow up to 2 m. Then they weigh-in at 50 kg.
'The Australian lungfish eat almost exclusively animals, primarily snails, but plants too, but they can adapt to eating only animals' (Hans Fry).
The Australian lungfish lay large eggs onto aquatic plants.
In 10-12 days the eggs hatch. The larvae lack external gills (the South American and African species have them). The eggs of the Australian lungfish are not sticky; therefore, birds do not carry them from one body of water to another, as they do with the eggs of many other fish: the Australian lungfish cannot use the 'air route'. Yet humans, worried about the fate of the rare fish, which survive only in the waters of the Burnette- and Mary-River, took and released them into some other Queensland waterways.
The African lungfish live in the overgrown, slow-moving, swampy rivers, but their most common and multiple settlements - in the lowlands that get flooded by rainwater for several months a year. When they dry out and the ground is covered by only few centimeters of water, the African lungfish dig burrows. The fish sucks silk - takes it into its mouth and spits out from the gills. Beneath the silt, it soon reaches the dense clay: the fish chews it; the bitten-off piece is ground and then exhaled with the water through the gills. The tiny pieces of soil float upwards in a murky cloud and then settle around the burrow. A ride forms around the entrance. When the burrows is finished, (with a 'bedroom' in the depths - a pear-like widening of the tunnel), the African lungfish will settle in it bending into two: with the end of the tail and the snout pointing upwards. It breathes, inhaling water and also soil that was extracted from the burrow and settled in a ridge around it: this forms a cork that plugs the entrance. The skin of such concealed African lungfish is plentifully slimy. They say that slime forms a cocoon around the fish - a very thin film: hundreds of an mm! Only where the mouth is located, the cocoon has a small hole for breathing.
"In this cocoon, as the experiments have established, African lungfish can live up to 4 years. During the hibernation the African lungfish shrinks in size and weight, at that the musculature of the fish is used up for energy needs' (Kurt Dekkert).
When the rains return, (after 6, or even 9 months), and the stone-hard silt gets moist and soft, the African lungfish emerges from the burrow.
At first it swims clumsily, its fins that got unused to moving gradually straighten and strengthen. These chest and belly fins, which resemble long whiskers or whips, the fish has the taste organs. By examining and sensing with them the murky waters, the dense underwater vegetation, the African lungfish learns without questions, what is edible and what is inedible. And reacts accordingly.
The spotted African lungfish in hibernation 'preserves' itself (in silt and the cocoon) only in the driest years. Usually in the Congo Rivers, where it lives, the swamps rarely dry-out completely; ground waters remain under the silt. In June - July, when the water level of rivers and swamps drops sharply, the male of this species digs a burrow on the bottom. Then it brings a female there in a manner still unknown to science. The female lays eggs and leaves, and the male guards the eggs and later the fry. The water leaves, the bottom, where the burrow was dug, can become revealed completely, but the spotted African lungfish and its offspring survive, (the male has the foresight to dig a mine from the nest chamber to the ground waters to provide water for the burrow). In the rainy season the new water frees the male and its' young from their underwater prison.
The other African lungfish (marbled, gilled African and West African) breed during the rainy season. About in a month after leaving the burrows.
The male digs a burrow in the shallows amongst the dense and tall vegetation: a horseshoe-shaped tunnel with the two entrances on the ends. In its' depths - a nesting chamber, with eggs: up to 5000 of them, usually from several females.
'Since the nests are made in the shallows, so to reach the deeper waters the African lungfish make peculiar 'paths', squishing and pushing aside the dense vegetation... Often these 'paths' go for several meters, and when the water level sharply drops... then the African lungfish have to reach water over dry land... The male cares about the nest and the young by itself. It... powerfully bites anyone who dares to approach it, does not back away from humans either, (the natives are afraid of its furious attacks). Even if it is chased out of the nest with a stick, then it fearlessly returns after several minutes' (V. M. Makushok).
The African lungfish can crawl on land as well as the river eels do. The marbled lungfish supposedly does it during the days when it is not weighted down by caring about the young. It leaves for the waters for the riverside silt and the nearby grasses apparently to feed on the small members of the wildlife of those lands. The experiments have shown: it gets only 2% of oxygen that is needed for breathing; the lungs give the other 98.
By sexual maturity the marbled African lungfish reaches 2 m, and the gilled - only 44 cm. The other species, the spotted and the West - about 100-130 cm.