Migration behavior of fish. Fish migrations What is migration in fish briefly

Migrations of cod The ground-dwelling fish cod is of great commercial importance. Its fishery is well developed in the seas of the European north. Soviet and foreign researchers have been studying the biology of this fish for decades. The migrations of Norwegian cod have been studied in detail, namely

Flounder migrations Do migrations exist in fish that are tied to the bottom and are poorly adapted to long-distance movements due to the shape of their bodies? Do flounders migrate? After all, it is difficult for them to swim for a long time, because their body cannot be positioned vertically when swimming?

Migrations of lake fish Freshwater fish, which spend their entire lives in lakes and rivers, also make migrations, both vertical and horizontal, but the latter are shorter than those of marine fish. Some lake fish temporarily leave the lake and go to quite

Migrations river eel I would like to especially dwell on the amazing migrations of the river eel. There is so much mystery, sometimes difficult to explain, in the behavior of this valuable commercial fish! The eel lives in the rivers of the European coast Atlantic Ocean where it is important

Migrations of sturgeons The most ancient of our migratory fishes are sturgeons, which are found in the Black Sea, Azov, Caspian, Aral and Baltic Sea basins, in Baikal and in some reservoirs Far East. The closest ancestors of modern sturgeons

Migrations of sea salmon Even more striking are the migrations of sea salmon going from the sea to the rivers to breed. This refers to Atlantic salmon (salmon and taimen) and Pacific salmon (chum salmon, pink salmon and others), which are also called Far Eastern salmon. Atlantic salmon

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Memory B Cell Migration Model: Applications to Housekeeping Genes Can somatic cells invade reproductive organs and thus come into close physical contact with germ cells? According to Harry Rothenflu, the role of such a “connector”

8.1. The nature of biogenic migration of atoms in the biosphere According to V.I. Vernadsky, the work of living matter in the biosphere can manifest itself in two main forms:? chemical (biochemical) – type I geological activity;? mechanical - the second type of such activity. Geological

The migrations of fish, that is, their journeys from one place to another, like the flights of birds, represent a phenomenon of the deepest biological meaning and majestic beauty. Fish migrations are also of great commercial and economic importance, since the main catch of fish is carried out along the routes of their mass movements, both in the sea and in lakes and rivers. The most ambitious in scale are the migrations of marine fish and migratory fish, which migrate to fresh waters at certain periods of their lives. But purely freshwater fish migrate for the same reasons as sea fish.

Fish migrate in search of food. The cod, emaciated during spawning off the coast of Norway, goes east to Murmansk waters, where it finds good pastures. This is feeding migration. Salmon from the sea goes to rivers to reproduce - spawning migration. Some fish leave their summer places for the winter to deeper places - wintering migration.

Fish also have vertical migrations, when they move in whole herds from one depth to another, from the bottom to the surface and vice versa. These trips are often in the nature of feeding migrations. Zooplankton (the smallest animal organisms that serve as food for fish) are concentrated in the upper layers of water at night, and deeper during the day. Following the plankton, the fish that feed on them move.

Fish migrations are also associated with temperature, light conditions, water flow, and wind direction. In many fish, eggs and larvae are carried by currents over long distances.

In 1911-1912, I traced in detail the migration of the Caspian lamprey. Until that time, such observations of this extremely secretive fish had not been made.

Migrations are clearly expressed in Atlantic, Pacific (Far Eastern), Caspian and Black Sea herring.
Atlantic, so-called Norwegian, herring approaches the shores of Norway in the spring, heading for spawning (spawning migration), after which it migrates to the Barents Sea pastures (feeding migration).

The bottom fish cod is of great commercial importance. Its fishery is well developed in the seas of the European north.

Freshwater fish, which spend their entire lives in lakes and rivers, also make migrations, both vertical and horizontal, but the latter are shorter than those of marine fish.

I would like to especially dwell on the amazing migrations of the river eel. There is so much mystery, sometimes difficult to explain, in the behavior of this valuable commercial fish!
The eel lives in the rivers of the European Atlantic coast, where it is an important fishery object.

About freshwater fishMigrations of the Caspian lamprey

Migrations are the regular movements of fish along certain paths at certain times of the year. These regular wanderings are one of the most interesting phenomena in the life of fish and are extremely important for their fishing.

Individuals, small groups of fish and large herds or schools can migrate. Rare fish lead a sedentary lifestyle, living all the time in a certain small area. Most fish undertake more or less extended movements, sometimes gathering for this purpose in very large schools or shoals. These schools are fished by fishermen in certain areas in which the fish come or through which they pass. The migration routes of fish do not always remain named. Sometimes due to change external conditions The migration routes of fish also change. Migrations can be divided into passive and active.

