Sovereign of Fourseas

 

Tour to Neocene

 

26. Sovereign of Fourseas

 

 

 

The climate of Neocene epoch had become milder, than in Holocene. The part of continental coasts had become hidden under water, the bottom of ocean here and there has risen, and the level of ocean has a little increased. It was has the big influence at the features of climate - it had become much more damp, than earlier. The abundance of rains has caused displacement of borders of natural zones - areas of deserts has become strongly reduced, and the area of deciduous forests has extended. In equatorial belt of the Earth damp rainforests now are dominating, and some plains in large river basins have turned to extensive bogs. The increase of amount of rains has caused occurrence of large lakes and rivers. And the most impressing result of climate changes has become occurrence in Eurasia the huge saltish reservoir - Fourseas.
20 million earlier of this time the ice age radically has had an effect at the geography of southern and southeast Europe: Mediterranean and Black seas, cut off by tectonic processes from Atlantic, had dried up and had turned to small hyper-salt reservoirs among extensive salt plains. But with increase of rains amount these barren landscapes have come to life. In the Mediterranean the system of salty bogs, on which the original animals who have adapted for so extreme conditions live, was stretched out. And the Black sea is again full of water and life though the history of its settling is more dramatic.
When Bosporus and Dardanelles straits were closed as a result of movements of Earth's crust, and Asia Minor had collided with Europe, the Black sea had turned to an isolated from the ocean reservoir and had mostly dried up. Shallow sea of Azov had dried up even faster. The area of Caspian sea had been strongly reduced, and Aral sea had turned to small similarity of the Mediterranean - barren salty plain.
But in a Neocene the situation began to change for the better. Rains have filled in the Caspian lowland, and soon Caspian sea has merged with Aral. In estuaries of rivers inflowing into Caspium sea, some of species of the animals, capable to exist in conditions of changeable salinity was kept. They have got rather favorable chance for development, again having occupied the formed sea lake with very low water salinity level. The sea was occupied even by descendants of freshwater species. And the species of Black Sea was unlucky: the rivers of the Black Sea basin have dried up during the ice age; therefore there are nobody to occupy sea again filled by water - except for bacteria, protozoans and several species of plankton crustaceans and algae, in the new Black sea nobody had lived. But then big trouble has happened: strongly spread waters of the Aral - Caspian basin have reached the Black sea and both basins have united. New huge reservoir waters have formed, filling pools of four seas - Black, Azov, Caspian and Aral seas. Association of pools had caused leap of salinity because in hollow of the Black sea the huge amount of salts had been accumulated. Besides reservoirs at the area of Black sea are rich in sulfides and hydrogen sulphide – it was the heritage of Holocene epoch. The Black sea was deep, but waters of it have mixed up poorly, that has caused occurrence above a bottom of practically lifeless water layer. Such "heritage" had became a problem for the species not resistible to salty and dirty water. Someone from their number had receded in river mouths, some species had died out. When position was stabilized, set of staying empty ecological niches had formed, which had been filled by descendants of the survived species. Gradually new reservoir appeared populated as plentifully, as in Holocene epoch.
In a Holocene at the African continent there was few Great African lakes, which numerous fish population belonged mainly to cichlid family (Cichlidae). Other groups of fishes inhabited these lakes, were less various, than cichlids. In Fourseas the situation has practically repeated, with the only difference: instead of cichlids gobies (Gobiidae), capable to endure changes of water salinity, have became main group of lake ichthyofauna. Some species of this group have survived in estuaries of the rivers at the integration of Black and Caspian seas, and have become ancestors of fishes of Fourseas.
Waters of Fourseas numerous species of the diverse gobies inhabit. Some of them live in thickets of plants, others live in water thickness or prefer to settle at the bottom. Small gobies eat invertebrate animals, and larger species are predators. The most numerous inhabitants of local waters, crustaceans, serve as food for many species of fishes of Fourseas. Herbivorous fishes are rarity in Fourseas, and their ecological niche was strongly occupied with various species of crustaceans – scuds (or side-swimmers). The majority among side-swimmers includes plankton species, filtering unicellular algae in thickness of water, but also the large forms eating macrophytes are present. These species keep in estuaries of large rivers where in water of poor salinity carpets of eel grass, pondweed and cane spread. But the coastal zone is richly populated with gobies of different species, the majority of which is not squeamish crustaceans.
