Why are crayfish called orderlies of reservoirs?

To a beer or cold, foaming kvass, there is nothing better than a couple of boiled crayfish. For many, it is not so much pleasant to cook them or eat them, how to catch them, because this is a gambling and exciting business. Everyone knows that crayfish are called the orderlies of the reservoirs, but few people know why. The fact is that if crayfish live in any body of water, be it a river or a lake, then the water here can automatically be considered very clean. Cancers can live only in the purest and well-oxygenated water. Many lakes have problems with the latter, because crayfish still prefer the flowing water of rivers.

So these living entities are eating decay and carrion. They love to gnaw the carcasses of dead fish, frogs and other inhabitants of the reservoir and its surroundings clean. Thus, they help to maintain cleanliness in the water and can rightfully be called the orderlies of the water area. Everyone saw that if a fish dies in the aquarium and does not throw it away. It will begin to decompose, and the water will become cloudy. Soon all the inhabitants of the aquarium will rest. Roughly the same thing would happen in natural reservoirs, if there weren't such scavengers who regularly put things in order, maintain cleanliness and prevent the spread of decay processes and contamination of water and its inhabitants.

Moreover, if, for example, a living creature died due to some disease, then continuing to decompose in water, it will thereby infect the entire surrounding space, including all living beings nearby. But crayfish are able to digest literally everything, they have excellent immunity to decay processes and to many bacteria, therefore, even eating an infected fish carcass, crayfish do not harm themselves at all. In general, they lead a very active lifestyle, all the time examining the bottom of the reservoir in search of possible food. And thanks to this, they deservedly received the title of orderlies of reservoirs.

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Domyshev Egor 4th grade

The topic of the structure of the organism of fish, their characteristics and life in the aquatic kingdom, their observations and conclusions about the beautiful fish of their native land are revealed.

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MBOU "Tunkinskaya secondary school named after Sedov UP"

District scientific and practical conference

primary school students "First steps"

Nomination: Biology. Vegetable world.

Topic: "Pisces"

Completed by: Domyshev Egor

4th grade student,

S. Tunka, Green, 13

Checked by: Lobytsina TF

Teacher early. classes

year 2012

Introduction.

In the summer my dad and I went fishing. Sitting at this fascinating lesson, I thought about how the world of fish works. After all, I know almost nothing about them. They are distinguished by their color and body scales, their dexterity to stay under water, each fish is something amazing. And I decided to reveal more for myself the mysterious and wonderful world of fish. The purpose of my work: to find out what kind of science studies the structure of the organism of fish and their life, to be able to distinguish common features and variety of fish, to know what fish are found in the reservoirs of our region.

Main part.

2.1. It is interesting.

It turns out, reading the sources, I learned that there are about 200 thousand species of different fish on earth, more than frogs, newts, toads, salamanders, snakes, lizards, all birds and all animals combined!

Watching fishing, watching TV. I. Cousteau about the underwater world and its inhabitants, a very interesting TV show: "Fishing with passion" I was convinced that the sizes of fish are very different: from one centimeter to twenty meters. It has been noticed that in small reservoirs fish do not grow as large as in large ones. Of course, the Tunka River is much smaller than the Irkut River, therefore the fish in Irkut is larger. I had to catch the smallest fish - loach, 3 centimeters in size, and the biggest fish caught by my dad is burbot, 1.5 meters in size. Every fish has its own, special body shape, color and size. There are fish thin and long, like a whip, thick and round, like a ball, tiny - like an ant and huge - bigger than an elephant. There are herbivorous fish like sheep and goats, and there are carnivorous fish like tigers and lions. I found out that the largest fish is the whale shark (40t.). The smallest pandaka goby (1 cm). The fastest fish is a sailboat (109 km / h)

2.2 The organism of fish.

The body of almost all fish is covered with scales, like chain mail. Examining the scales of the fish, I noticed that some of the scales are wide, and some are narrow. It turns out that the fish grows quickly in summer - and the ringlet on the scales is wide, and in winter it hardly grows - and the ringlet turns out to be narrow. It turns out that by the rings, wide and narrow, you can count how many winters and how old the fish are. In my house, crucians lived in a home aquarium, and by observing, I was really convinced of this. And yet, it turns out that you need to change the water every day, and feed the fish with special food, from other food the water quickly turns sour, and this threatens the life of the fish.