Passive migrations are the transfer of fish larvae or eggs by currents. An example of passive migration is the removal of hatched larvae of Murmansk herring by jets of the North Cape Current of the Gulf Stream from spawning grounds off the northwestern coast of Norway into the Barents Sea.

Adult fish migrate actively. Active migrations include feeding, spawning and wintering.

Migrations are divided into anadromous and cathodromic. Anadromous migrations are movements in which fish move up the river or from the sea to the shores. Cathodromic migrations are the movement of fish down a river or from the shores into the open sea.

Let us give examples characterizing certain types of migrations.

Feeding migrations. There are many examples of active migrations for the purpose of Nutrition. Black Sea mullet, sea fish in at a young age to feed on plant remains (detritus) in the spring they enter shallow brackish water coastal lakes- estuaries. They pass into them through narrow, sometimes specially dug channels. With the onset of cold weather, the mullet, which has fattened and reached commercial size, goes back to the sea. Or, for example, cod migration Barents Sea. This cod, after breeding off the coast of Norway near the Lofoten Islands, emaciated, skinny, hungry, moves, feeding, into the Barents Sea. Cod in the Barents Sea feeds mainly on fish: herring, capelin and, to a lesser extent, crustaceans. A number of other marine fish can be mentioned that undertake extensive migrations for feeding purposes. Particularly significant are the movements of tuna, swordfish and some sharks, moving from one ocean to another in search of food.

Spawning migrations. The spawning migrations of migratory fish are especially interesting and most studied. A typical example is the migration of Atlantic salmon. Atlantic salmon for breeding from northern seas where it lives, it enters rivers and, as a rule, rises high along them. Thus, its spawning migrations are an example of anadromous migrations. Atlantic salmon spawn in the fall. They enter rivers at different times of the year, at different ages and various sizes. The desire for breeding grounds is very strong in salmon. On its way up the river, it overcomes small rapids and even waterfalls, sometimes making huge jumps up to 4 m above the water. Salmon spawning occurs in shallow places in the upper reaches of the river with a flat sandy pebble bottom, with transparent and cold water. Another example of spawning anadromous migrations of migratory fishes is the migration sturgeon fish(thorn, sturgeon, stellate sturgeon and beluga). Sturgeon begin their spawning migration in the spring. The height of their ascent along the river depends on the availability of places with a pebble bottom that are convenient for spawning.

Much less often among migratory fish, examples of cathodromic migrations are observed, when rivers are a feeding place for fish, and the sea is a breeding place. This type of migration is found in European river eels. Upon reaching sexual maturity, the European eel begins to leave the rivers where it fed and grew into the sea. In the sea, the eel moves from the shores of Europe to the shores of Central America, where its breeding grounds are located above great depths. Sea fish They also make spawning migrations. Atlantic cod, for example, after finishing their feeding period, makes a spawning migration from the eastern part of the Barents Sea to the Lofoten Islands. Sea flounder usually moves away from the shore to considerable depths to spawn.

Freshwater fish also move higher up rivers or move from lakes to rivers to reproduce. These are sterlet, Volkhov whitefish, burbot, asp. However, usually the spawning migration routes of freshwater fish are shorter than those of anadromous or sea fish.

Wintering migrations. Wintering migrations of fish living in the Northern Caspian Sea are typical. Carp, bream, and pike perch gather in large schools in the fall and migrate to the banks and river deltas, mainly to the Volga. Here these fish lie in special pits for the winter. The wintering migrations of the Azov anchovy in the fall from Sea of ​​Azov through Kerch Strait to the Black Sea. Hamsa is a typically pelagic planktivorous fish. After fattening in the Sea of ​​Azov, it gathers in large flocks in the fall and exits through the Kerch Strait into the Black Sea. Then it moves to the southern shores of the Caucasus, descends in winter from the surface to depth, where it spends the winter. In the spring, having risen to the surface, anchovy migrates back to the Sea of ​​Azov for spawning and feeding.

The above types of migrations cannot be considered in isolation. The migrations of each fish are connected with one another, transforming one into another. All types of migrations in fish represent separate stages of the general annual migration cycle.

Methods for studying migrations. The simplest way to study migrations is to analyze changes in commercial fish catches in individual fishing areas. By comparing increases and decreases in catches in individual fishing areas, one can get an idea of ​​the movements of fish.

The best method for studying fish migrations is tagging them. To obtain successful tagging results a necessary condition is to carry out tagging on a mass scale and in those areas where fishing is sufficiently developed, since the main task is the return of tags or re-caught tagged fish. The tags used for individual tagging of fish are varied. The main requirements for them are that they do little damage to the fish, are light, and clearly visible. Currently, the most common are various hanging tags made of polyethylene tubes and films of the “ampoule” and “envelope” type, attached with a thin wire or nylon thread to the base dorsal fin fish.

They move long distances in the World Ocean, often finding themselves on the verge of exhaustion. What makes them do this? long haul, and what is their reference point?