However even the most gluttonous and ruthless hunters among gobies try to keep closer to saving bottom and hide in more rich thickets when above sand and stones the ominous shadow of seven-meter predator has sliding. Lazily moving by huge crescent tail, the monster swims above thickets of plants. Long leaves of eel grass and pondweeds wave from the waves spreading at movements of huge creature. The small weak-sighted eyes located on each side of flat head, will hardly notice fishes hidden in plants, but long wattles, supplied by organs of chemical feeling, will give the full information about those creatures which cannot be seen. The beams of the sun penetrating thickness of water, slide on each side of the monster, decorated with longitudinal lines of osseous plates.
Such visitors seldom come deep into coastal thickets, preferring to keep in open sea. This creature is the tsar-fish, the representative of the sturgeons becoming rarity in Neocene. Here, in Fourseas, not having adequate competitors from among sharks and osseous fishes, sturgeons have survived in plenty. And the tsar-fish occupies a place of honour at top of an ecosystem, gathering its share in populations of gobies.
Having swum among coastal thickets, the tsar-fish turns off in the high sea. Gradually at the bottom under its stomach thickets of plants vanish, and then the bottom is lost somewhere below, covered by thickness of water. Absolutely other world - the world of plankton, the basic productive zone of Fourseas here begins. Here, far away from the rivers carrying in the sea dregs and silt, in transparent water microscopic algae sometimes coloring water greenish color grow in huge amount. And here the food chain, which tsar-fish crowns by itself, begins.
Plankton algae breed with improbable rate. Especially they are plentiful in areas where the rivers carry out in the sea plenty of mineral and organic substances which are washed away from ground. But other centre of variety of plankton sea algae is the high sea where there are good conditions for growth: no oozy suspension in water, constant salinity and intensive sunlight. Breeding with constancy and regularity of clockwork, algae can fill by themselves all top layer of the sea. But they never will make it, because the significant part of them will be eaten by tiny inhabitants of thickness of water.
The most usual plankton animals of Fourseas are midgescuds. These crustaceans continuously filter algae with the help of the mouth legs covered with bristles. Breeding in plenty, they do not give algae to expand widely. The crustacean spends the most part of life, soaring in thickness of water. It is little bit heavier than water because of massive shell, therefore from time to time it is compelled to move by legs to immerse not so fast to bottom layers of water. Usually it simply places long legs in sides, and soars in water, as if the small jellyfish. On legs of the crustacean there is the set of sensitive bristles which give it the information about the movement of water around. It is very important - in plankton not only vegetarians meet.
Midgescuds form large rich flights: in one liter of water up to 80 - 100 crustaceans of different age may be. Such congestions drift to tens meters, mounting two-meter thickness. Usually crustaceans are inactive, but sometimes their flight comes in chaotic movement: crustaceans skip to sides, randomly bumping with each other. It means only one thing: the attack of one of plankton predators. If to look attentively, it is possible to see in water completely extremely appearing creature with the body of dragonfly, long head, the branchy antennas similar to ragged wings, and one large eye in the middle of forehead. Appearance makes clear that this creature is the cladocer crustacean. This creature is twice larger than scuds, and its jerky movements are the evidence of that it is a predator. Usually strange creature soars in water thickness, drifting by current. But when in its field of view the catch appears, the tiny monster quickens: it aims by cautious movements of antennas at catch, and then by quick throw overtakes the prey - usually young scud or fish fry. Ruthless jaws pierce in prey body and instantly terminate it. The manner of hunting very much resembles habits of the hawk: this creature also is named as the hawk leptodora. It is the descendant of one of species of Leptodora - the large predatory cladocer crustacean from fresh waters of Eurasia.
The hawk leptodora slowly devours catch - the young midgescud. The life of leptodora in Fourseas is not bad - this species is significantly larger that the ancestor had been only one centimeter long. But nevertheless it can easily fall prey to other plankton animals. In plankton not only crustaceans live – larvae and fry of various gobies make a significant part of plankton. All of them have fantastical shape: their fins are decorated with the various outgrowths, allowing soaring in water thickness. Larvae of gobies eat different infusorians and microscopic worms - rotifers (Rotatoria), forming nannoplankton - the smallest plankton. Larvae of gobies are inactive - they wait, while catch itself will swim up right to the mouth. Then there follows the quick throw - and new expectation. Small mobility allows saving forces, in this case the most part of nutrients is using for growth of the organism. But it is fraught also with rather unpleasant consequences: predatory crustaceans are not asleep.