Fish are perfectly adapted to life in the water. No wonder they say: "Fish are the children of water." Their bodies are streamlined, and this makes it easier for them to swim. Smooth scales, their streamlined body shape allow the fish to glide easily in the water column. Strong muscles bend the body of the fish forward in waves. The fins help her to maintain balance and slow down. The gills extract the oxygen needed for breathing from the water. The tail oxygen is necessary for breathing. Tail fin - the paddle moves the fish in the water. Fish have a swim bladder (no one except fish has one), which helps them to dive, emerge and soar in water. And even "talk". And then there is an amazing organ - the lateral line. It allows fish to see without eyes and hear without ears. In fish, on the sides of the body, under the skin, nerves stretch that perceive the weakest vibrations of water. They inform the fish about the approach of a predator or, conversely, prey. A person has five senses: sight, hearing, taste, smell, touch. And in fish - six: also a sense of the lateral line. The predator is not visible yet and not heard, but the fish already senses its approach - with its sides! They also find their prey by smelling - by smell. Odor-sensitive papillae are found in their mouth and on the face. Reading encyclopedias I learned -

The science that studies fish is called ichthyology.

The fish is adapted to the place in which it lives. Fish that have a lotand swim fast, - slender, streamlined. Those for whom it is more important to hide more securely, to be invisible, look like stones, algae, like clods of silt. For example: seahorses, sea needles, rays, gobies. The color of fish is also very different. There are white, black, brown fish. There are completely colorless, almost transparent. There are a lot of fish and multicolored ones: striped, speckled, speckled, zigzagged.

some fish change color like chameleons. Flounder on a sandy bottom turns yellow, on a silty bottom - gray, and on a stony bottom - spotty. There are fish that turn pale when scared and blush when angry.

Birds lay eggs and fish spawn. Fries hatch from the eggs. fish spawn in hundreds, thousands, millions. Most of our fish spawn in spring and summer - pike, perch, roach, bream, carp, catfish. Some spawn in autumn (salmon, trout), and even in winter (burbot).

Eggs ripen on algae, snags, stones. But there are fish that arrange special nests for caviar. The seahorse and the sea needle always carry their caviar with them, in a special bag on their belly. The fewer eggs a fish lays, the more it takes care of them.

There are viviparous fish: sharks, rays, eelpout. They hatch eggs inside the body and immediately spawn live fish.

And yet, most of the fish and eggs perish. But it would be much worse if a fry emerged from each egg, and a fish grew out of each fry. Then all the rivers, lakes and oceans would overflow with fish, and then it would all perish from the crowded lack of food.

2.3 Fish of our rivers.

There are two rivers flowing in our area - the Tunka and Irkut rivers. Our rivers are rich in fish: minnows, burbot, perch, soroga, dace, bream, crucian carp, grayling, taimen, linok, whitefish. You can also see pike. The fishermen called her the river wolf. She attacks both small fish and large ones, if hungry, she will drag a goose or duckling to the bottom. But the pike orderly has one more nickname. Indeed, first of all, pike attacks sick fish and thereby cleans water bodies, does not allow diseases to spread. There are many small representatives of carp: minnows, minnows, crucians. bream. Crucian carp is unpretentious. Can live in stagnant water. Eats everything. Bream - has a body flattened from the sides. It feeds on molluscs, worms, insect larvae, algae and plant shoots. Gudgeon - has a lumpy speckled body, greenish-brown on the back, yellowish-silver on the sides and abdomen, yellow eyes, gray fins. There is such a fish - from the salmon family - taimen, whitefish, lenok. The only freshwater fish from the cod family is burbot.

Conclusion.

I learned a lot about these amazing, beautiful creatures. In the future, I want to create a photo album "Inhabitants of the reservoirs of our region", I already have some photos.

It is not for nothing that the popular proverb says "Fish needs water, birds need air, man needs Motherland." In order for our rivers to be full-flowing, rich in fish, we need to take good care of them and their inhabitants. Of course, we are still small, but we can also contribute. While resting, do not litter the banks of reservoirs, do not throw garbage into rivers, do not destroy the flora of reservoirs, and fish only when permitted.

