No. 47 - 1984 e u ro p e a n GMampa

information Editorial Paddy O’Toole 3 c e n tre A very special environment Ignacio ClaverFarias 4 for (Photo G. Kraczkowski) n a tu re Portrait Of a fish Wilhelm Harder 6

conservation Multiple threats Niis-ArvidNilsson 9

The Thames is alive Derek Gren 12

chubert’s “Trout” must be one of These contradictory views of the benefits fish alive. The bacteria which recycle New life for the Rhine Helga inden 13 the most widely known and loved of water make it difficult for us to com­ our waste products, turning them back S themes in European music. The prehend its value. Those who actively again to water, carbon diôxide and Biotopes Anton Lelek 14 trout—fish and music—conjures up work to preserve it are relatively few simple chemicals, also require oxygen. thoughts of brilliance, purity and free­ and are regarded by many as belonging Here there is two-way traffic: water ★ as dom: the sparkle of a mountain stream to the lunatic fringe of conservationists. with the help of its oxygen purifies the All is not lost HenriHoestlandt 20 and the wildness of a leaping fish. Somewhere there must be a point of sewage but the sewage uses up the balance between the extremists on the oxygen. If there is too much waste, all one hand who say "Our waters are too the oxygen is used and the waste can Pollution Enrico Getosi 22 precious to allow anyone to interfere no longer be made safe. In that event Symbol for the Council of Europe 's nature with them" and those on the other the water becomes unfit tor use by man, conservation activities. who argue “Our business brings so much beast or industry. Long before this oc­ Life - giving rain? wi/iiam Dickson 25 employment that we are entitled to do curs, the fish die and the fishermen what we wish with the water”. complain. Their complaints must be given the most urgent consideration LakeOf Geneva Bernard Buttiker 26 The earliest Europeans had an especially because the death of fish is the pre­ Naturopais published in English, French, close affinity with water. They were cursor of the death of the water itself. German and Italian by the European hunter-gatherers who had learned the Information Centre for Nature Conserva­ Stocking and re-stocking m. p. Grimm 27 skills of the fisherman. Fish such as Today, after centuries of study of water tion of the Council of Europe, BP 431 R6, the salmon, easily caught in winter when and of every creature that lives in it, F-67006 Strasbourg Cedex. other food was scarce, sustained our our scientists can tell us what we need Editor responsible: Hayo H. Hoekstra Man-made lakes Jan Kleinert 29 forefathers. Modern Europeans can live in the form of water quality. What is Conception and editing: without fish but do not want to. The more, they know not only how to main­ Annick Pachod numbers who fish for a living have tain our water supplies in their ideal Gérard Lacoumette declined as easier ways of raising an state but how to restore watercourses Adviser for this issue: which have been spoiled by indifference Dr. A. Lelek, income have increased; in their place Forschungsinstitut Senckenberg are millions of recreational fisherfolk in the past. who follow their sport with fervour. (Federal Republic of Germany) But knowing what to do is not enough. Printed by: Georges Thone, Concern over the quality of water has The public must be prepared to pay the Liège (Belgium) in a great many cases been spear­ cost of maintaining water supplies in a Repros: Gam Grafic, headed by the sport fishing community. clean and unpolluted state. The demands Herstai (Belgium) It is obvious that fish need water, but for immediate cheap energy, food and Articles may be freely reprinted but it the chemical and physical nature of consumer goods conflict with the long­ would be appreciated if reference is the water is of equal importance to their term needs of maintenance of clean made to the source and a copy sent to the well-being. Fishery scientists have shown water supply. The costs of dealing with Centre. The copyright of all photographs Fishes how the trout needs water of the highest the causes of acid rain and other forms is reserved. quality if it is to survive at all. The of water contamination will undoubtedly The opinions expressed in this publica­ be high but our failure to act may prove tion are those of the authors and do not level of dissolved oxygen must be close to its maximum value and the water more costly. necessarily reflect the views of the lthough nearly always hidden from Once many people made a living fishing must be free from excessive quantities of Council of Europe. view, the fish of our lakes and mountain streams for trout, lakes for The future can be bright. In this issue Those of us who have followed rivers silt in suspension. Other fish, such as rivers are none the less important carp and rivers for salmon and sturgeon. o f N a tu rop aone article tells the success A to their sources, or spent peaceful days carp, bream and eels, are tolerant of for that, if only as indicators of the Such fishing has declined consider­ story of the restoration of two of our fishing, boating or swimming know the less oxygen and more dirt but even they healthy condition of the waters where ably, but millions of anglers have taken great rivers, the Rhine and the Thames. value of water—or believe we do. The cannot survive serious pollution. Front cover: Photo G. Kraczkowski they are to be found. Over-fishing, de­ over from the professionals. There have been many less spectacular industrialist whose factory needs many Captions to colour illustrations p. 16-17 struction of biotopes and pollution have If the disappearance of fish from lakes but equally successful undertakings. 