Light is shimmering as the rainbow in spherical eye of the transparent hawk leptodora. The crustacean recently has finished with the next prey, and now it looks for new catch. Sight at the hawk leptodora is not so good - the crustacean is short-sighted, but at the distance about 10 - 12 cm it confidently distinguishes alive creatures fifth part of its own size long. When near soaring leptodora the transparent larva of the goby floats, the crustacean badly sees it, but organs of chemical feeling give out to the predator the location of prey. Fast throw - and the larva writhes in prickly legs of predator. Having got hold of the next dinner, the hawk leptodora begins the meal. By sharp mandibles it divides into particles meat of catch, and then eats turned out gruel.
On the back of the hawk leptodora there is the large egg bag in which through transparent walls about one and half tens eggs are visible. After 10 - 12 days from them the new generation of gluttonous crustaceans will hatch. To tell the truth, few of them attain the maturity - the majority, alas, will be eaten by adult neighbours.
For one day the large hawk leptodora devours about 80 fry or ten adult midgescuds. But also it did not become the king of predators among plankton animals. In plankton of Fourseas there are fishes - glass-transparent plankton gobies. Though they are only a little larger than the hawk leptodora, but surpass it by might. Jaws of the plankton glass goby are armed with the sharp thrust teeth easily piercing fragile shells of leptodoras. Gobies are practically transparent - only dark eyes and peritoneum through which sun beams do not pass, indicate their location in water thickness. Other organs and tissues of the animal are completely transparent. Such transparent fish lived in the Asian tropical reservoirs of Holocene epoch – it was the glass catfish (Kryptopterus bicirris). Therefore it is quite possible for fishes to become the phantom - the invisible being.
Having noticed the hawk leptodora, the glass goby comes behind to not be noticed and at the same time to avoid sharp mandibles of the crustacean. Carefully having aimed, the small fish makes throw, trying to put the sting to the pleon of catch. After the attack the goby does not turn loose the "bulldog" bite, expecting while the hawk leptodora will die. Having convinced, that tenacious legs and sharp jaws of predator do not threaten to it any more, the goby starts to devour catch. More often it limits itself to tearing off and eating the pleon and eating away the contents of thorax of the crustacean. Having filled a stomach, the glass goby slowly continues to soar in water, having stretched wide fins. It accumulates fat for the most important event in life – for spawning. Only once at life this small fish can spawn and hatch fry. At females almost all nutrients will be transformed to the portion of large eggs, and the body of the male to spawning time changes by strange way: jaw bones extend, the mouth expands, teeth decrease. The mouth of the male turns to the true mobile incubator where fry are carrying. In shoals of plankton it is possible to see the “large-headed” males busy with egg bearing. They strongly grow thin, and it seems, that the head is attached to the fish obviously “not according by the size”. In mouth of such males the precious laying is incubating. Felt the leptodora presence near to itself, such male does not attack any more, and tries to swim out, carrying away eggs. In rest the male “being in the family way” regularly ventilates eggs, driving water through semi-opened mouth. Through walls of mouth it is possible even to observe, how eggs are incubating, larvae move in a mouth of the daddy and turn to the fry ready to independent life.
All time while fry are in the mouth of the male, it eats nothing, supporting self-existence due to the nutrients saved up in the organism. Fat in the beginning is using, then the gland and the intestinal tract reduction begins, and at last stage muscles of its body start to atrophy.
Fry in the mouth of the male grow simultaneously - they emit the chemical substances synchronizing development of hatch. And one fine day from the opened mouth of the father the true school of fry ready to independent life comes up. At the moment of fry going out the male turns to real “living mummy”. Changes in its body are so great, that they become absolutely irreversible. Having executed the duty to the future generations, the male perishes. Plankton midgescuds and … hawk leptodoras, which have no objection to diversify the ration with carrion, wait for this moment.
The big congestions of plankton in the high sea involve rather large fishes eating water smallness. The high sea is inhabited with schools of large gobies, evolved to pelagic habit of life. They pursue driven by wind and waves shoals of plankton crustaceans and fry, eating only them. Pelagic silvergobies swim in the big schools - up to hundred ones and more. From afar their silvery colouring makes them practically invisible on the background of sea water, and the cloud of plankton still worsens visibility, in addition protecting gobies.