Literature.

1. "Fisherman - amateur" I.S. Forty.

2. "Life of the inhabitants of reservoirs" O.E. Zhirenko.

3. "The World Around Us" A.A. Pleshakov. Slide 7

PIKE is a river orderly.

Fish - water, bird - air, man - home.

We are ready to bet that everyone at least once heard that the pike is the orderly of the reservoir, have you wondered why? The pike is a predatory fish, and very voracious: it eats not only small fish, but also frogs, water rats, and even squirrels that swim across the pond. However, despite its gluttony, the pike, unlike the perch, for example, prefers not to chase after prey, it hides in ambush and waits until a fish swims nearby. At the same time, it chooses a weak and sick fish for attack, in fact, for this feature, they called it a "orderly", because destroying low-value fish, it not only contributes to natural selection, but also prevents sick fish from spreading the infection throughout the reservoir.

Moreover, for healthy fish, the danger from a pike is almost reduced to zero, if the fish leaves the throw, the pike does not continue the pursuit, it returns to ambush again. By the way, with the help of its teeth, the pike only captures and holds the prey, and does not chew, it swallows the victim whole. You should not get too carried away with catching pike, where this predator is destroyed, there will certainly be a breeding ground for mass fish diseases, the number of infected fish can reach 40-60%.

It is interesting that pikes live alone, choose a place for themselves and live there, in one place you rarely find two pikes of the same size, but if the place is suddenly vacated, another pike immediately takes it, and continues to clear the place of bad fish. Among other things, pike is a cunning, aggressive and cunning fish, therefore it is considered the main object of fishing among fishermen. After all, you need to have excellent fishing skills to catch this beautiful fish. And if you then cook fish soup from it, you will definitely understand that the pike is not only a medic.

My friend - an avid hunter and fisherman - recalled an interesting incident. Once, with a gun and a fishing rod, he spent his vacation time on one of the tributaries of the Poronai.

Small quiet river. Nearby there are oxbows overgrown with willows and bushes. I had to stand for a long time in the thickets, but the ducks did not sit down, the fish did not bite. It began to get dark. He was already about to reel in his fishing rods, but then a couple of teals flopped down on the lake quite close.

I could not resist, fired. The birds turned over and froze in the water. Suddenly one teal, lying on its back, rushed through the water.

Running closer to the shore, the friend saw that he was being pulled by a hefty pike. Without hesitation, he grabbed a spinning rod, quickly planted a small fish on the hook and threw the bait closer to the shot teal. The toothy robber immediately grabbed onto the tasty prey ...

Having gutted the fish, the friend was amazed: he found a beetle in its belly. The ferocious cannibal predator has swallowed her brother! A hungry pike mercilessly devours its young if the squids do not have time to quickly hide.

FISHING A FISH IN MURDY WATER

In the pike family, ichthyologists distinguish five species. The common pike lives in vast areas of Eurasia. Maskinong, striped and red-finned are overseas predators. They are found only in the waters of eastern North America, where they have always been a common food for the Indians. And only Amur pike is found in the basin of the river of the same name and here, on Sakhalin. About her - a special conversation.

Our compatriot, inhabiting calm rivers, oxbows and lakes, is somewhat inferior to her European sister, the common pike. The islander grows to a maximum of over one meter and weighs about a pound. She usually keeps near the coast. Only during spawning does it rise somewhat up the river or out into the floodplain during floods.

The pike is a cunning and terrible predator. It is not for nothing that it is called the freshwater shark. She also has some tricks. When hunting, the pike uses the following trick: it gets stranded with its head downstream and muddies the water with its tail. The mud hides it from the fish. All that remains is to open the toothy mouth and grab the prey.

Often it hunts from ambush, hiding among the water thickets, where it seems to dissolve. Like a chameleon, it can change color depending on the color of the algae and then, merging with the surrounding background, it becomes invisible. Having let the unsuspecting fish come closer, the freshwater vulture swiftly rushes at it.

Due to the fact that the dorsal and pelvic fins of the pike are shifted to the tail, it is able to make sharp throws. Surprisingly, the ferocious predator is able to chase fish even in the air, jumping high out of the water. Her jumps are amazing!