The Mystery of the Atlantic Ocean.

It is difficult to find any other fish whose life has been so little observed as that of the river eel. It is not for nothing that fantastic legends have been made about this fish. Some, for example, claimed that eels come from earthworms, others believed that they are born from the viviparous eelpout fish, others said that eels reproduce differently from other fish, that they do not have caviar. It turned out that eels go to sea to spawn. The reproduction of these fish has been shrouded in mystery for a long time. In the spring, small transparent fish suddenly appeared at the mouths of European rivers, which after a few years turned into adult eels.
Adults went to sea irrevocably. Participates in migrations large number acne: it is estimated that only in Southern Europe 25 million eels leave freshwater bodies annually. Eels go to spawn like salmon, only in opposite direction. As is known, salmon living in different seas and oceans, breed only in the mouths of freshwater rivers. And eels, therefore, travel from freshwater bodies of water to the sea.
After many years Research has determined the place where eels go to spawn - this is the Sargasso Sea, located in the central part of the Atlantic Ocean. Eels breed only in this place, located 6000 km from the European coast - in warm water(20 ° C), at a depth of 300 m. After spawning, the fish, exhausted by the six-month journey, die. Eel larvae, along with the currents of the Gulf Stream and the North Atlantic Current, slowly drift to the shores of Europe, which they reach only next year. By this time, the fry, the so-called glass eels, reach about 7.5 cm in length. They enter river mouths and swim to the sources. Adult eels migrate in the Sargasso Sea using a biological sense of timing and direction. The sense of orientation in fish is better developed than in birds, controlled magnetic field Earth.

Movement monitoring

Fish migrations continue to remain mysterious phenomenon. Each species usually consists of several distinct populations occupying specific habitats, and spawn in different times. Modern researchers have a large range of devices and devices that allow them to track the movements of fish. They use various types transmitters: UHF, microwave and acoustic. The type of transmitter used in each case depends on the location and fish species. A typical telemetry device is an acoustic signal transmitter, placed in the stomach or in a recess on the body of the fish, from where it sends ultrasonic signals. sound signals, which, with the help of special equipment, are converted into ordinary sound signals that the human ear can pick up. These signals can be recorded at a distance of up to 1 km from a ship or from shore. Thanks to such devices, researchers today are well aware of the migration routes of fish.
Previously, biologists could only conduct observations directly at sea on board a research vessel. Modern equipment makes their work easier, without requiring the constant presence of a person near the habitats of certain species of fish. In search of food sources, fish travel considerable distances, but they always return to certain places for spawning To breed fish, they choose the conditions that are optimal for the development of their fry.

Why do fish migrate?

Fish migrate in search of food and breeding sites. Many species follow the source of food, changing their place of residence according to the time of year - they live where, for example, there are large accumulations of plankton, consisting of microscopic plants and animals that are found in the water column. There are species that breed far from their places of existence - they migrate to spawning sites. One of the reasons for this behavior is the difference in the needs of adults and fry. Thanks to migrations, the fry are not in danger of being eaten by adult representatives of their own species.

Once in a lifetime

Salmon are born in fresh water and breed in shallow river waters, but they spend almost half of their lives in the sea in search of food. Salmon feed on herring, mackerel and other fish. Most salmon spawn only once in their lives and die after spawning. Salmon spend about 4 years at sea. They live in the plankton-rich waters of the Atlantic Ocean off the coast of Greenland, where they feed under the ice. Having reached sexual maturity, salmon travel many thousands of kilometers to rivers to spawn. Salmon stop at river mouths, waiting for the tide to carry them into the river channel. The months-long journey of salmon begins at river mouths. To reach the final goal of their journey, fish overcome current resistance, rapids and waterfalls. During these migrations, salmon do not take food, therefore, after the completion of spawning, most fish, losing up to 40% of their body weight, die. For example, after the first spawning, all adult Pacific salmon die.
In the upper reaches of rivers.
Most fish migrate within the sea, but there are species that migrate from the sea to rivers. For example, brook trout, or brown trout, go to sea in search of food in the spring. It, unlike most other freshwater fish, can live in salt water. In the sea, brook trout fatten up quite a significant mass - the fish become almost twice as large and heavier than their river relatives. Only at the end of summer do trout streams return to the upper reaches of the rivers to spawn.
This is explained by the fact that the eggs and juveniles of brook trout can only develop in fresh water.
Marine navigation
Salmon navigate in water using their sense of smell. Every fish remembers well the smell of the river in which it was born. The fish returns to spawn in their native river, guided by smell. She follows the very traces and eventually ends up in her “cradle”. Salmon confidently find spawning grounds, unless their habitat has been destroyed or there are obstacles on their route: dams or artificial reservoirs. The fry spend about a year in the river, then they move downstream to the sea. Features of marine navigation.
Migrations from rivers to sea- not an easy matter. Sea water contains more salts than fresh water, so fish need to learn to regulate the salt content in the body when moving from one environment to another. IN fresh water ah, the fish’s body contains more salts than the environment, so water passes through the skin into the body. This phenomenon is called osmoregulation. Excess salts to avoid excessive concentration from the body freshwater fish excreted in urine. Sea water has a high salt content, so osmoregulation proceeds in the opposite direction: fluid is removed from the body to the outside, and the fish is at risk of dehydration. As a result, the fish drinks sea ​​water, causing her urine to become less concentrated. Marine fish, depending on their habitat, are divided into pelagic (living in the water column) and deep-sea fish. Pelagic fish have swim bladders to provide buoyancy. Every fish that migrates from rivers to the sea experiences changes in conditions. aquatic environment. Excess fluid is gradually removed from the fish's body, then the fish restores its loss. Fish for which habitat changes are not associated with particular difficulties include brook trout and salmon. By the way, I recently came across a good resource on the Internet, the world of advice. I found a lot of interesting things there, for example, how to tie a tie correctly,