Having found out the congestion of plankton, silvergobies begin hunting. They open too much wide mouths and spread operculums wide. Branchial arches of fishes turn to the original plankton net filtering large zooplankton. Midgescuds, leptodoras, glass gobies - all these creatures get in this mouth-trap. The silvergoby moves by tail, swimming through the cloud of plankton. Thus its pectoral fins are opened like fans, assuring balance and elevating force.
On bodies of some gobies tiny long-bodied small fishes sit – they are gobies too: bellysucker gobies. Their abdominal fins have turned to very powerful sucker, safely keeping them on the body of the chosen host. The bellysucker goby clears the body of the host fish from parasites, receiving thus the opportunity to move freely together with silvergobies. And during the feeding of the host fish the bellysucker goby can regale itself too not bad: for any seconds darting off from the body of the silvergoby, it catches large crustaceans swimming near the mouth of the host fish. While the host fish does not hunt, the bellysucker goby can even get to it into the mouth, accurately clearing gills from parasitic crustaceans and worms which infect silvergobies with the help of plankton larvae.
The school of silvergobies finishes feeding. Fishes accurately close mouths, from time to time moving by the bottom jaw from side to side - so they pack up the trap organs. Having folded pectoral fins, the school of fishes is swimming near the surface. The sunlight transforms their bodies to inexpressive flat silhouettes invisible from afar. But swimming fishes are given out with the fluctuations of water spreading from school of gobies far away. And sensitive organs of one inhabitant from Fourseas have marked this school.
Almost eight-meter long tsar – fish, slowly swam through thickness of water, has quickened, when cells of its lateral line have felt movement of fish school. Though it would not see gobies, even they had swim twice closer to it, the lateral line has precisely prompted to the fish the direction and provisional distance up to the school of prey. The long crescent tail has struck on water, and the lazy creature had turned to the live torpedo. Had gathered speed, the tsar – fish, as if the battering ram had ran to school of silvergobies. Its toothless mouth has widely swept open, having grabbed at once some large fishes, and then have promptly slammed. There is no sense to continue attack – the school has swum out, and hunting for single fishes is energetically unprofitable. The attack has taken only some seconds; after it the tsar-fish has again found greatness and calmness of movements. In water at the place of swum out school of silvergobies the bellysucker goby, unhooked from the host at the attack of predator, lonely scurried here and there. And it has no other way, except for to go down to the skin of the huge armored fish and to stick strongly to one of plates on predator’s body.
Tsar-fishes not always live in the sea - once a year they rise upwards in the rivers where at the pebble shallow waters spawning rituals of giants take place. Eggs are buried in pebble and some days develop in relative safety from large fishes. And tiny larvae and fry of tsar-fish get in the world full of dangers. Millions of them perish literally in the first months of life, becoming prey of fishes and water insects. But the survived ones can live a long time - from above one and half hundreds years.
The young growth of tsar-fish grown to length 5 - 6 cm (after 1-st year of life) migrates down in the sea and first time keeps in the freshened shallow waters overgrown with water plants. Fry of tsar-fish are fattened by small scuds and larvae of insects, and pass to feeding by fish fry later. But while they are small, they represent the delicious dish for local predators.
Sandy shallow water is habitat of set of worms and larvae of mosquitoes. The tsar-fish fry finds them, cautiously investigating the top layer of sand. It literally touches sand by wattles supplied with set of chemoreceptors. And at last the fry feels something edible: under sand the red larva of chironomid midge moves. The fry picks up the portion of sand by long snout, and throws it up. From the cloud of silt and sand at once few larvae jump out. Wriggling and writing out "eights" in water, they vainly try to rescue themselves, but the small fish quickly catches them all. The frightened away scud also disappears in stomach of young predator. However the external calmness of landscape can be deceptive: the enemy has nearby hidden, and it waits, while the fry of tsar-fish will swim up more close. From sand pair of attentive eyes, turning after each movement of planned catch, sticks up. And when the fry unfortunately swims up too close, the shallow as if blows up: the flat head appears in cloud of silt and sand, the huge mouth opens, and the current of water literally sucks the fry in. Sharp teeth seize prey, not giving it the chance to rescue. Having swallowed catch, the invisible predator leaves the shelter. From sand the huge wide head, long trunk with big wing-shaped fins, and long tail appear. It is the stargazer sandgoby: its eyes are shifted upwards, allowing the fish dug in sand to look for catch. The fish about meter long slides above the bottom, flapping by pectoral fins, as if by wings. Having found the new place for the ambush, the fish falls on sand. Had crept a little on it, the fish digs in it by lateral movements of body, and then throws on itself sand by fins. Soon silt settles on the bottom and nothing gives out presence of predator. Only behind eyes, sticking up from sand, the sediment layer waves, when the fish quietly takes water in the branchial cavity and cautiously lets it out. The trap is placed.
