To understand how to preserve a body of water and the fish stock within it, we must dive into the vast ocean of knowledge — knowledge in the fields of ichthyology and fish farming. This knowledge is essential for anyone who wants to take a competent part in increasing the yield of fish from the country's inland waters. And we will begin our voyage across this ocean of knowledge with a look at our planet, Earth.

– But what does the planet have to do with it?

– you may ask.

– Can't we simply talk about bodies of water — rivers, ponds, lakes — and the life within them? Why spend time studying something so broad as the whole planet, when what interests us is a specific matter: fishing and its success in small freshwater bodies?

Our beautiful planet

So, let us start with our beautiful planet. A great deal of time is needed to travel across even part of it. Given such enormous distances and the time required to cross them, our planet would seem to be very large. But then the first cosmonaut, Yuri Gagarin, rose above the planet and circled the globe in just an hour and a half.

He saw that our beautiful planet is not so vast after all. Later, weather satellites began circling in space, revealing the global, all-encompassing nature of the planet's atmospheric processes. Jet airliners now carry passengers 10,000 kilometres in a matter of hours — a distance that Semyon Dezhnev and his Cossacks once took several years to cover; read more: How people travelled in the past.

Radio, television and newspapers carried information from every corner of the planet. And suddenly we learn that the destruction of forests and vegetation across Vietnam, where the Americans used special poisons — defoliants — led to climate change and the drying-up of water bodies in neighbouring countries.

And was not the clearing of the wild, impassable rainforest in the valley of the Amazon the cause of the unusually cold winters in North America in recent years? No, our planet is not so vast after all. Enormous excavators gouge deep canyons out of level ground, factories belch acrid smoke and unburnt particles through their chimneys, a mountain blocks aircraft from landing on a new airfield — so it is "sliced away"...

Humanity now holds mighty technology in its hands. But in wielding it, people are far from always aware that actions taken in one place on the planet will produce quite unexpected and by no means favourable effects in another. The widespread use of insecticides on the fields of the USA against crop pests led to the destruction of fish in many of the country's rivers and lakes.

And do you know where the smoke from American factory chimneys settles? In England and Norway! Poisoning with chemical waste the rivers, lakes and fish-rich coastal sea waters there. On the one hand, how can one not marvel at the gigantic development of modern technology, at the astonishing, until recently seemingly fantastical and unattainable victories of that technology over nature. But on the other hand...

A hundred years ago, F. Engels wrote in his book "Dialectics of Nature":

Let us not, however, flatter ourselves overmuch on account of our human victories over nature. For each such victory nature takes its revenge on us. Each victory, it is true, in the first place brings about the results we expected, but in the second and third places it has quite different, unforeseen effects which only too often cancel out the first.

It was in those years that advanced biologists first conceived the idea that sciences such as botany and zoology were not enough to study life on our planet, that some new, comprehensive science was needed — one that would study life in connection with its environment, and all the representatives of life — all species of plants and animals — in their interrelationships with one another.

Ecology

This new comprehensive science, which investigates the various aspects of relationships within the systems "organism–environment", "species–other species", "animals–plants", "living–non-living", was named ecology (from the Greek words "oikos" — dwelling, and "logos" — science).

In the modern understanding, ecology is the science that studies the conditions of existence of living organisms and the relationship between organisms and the environment in which they live.

Alongside this definition there is another, given by the well-known American scientist E. Odum, who studied the ecosystem: ecology is the science of the structure and functions of nature.

Knowledge of the structure and functions of nature

This means that to be useful to nature, to increase the benefit nature provides to people, we need knowledge of the structure and functions of nature.

Man lives by nature — this means that nature is his body, with which he must remain in constant communion so as not to die. That man's physical and spiritual life is inseparably linked with nature means nothing other than that nature is inseparably linked with itself, for man is a part of nature.

– wrote K. Marx. Man is a part of nature, but a special part: he is the only living being on the planet that creates tools of labour, and in the course of labour his reason developed. In the beginning, the peoples who arose on the planet did not introduce significant changes into the structure and functions of nature. The Slavs practised farming, fishing and hunting.

For the most part they lived in rural areas and provided for their own food. In the jungles of the planet's tropical regions, tribes hunted, engaged in nomadic cattle-herding, and to a lesser extent in farming.

Of course, burning down the jungle to clear a plot for farming is an ecological catastrophe, a restructuring of the entire structure and functions of nature on that patch of land. But how many such plots existed on the planet, and how many people were there in general? Their numbers did not exceed the threshold beyond which they ceased to be a part of nature.

The era of industrial development

Things turned out differently in the era of industrial development. The planet began to be covered with cities, factories and mills appeared, and the area of agricultural land increased — to feed the cities, more produce was needed. And people were least of all concerned with questions of their relationship with nature; in the pursuit of profit they mercilessly encroached upon it, crowded it out, mutilated it.

The pressure on nature intensified still further in our own century, in the era of the scientific and technological revolution, when science, engineering and technology made humanity all-powerful. And the pressure of a technologically armed modern society on nature proved so significant that new terms had to be introduced to describe the disruption of the structure and functions of the biosphere.