Possessing movable eyes, the pike sees almost as well both above itself and from the side. With the help of the lateral line, she feels the approach to various objects - to the boat, to the shore.

... FOR CARP TO DO NOT SLEEP

In rivers and lakes, pikes are caught both the wise gudgeon and the tiny minnow. In addition to fish, they consume any other living creatures that they can catch. For them, everything that has crawled into the mouth is useful.

Predators do not refuse frogs either. Larger freshwater sharks swallow ducklings and waders, devour water rats, and squirrels crossing the river.

Once, wrote the famous Russian zoologist of the 19th century Leonid Sabaneev, a pike grabbed a large and strong goose by the leg and did not open its mouth even when it pulled it ashore.

Pikes can swallow even such fish, the length and weight of which is about half of their own. The victim is always captured from the head. It is held by those teeth of the lower jaw, which have different sizes. Other, smaller teeth are pointed towards the pharynx and may sink into the mucous membrane of the mouth. If the fish tries to escape, they rise from the mucous membrane and dig in like a thousand needles.

The pike feeds in the morning and evening, and almost always sleeps at noon and at night. She eats until, in the words of L. Sabaneev, she is full of fish up to her throat. A hungry predator loses all caution and rushes at everything living and even inanimate - if only it shines. Robbers assimilate only the soft parts of the body of fish, belch bones and scales.

BY MAGIC

With the onset of cold weather, the pike leaves for the nearest pools, where it rests and almost does not eat. There she hibernates.

Immediately after the ice melts off the banks of rivers and lakes, a hungry pike begins a spring fever. At this time, in shallow water, she spawns. There is quite enough oxygen, which favorably affects the development of eggs.

During spawning, pike, having started mating games, splash noisily. Near one toothy beauty, from two to four gentlemen curl up, and larger matrons gather up to eight suitors.

The future mother rubs against pieces, stumps and other objects. At this time, caviar is spawned. Several males follow her at once, obeying the pike's command, they fertilize a significant part of the litter.

One fish, depending on its size, gives out “on the mountain” from 17 to 215 thousand large eggs, which quickly stick to the vegetation. Beads stuck to the legs and feathers of birds can be carried over long distances.

After a couple of days, the eggs, having lost their stickiness, crumble and lie at the bottom. Their development ranges from eight days to a crescent. Having finished with the contents of the yolk sac, the larvae switch to "pasture" food: they eat cyclops and daphnia, and soon they swipe at the larger inhabitants of reservoirs. During this time, they grow and develop rapidly. Males become sexually mature in the fourth, less often - in the third year of life, females - in the fifth.

RIVER SANITARY

How many years does a pike live? L. Sabaneev in his book "Life and Catching Freshwater Fish" gives such a curious example.

The German emperor Frederick II Barbarossa allegedly personally caught a pike in 1230 and, putting a ring on it, released it into Lake Beckingen near the Rhine. The ringed pike was caught 267 years later. Its length was about six meters, and it weighed almost one and a half centners. From old age, the mighty fish has completely turned white. The portrait of the long-liver is still preserved in the castle of Lautern, and the skeleton and the ring are in the cathedral in Mannheim.

One German naturalist became interested in the legendary pike. He reasoned that no living creature is capable of living for two and a half centuries. And, of course, I revealed a lot of exaggerations.

The most compelling argument debunking the version of the Beckingen long-liver is that the common pike, according to leading ichthyologists, lives for a little more than 20 years. True, there is information about the capture of a 33-year-old pike, but this is an exception. Therefore, beautiful stories about long-lived pikes are just fairy tales.

The freshwater shark is a natural regulator of the fish population. Throughout its life, the pike eats insignificant trifles, destroys the sick and the weak, allowing the rest of the scaly tribe to grow faster. For example, in the oxbows of Poronai and Tymi, where there is a pike, the crucian carp is always large, kilogram. And where it does not exist, it is small and degenerates. The destruction of a river orderly in a reservoir threatens to disrupt the biological balance.

BY THE WAY

In Russia, pike was referred to as "black", that is, third-rate fish, since it requires either complex culinary processing or techniques aimed at softening meat in order to drown out a specific smell. In addition, it is skinny, contains no more than three percent fat. In general, pike meat is not for everybody. Nevertheless, the fresh pike cutlets that I was once treated to are simply delicious.