The half meter long youngster of tsar-fish swims above the sandgoby laying in an ambush. But the predator will not attack: such catch is rather large for it. And in thickets of pondweed other hunter is hidden which is not to be averse to attack the young tsar-fish. The zandergoby is an inactive predator, as well as the majority of gobies. Due to the large size and the special anatomy of mouth it can eat large fishes. And the young tsar-fish is not too tough to it. Goggled eye the zandergoby observes the young tsar-fish engaged in search of scuds and worms. Swimming above the bottom, it as if touches by wattles sand and silt. Eyes of the fish look upwards and in sides, but wattles give the full information about the hidden animals. From time to time the fish rushes on the bottom and takes from sand the next scud or the wriggling mosquito larva. When the large scud runs away from a tsar-fish by jumps, it swims up too close to thickets of pondweed in excitement of pursuit.
Reaction of the zandergoby is momentary: it rushes out from an ambush and catches the young tsar-fish across the trunk. However almost at once it sets catch free: the young tsar-fish is densely covered with armour of osseous plates, and the predator simply at once had broken some teeth. And the young tsar-fish has not suffered almost: one of teeth has put to it an insignificant cut at the stomach. In some days the wound will skin over.
Usually the gobies of other species not protected by shell serve as the catch for the zandergoby. It hunts in coastal zone, and at times after storm it has plentiful catch “on the dinner table”. The next storm have brought to the coastal zone strangers from other ecosystem: school of pelagic silvergobies. Silvery creatures look completely inappropriate in green-brown-yellow world of shallows and thickets of plants. It had fallen to their share quite enough: at some fishes scales are scratched, magnificent fan-shaped fins are tore off, on bodies of several fishes there are deep grazes. Silvergobies are scared by unusual conditions: they press close to each other, forming dense globe-shaped congestion. Their sides brightly sparkle in sunlight, giving out to predators the location of fish school. And predators do not keep long waiting: from greenish haze the monster appears - adult, approximately six-meter long tsar-fish. It heads straight to school of silvergobies. The huge mouth opens, in it at once three fishes disappear, and the monster departures. But gobies do not swim away, as it would be in the high sea. Disoriented by unusual conditions, they gather to sphere heads inside even more densely. But the tsar-fish, as against these gobies, feels like at home both in the high sea, and in coastal zone. And it uses the moment, coming back to school of gobies. Attacking more and more times, it orderly annihilates pelagic gobies. Eventually from flight only one fish had remained in panic rushing here and there. At last it rushes to thickets... where its head immediately ended up in strong bite of zandergoby’s jaws. Sharp teeth easily stab skull of the silvergoby, and catch of the zandergoby instantly dies. The predator starts to swallow prey orderly. Its jaws alternately move fish body in wide gullet, hooking it by teeth located on the palate and jaw bones. Gradually catch takes the place in stomach of the zandergoby, and the predator hides more deeply in thicket. Certainly, it is still a predator, and the majority of fishes will be afraid of it. But in the sea there are such fishes that are afraid of nobody...
The tsar-fish, slowly moving by tail, swims above the bottom. Tips of its long wattles feel bottom in searches of edible creatures. More and more clearly the huge fish feels the smell of catch, however its small eyes see only few fry of any goby swam above the head of giant. And they obviously do not correspond to the smell which is felt by fish. Catch is somewhere beside, but it is hidden. Some shrubs of plants waving near to the tsar-fish, can not hide large catch. It means, that catch is somewhere under sand. And the tsar-fish starts to dig it by lateral head movements. Literally at once from sand the large sandgoby rushes up, up to last moment not leaving the shelter. Flapping by pectoral fins, the fish tries to swim away, but the huge predator right here overtakes the goby, presses to bottom and snaps it. Having crushed catch by jaws, the tsar-fish re-seizes the goby from the head and swallows. Few seconds - and all is over. The silt lifted by short fight of fishes slowly sediments on the bottom. And the tsar-fish majestically leaves to the high sea.
Gradually the bottom starts to revive: scuds dug in sand move, tiny gobies swim. And above thickets the young tsar-fish swims. While it is still small and easy can become the anybody’s catch, but twenty years later all live beings will hide and freeze horror-stricken when it will visit this area.