Chapter IX

MIGRATIONS

Migrations are a phenomenon of majestic beauty and deep biological meaning in the life of fish. At the same time, they are of paramount importance for fishing: mass fishing of many fish is carried out along the routes of movement of their herds. Therefore, much attention is paid to the study of fish migrations and an innumerable number of notes, articles, and books are devoted to this problem. One of best books is the already mentioned monograph by P. Yu. Schmidt - “Migrations of Fish” (1947). The book is enriched with information about fish migrations gleaned from Soviet and foreign literature. Those starting to study fish migrations should thoroughly study P. Yu. Schmidt’s book before starting their research. A summary of fish migrations by the English researcher Meek (1916) is also known. Fish migrations are described in detail in the books of E.K. Suvorov (1948), G.V. Nikolsky (1963) and other manuals on ichthyology.

Classification of migrations and their biological significance

Mass movements of fish are caused by the needs of their body for different periods life cycle and seasons. They are mainly associated with reproduction, feeding and wintering.

The movements of fish to breeding grounds are called spawning migrations. Salmon from seas or lakes go to breed in rivers, sometimes over vast distances. Atlantic eel, on the contrary, are sent from fresh waters to spawning grounds located in the ocean, thousands of kilometers from their feeding grounds.

Fish moving in search of food make feeding migrations. For example, cod, emaciated after spawning off the coast of Norway, heads east to Murmansk waters, where it finds good pastures.

Many fish go to deeper parts of the reservoir for the winter; such migrations are called wintering. They are characteristic of some fish of the Northern Caspian Sea, which occur in masses in pits. After feeding in the Sea of ​​Azov, the anchovy goes to the Black Sea for the winter.

To monitor the survival of tagged fry, a certain number of fry are left from each batch and kept for some time. This is possible mainly by marking fry artificially bred in fish hatcheries.

To ensure a sufficient return, it is necessary to mark a significant number of juveniles at the same time, i.e., several tens of thousands, keeping in mind their large natural mortality. All persons involved in the fishery should also be widely informed, as these marks are less noticeable and can be more easily missed during a secondary capture, especially by an uninformed person.

Processing flow results

When processing tagging results, you should use a special card filled out for each second specimen caught. This card contains all the information related to this specimen at the time of tagging and, at the same time, at the time of the secondary capture (the first is written out from the tagging log, and the second from the card filled out when submitting the tag).

Below is an example of such a card. This card can be supplemented with additional items about the time elapsed between tagging and secondary capture, distance traveled, average daily migration speed, direction of migration, or other information depending on the purposes of the study. The use of such cards greatly facilitates and speeds up the work.

When studying migrations based on tagging results, information about secondary captures is plotted on the map for greater clarity. Usually, the place of release of tagged fish is marked on it with a bold circle or square, and the points where tagged specimens are caught are marked with small circles or dots. Or the result of tagging is depicted as a bunch of lines or arrows extending from the tagging point and ending where the tagged fish were caught. These lines represent the expected or expected migration path of one or a group of fish.

If with such an image you need to somehow highlight separate groups secondary captures or divide the material for comparison according to certain characteristics (for example, separate males from females, divide by maturity, by length, by fishing seasons, by the method of secondary capture, by belonging to a particular country of the vessels that delivered the tags, etc. ), then secondary capture points are respectively indicated by different icons or, more clearly, by different colors.

Sample card

Now they are beginning to use the method of radioactive tracers, called the method of labeled atoms. But to use this method, serious specialized knowledge about radioactive substances (radioactive isotopes), full familiarity with the methods of using these substances. Requires appropriate equipment and exceptional precautions on the part of the practitioner. radioactive substances. Methods for tagging fish with radioactive substances were outlined by A. S. Troshin (1956).