Thus, the pressure of humanity on nature came to be called anthropogenic pressure, that is, pressure generated by anthropos — the human being.

Natural disasters, the unforeseen consequences of technological intrusion into nature — those second- and third-order effects that nullify useful intentions and results — began to follow one after another in different countries, and then their scale grew so large that people started writing about an ecological crisis, about a danger to nature on a planetary scale.

A society of private enterprise is a chaotic society, with its own culture of consumption. Giant cities grow, endless fields spread, science, engineering and technology develop rapidly. Yet people began to try to comprehend nature,

to correctly understand its laws and to grasp both the nearer and the more remote consequences of our active interference with its natural course

(F. Engels, Dialectics of Nature). Human society cannot exist without exploiting nature in order to produce material goods. But this must be done wisely, so as both to satisfy the needs of society and to preserve the structure and functions of nature.

Catching fish

Take, for instance, such an example as catching fish from some body of water. It might seem that the more we catch, the better for people. But that follows the principle: take, take, and after us the deluge! Yet it is impossible to catch as much as the fishing gear and modern technology allow. Why?

Because we must think both of ourselves and of our descendants. Fish must be caught not only today; there must be enough for us, for our grandchildren, and for our great-grandchildren. How is this to be achieved? Evidently, by learning certain laws of nature.

If we are dealing with a particular lake, we must study well the laws governing the development of that water body as a closed ecological system. When we have studied the number of species of living nature, the characteristics of the non-living environment, the interrelationships between animals and plants and between the various fish species themselves, the feeding relationships, energy flows and many others existing in this environment, only then can we derive the permissible degree of exploitation of this natural complex.

The fish stock in a body of water

The fish stock in a body of water must be large enough that the fish population in the lake can make up the losses caused by fishing through the growth of new generations. This means that fishing gear — nets, for example — must be built (in a net this means the size of the mesh) so as to retain large, so-called commercial, fish while freely letting the small ones, the young, pass through.

The stock depends on the productivity of the fish population, and productivity is determined by five characteristics:

1. birth rate,
2. survival,
3. growth rate,
4. dispersal,
5. utility coefficient.

• Birth rate depends on the fecundity and viability of the roe (the proportion of eggs that develop into fry).
• Survival shows how many fish — usually calculated as a percentage — develop to commercial weight.
• Dispersal is determined by the habitability of the water body (it sometimes happens that not the whole water body suits the fish but only part of it — its size and food supply must be determined, and one might even take measures to enlarge that part).
• Utility coefficient is the ratio of the useful and useless parts, for humans, in the organism.

With fish, scientists do not yet carry out the kind of experiments they do with plants: reducing the height of the ear while increasing its grain weight in wheat, cutting back the tops of potato plants so the plant's energy is not wasted on useless greenery but goes into the tubers, and so on. Suppose we have managed to calculate all this. But what is needed is not just fish, but fish of a particular species — say, pike-perch. And pike-perch is a predator.

This means its productivity also depends on the productivity of certain fish it feeds on. Now we must calculate the productivity formula for the pike-perch's food... The field farmers want to use the lake's water to irrigate their fields — set about calculating how much water can be taken from the lake without harm to the fishery...

On the lakeshore there is a jetty for the motorboats of water-travel enthusiasts. And how many boats can be allowed onto the lake without affecting its yield?.. How will runoff from a duck farm affect the water, its chemical composition, the productivity of the tiniest animals — food for the fry? And a pig farm on the other shore — can its runoff be allowed into the lake's water?...

The size of the catch

It seems so simple: let the fish be big and only big, let there be plenty of them. It turns out that determining the size of the catch is a most complex science. And a responsibility. The responsibility of those who make the calculations, for the slightest error irreparably distorts the structure and functions of nature and causes irreplaceable damage.

And this is on the scale of a single lake, a closed body of water. There you have ecology. For the competent, careful and responsible exploitation of a lake's riches requires taking account of all its ecological interrelationships.

The ecosphere

Now imagine another, likewise closed, system — only no longer on the scale of a lake, but on the scale of our entire planet Earth — the biosphere, or, as some scientists call it, the ecosphere.

How much knowledge, how much caution, what responsibility people need in order to use this wealth of the planet — to use it not only without depleting or destroying it, but also to multiply it and to promote its fuller development! And this concerns all the people of the planet and all of humanity, and each individual person separately.

The fish of our waters make up a comparatively small part of the whole of our country's nature, yet the protection of nature not only helps to preserve a body of water and its fish stocks but also contributes to conserving and increasing the natural wealth of the whole world. Consequently, any step, any useful action that protects nature takes on a planetary character and scale — that is, worldwide significance.

Therefore, the more effective human actions are in caring for natural riches, the more beautiful the nature of our beautiful planet will be, and the greater the hope for all humanity that our planet will remain living, blue and green — not only for us who live now, but also for those who will live upon it after us.