Bestiary

Midgescud (Planctopulex chaetognathus)
Order: Amphipoda

The pelagic representative of order Amphipoda. Length of its body is about 1.5 cm. This crustacean filters phytoplankton, breeds plentifully in water thickness, forming large congestions. The animal eats with the help of mouth legs covered densely with hairs. With the help of fleshy blades in the basis of mouth legs the crustacean creates constant current of water through hairs of mouth legs. Thus cells of algae and protozoans stick to them. From time to time the crustacean scrapes by mandibles food gruel from mouth feet and swallows it.
The crustacean spends all life in plankton. It soars in thickness of water, having stretched legs covered with hairs. Hairs serve to slow down immersing of the animal, and also serve as sensitive organs, allowing the crustacean to trace movement of environmental water.
Diecious animal, but in the summer at the increasing of water temperature frequently passes to parthenogenetic breeding. Eggs (up to 200 ones) are carrying in brood pouch on the bottom side of the female body. Alternation of generations occurs quickly - during 4 weeks the larvae hatch from eggs, stay in brood pouch of mother and go out in water. Within 3 months the crustacean becomes the adult and breeds at first time. During the life the female can make up to 10 clutches 2 months apart.

Hawk leptodora (Macroleptodora accipitrina)
Order: Phyllopoda

The representative of cladocer crustaceans (order Phyllopoda, suborder Cladocera). Length of body is up to 3 cm. Body is translucent; it seems, that the crustacean is made of glass. Through covers of body internal organs are perfectly visible. Sight of this animal is perfectly advanced, though there is only one large complex eye at the forward part of head. This is predating species, attacking crustaceans and fish fry; for day it eats as much food, as it weights itself. The animal spends the most part of time, soaring in thickness of water, but for prey capture it is capable to make sharp throws. Long legs and two spikes on the end of pleon facilitate soaring; the animal quickly swims with the help of movements of the huge oar-like antennas covered with hairs. It seizes catch by large forward leg pair covered with bristles from within.
Significant part of lifetime the crustacean breeds parthenogenetically, males appear only in extreme conditions (cold snap, increase of water salinity in the closed bays). Eggs are carrying in brood pouch on the back side. Larval stage lasts 8 days, general life expectancy is about 1 month. The significant part of larvae perishes as the result of cannibalism of adult individuals.

Stargazer sandgoby (Astrogobius arenarius)
Order: Percoid fishes (Perciformes)
Family: Gobiidae

Picture by Lambert

Initial picture by Pavel Volkov

This large species of gobies (Gobiidae) is the benthic ambush predator. Length of the body is up to 1 meter. Appearance of this creature is rather strange: the fish resembles the usual goby strongly stretched in width. Head is large (about 1/5 of general fish length), eyes are small. Wide mouth and eyes are revolved upwards (by this feature the fish resembles Holocene stargazer fishes (Uranoscopus)). Operculums are revolved on the top side of the body, from sand they are protected by the skin plica. That the fish free could breathe, the plica at the top part of operculum forms the respiratory tubule through which water is sucked in branchial cavity at the closed mouth. If to look at the fish hidden in sand, it is possible to see, how from sand pair of short skinny tubules sticks up, and around them sand from time to time distend and falls down - it is the water accurately pulling out from the branchial cavity. Pectoral fins are wide, fan-shaped. With their help the fish buries in sand and throws it on the body for masking. Abdominal fins are short, with overgrown bases, helping the fish to be dug in sand. The prickly back fin is separated from soft one, in the basis of spikes there are well developed poisonous glands. Body is flatten, caudal peduncle is long and thin, tail fin is narrow. The fish moves basically due to waves of pectoral fins, during swimming resembling the ray. Coloring of the body corresponds to environment in which the fish lives: the top side of body is colored sandy yellow with small brown speckles, bottom side is grayish white. The male differs from the female by larger size, wide head, graceful body and wider prickly back fin which basis is colored black color and is bordered by narrow white strip.
Spawning takes place in sea shallow waters, the male incubates eggs (up to 100 - 150 large grains of roe) in mouth within 2 weeks. The young growth 2 days stays in mouth of the male, when the yolk sac will resorb. The generated fry about 1 cm long leaves the male for ever and further live independently. At 4-years age at length about 60 cm the fish becomes adult and is able to spawn. Live duration is up to 15 - 18 years.

Zandergoby (Luciogobius stizostedion)
Order: Percoid fishes (Perciformes)
Family: Gobiidae

The ambush predator of the family of gobies (Gobiidae), ecological analogue of pike perch and pike. Length of the body is about 80 cm. Body is rather high: the height is approximately twice more than width. Mouth is wide, in it there are large slightly recurved teeth. Mouth cut is slanting, corners of mouth are lowered downwards. The jaw anatomy allows to push the caught prey in gullet by alternate advance back moving. Fins are wide, back and anal fins are shifted back to tail. The prickly back fin is submitted by the several short spikes connected by reduced membrane. Coloring is cross-striped, on grey background there is the pattern of vertical green strips and brown speckles – it corresponds to color scale of underwater plant thickets - the favorite shelter of fishes. At males the membrane, connecting jaw bones, is painted red color. When the fish closes mouth, this coloring is not visible, but in spawning season one of elements of courtship ritual is the demonstration of bright membrane.
Fish keeps in thickets of long-stalk plants, trapping and seizing catch by throw. It can catch fishes of the size comparable to itself, eats them due to an extensible stomach.
Spawning takes place in thickets of water plants. The male and the female clear from silt and dirt the flat stone on which eggs are spawned. The female protects clutch, fanning it with movements of fins, the male protects territory around of the clutch, sometimes substituting the female.

Pelagic silvergoby (Argentogobiosoma pelagica)
Order: Percoid fishes (Perciformes)
Family: Gobiidae

Large fish of family of gobies (Gobiidae) - length of body is up to 50 cm. It inhabits thickness of water, not swimming to the bottom. Wide pectoral fins and very fat liver facilitate to the fish soaring in water. The body is lengthened, slightly compressed from sides. The head is large (till 1/5 of general length of the fish), but the most part of it is occupied by the complex filtering system of overgrown branchial edges with which help the fish filters zooplankton. Teeth are thin, hair-looking, very numerous - they "lock" mouth, not allowing catch to swim out. Eyes are large, slightly shifted to the top part of head.
Coloring is soft: body is silver-gray with bluish shade, back is darker. Such coloring is typical for fishes of thickness of water. Pectoral fins are wide, fan-shaped and translucent. Unpaired fins are wide, in the first back fin there are three poisonous spikes. The tail fin is high - fish can swim quickly, escaping from enemies.
The spawning takes place in thickness of water, the male incubates eggs in mouth. In clutch there is up to 200 small eggs. Larvae spend in mouth of the male about one week, later they pass to independent life. The larva looks originally: unpaired fins merge together, "bordering" the body. They are very wide - more than height of body. It facilitates soaring in water. The larva eats algae, later - protozoans and zooplankton. At the age of 3-month the development of filtering system and pectoral fins begins. Fish matures at 1 year, life expectancy is till 8 years. At the age of 3 years the fish grows to length 40 - 45 cm, later its growth is slowed down.

Plankton glass goby (Pterogobiops crystallinus)
Order: Percoid fishes (Perciformes)
Family: Gobiidae

This is tiny species of plankton fishes - length of body of the female is about 3 cm, the male is 3,5 cm long. Body is practically transparent, at the swimming fish at insufficient illumination only large eyes are visible. Intestines are shielded by shining lining of peritoneum. Against the light at this fish all bones and intestines are visible.
This species constantly lives in plankton. It doe not approach close to coast, preferring to stay in the central part of Fourseas. It keeps in water due to the plenty of fat in body - the density of body is equal to density of water. Soaring is promoted also by wide pectoral fins which rays are divided to 2/3 of the length, and the membrane has outgrowths as the fringe. The body of this fish is rather high, unpaired fins are wide. Spikes of back fin are strongly jutting out from membrane, their prick is poisonous. Jaws are strong, with long teeth in forward part. Teeth jut outside at the closed mouth.
Fish eats crustaceans and their larvae; sometimes it can attack even predatory crustaceans.
Spawning takes place only once a life. The female spawns eggs in mouth to the male and perishes after spawning. The male perishes after the fry hatching. With approach of spawning season the body of fishes changes: intestine degenerates, sexual glands actively develop. At males jaw bones expand, forming large brooding chamber for larvae. In clutch it is up to 40 large grains of roe. Larvae hatch after 3 days, but stay in mouth of the male about 2 weeks. Life expectancy is only 2 years.

Bellysucker goby (Echeneogobius striatus)
Order: Percoid fishes (Perciformes)
Family: Gobiidae

This small fish (body length is up to 5 - 6 cm), living on the body of large fishes, differs by the powerful abdominal sucker formed, as at all gobies, overgrown bases of abdominal fins. The body is the streamline-shaped, tail is very long. Unpaired fins are short, tail fin is narrow, abdominal fins are reduced up to small hooks - the fish is adapted to attachment to the body of large fishes, hardly swimming independently. Pectoral fins are wide, with strong fleshy bases. During movement of the host fish they help the goby of the present species to keep in stream of water. Eyes are small, capable to remove inside of eye-sockets when the host fish accelerates movement. Such feature well protects eyes of the fish from casual traumas. Coloring is golden yellow with black longitudinal strips on the back and along each side. Eyes are blue. The male is more graceful, large and "large-headed", than the female.
Eats the rests of catch of the host fish, tiny plankton organisms (fish catches it, leaving the host for some moments). Also the fish renders the host of service of the cleaner, gathering parasites even from eyes, gills and mouth of host fish.
The bellysucker goby spawns, bearing eggs and fry in branchial cavity. In clutch it is up to 50 grains of rather large roe. Process of spawning is very original: thus fishes do not leave the body of the host fish. The female spawns eggs in the mouth to the male, then the male transfers her spawned eggs from mouth to mouth and moves forward the female. It emits soft roe in water, and the female holds the position behind it to catch by mouth soft roe as much as possible. In the mouth of the female there is the fertilization of eggs which later are transferring to the male for incubating. The young growth stays in the mouth of the male up to resorbtion of the yolk sac (about 4 days), then they swim out. First few weeks of life the young growth spends in coastal thickets of plants, then searches for the host fish.

Tsar-fish (Pseudohuso cataphractus)
Order: Acipenseriformes
Family: Acipenseridae

It is the largest fish of Fourseas - the huge sturgeon fish growing to 7 - 8 meters long. This is the descendant of widely expanded and hardy species of sturgeons – the sterlet (Acipenser ruthenus). Due to short life cycle this species could survive in the changeable environment with strong anthropogenous influence.
Body shape is the characteristic form of almost sturgeon fishes - unpaired fins are shifted to tail, tail fin has almost equal lobes: the top blade is only a little longer than bottom one. The skin is covered with shell plates along ridge and sides. At young growth intervals between lines of plates are little (the shell is almost solid), it rescues fry from predators. The head is flat with long firm snout, allowing to dig out catch from sea bottom. The mouth is inferior, widely opening and toothless. Eyes are small, located on each side of head. Fish has long wattles on which numerous organs of chemical feeling are placed. With the help of wattles the fish finds food even in oozy muddy water or under the sand layer. The bottom side of body is almost white, top side is greyish green with slight cross strips.
The fish is active predator, young growth eats larvae of insects and worms. Later the fish starts to eat fry and small fish in thickness of water, the adult fish hunts large single and schooling fishes.
Spawning takes place in rivers, in clutch there are up to 5 - 8 million tiny grains of roe. Parents dig eggs in pebble and do not care of it any more. Fry the first year lives in rivers, later it migrates down in the sea. Sexual maturity at males is at 12 - 14, at females - at 15 - 17 years, to this time length of the fish increases to 3 - 3,5 meters. Life duration is up to 150 - 180 years, separate individuals pass also 200-year boundary.

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