1. Dytiscus marginalis tonnes of water every day and the farmer been the immediate causes of the perils As the last of three issues of N aturopa and rivers were the only ill effect of (Photo Anne and Jacques Six) whose crops face disaster in times of Today we rejoice in the certain know­ 2. Natrix maura facing species whose finest specimens on the “Water’s Edge” campaign, this water pollution, it might be possible drought also believe in the miracle of ledge that pollution can be conquered. (Photo Jean-Paul Ferrero/Jacana) once graced the tables of the crowned one is concerned with Europe’s fresh­ to ignore the complaints of fishermen; 3. Pandion haliaëtus water. Yet, we complain when the rain What we need is the will to do it. heads of Europe. water fish. but the welfare of fish is of infinitely (Photo Bengt Lundberg/Natur Fotograferna) falls; too often the industrialist takes greater importance to the community 4. Mustela lutreola Fish have always attracted man, as much This year’s final issue will be devoted the water and renders it unusable for (Photo Bengt Lundberg/Natur Fotograferna) than at first appears. Paddy O’Toole 5. Fly-fishing because of their "secret" life beneath to “Nature and the computer”, a field the rest of the community; farmers beg Minister for Fisheries (Photo J. C. Chantelat) the water’s surface as because of their of growing importance to the Council their governments to drain away surplus The oxygen in water does much more and Forestry sought-after flesh. of Europe. H.H.H. water. for the benefit of humanity than keep Ireland at La Granja de San lldefonso (Segovia). The same year saw the first work of the piscicultural establishment of the Monasterio de Piedra de Alhama de Aragön (Saragosse). The Spanish revolution in 1868 put a stop to work on fish farming, which was not resumed until 14 years later. By about 1950 there were 12 state fish farms in Spain. Today we have some 200, both state- and privately-owned. (Drawing NCC) Its natural conditions make Spain ideal for fish farming, especially the tem­ perature of the water which may be either cool or warm. Cold water has been used only for A very special environment breeding salmonids, especially rainbow trout. It still has great potential for breeding other types of fish. However, Inland ichthyological fauna much of our water is within the tem­ perate range. This, in theory, is the best, In Spain, the river network is 72,000 km Ignacio Claver Farias because it favours more rapid growth. long and the surface area of still water One of the numerous warm water species totally fulfilled by professional sea fish­ is more than 250,000 hectares. Twenty is the eel, for which there is a market ing, and inland fishing survives only in families and fifty-nine different species of many millions of kilogrammes in certain areas. At the same time, there of fish live in them. From this informa­ pain’s deeply rooted and tradi­ central Europe and, aside from the very has been a rapid increase in fishing tion alone, it may be seen that the wild­ tion al involvem ent in fishing is important fact that the natural environ­ for sport, which is very popular in our life is somewhat limited. The number of well known. This is due both to the ment is suitable, we are also able to S country, given that one in every 45 Spani­ fishing species in our inland waters is, great length of its coastline and its obtain large quantities of elvers as ards is an angler. in fact, less than that of other European many rivers, as well as to the consider­ countries, mainly for climatic and geo­ seedstock. able surface area covered by still, natural However, a whole range of factors leads graphical reasons. To close on a note of optimism, Spain water (lagoons, lakes, etc.) and by us to believe that this situation will can look forward to varied and pros­ reservoirs. The existence of other un­ change again. World politics and the However, because we are practically perous development of its fish resources usual expanses of water should not be pressure which is being put on fishing isolated from the rest of Europe by the for conservation, for sport, and for forgotten either; these include the “rias” Pyrenees, we have a highly character­ at the moment have caused a real intensive farming. I.C.F. of Galicia and the Asturias, the Anda- problem. The number of fish caught istic fish population, with fish as hetero­ lucian estuaries, the Valencian Albuféra, throughout the world at present exceeds genous as the Atlantic salmon—king of the Mar Menor in Murcia and the the natural reproductive capacity and, the river—and the flounder Flesus flesus Ebre delta. in addition, the extension of legal a flat asymmetric fish. Moreover, the geographical situation, waters to 200 nautical miles has greatly Zoogeographically, our wildlife is situat­ affected our fishing industry by prevent­ relief and climate of our peninsula have ed between that of central Europe, which ing Spanish vessels from fishing in most always allowed reasonable exploitation is eminently palearctic, and that of of their traditional maritime fishing of various species of fish, some more Africa, which is tropical or ethiopic. sought-after than others. This is why grounds. This is why Spain is quite often the the local population has always been This is why the past 20 years have most northern limit of the geographical very involved in every kind of fishing. seen a renaissance, with even greater distribution of typically ethiopic species energy, of inland fishing, which can or the southern limit of certain typically Where inland fishing is concerned, it provide very good, cheap food by the palearctic species; moreover, often the should be noted that our legislation introduction and development of modern sub-species of the ethiopic or palearctic considers inland waters as including intensive fish-farming to satisfy con­ species represented in Spain are not all springs, lagoons, lakes, streams, sumer demand. those typical of the species. reservoirs, artificial lakes, canals, albu- féras and rivers, whether their water Fish farms in Spain can be divided into is fresh, brackish or salty, until it two different types, public-service and The development of fish farming enters the sea. commercial. The first, which belong to the State, are basically to provide fish Fish farming in Spain can be traced for sporting and conservation needs. back through the centuries, but it may The most commonly bred fish include: Fishing as a source of employment be said that salmonid farming began Atlantic salmon, river trout, rainbow and livelihood in the 12th century, in the monastery trout, brook trout, pike, carp, large- known today as Santa Maria de Conxo, mouth black bass and tench. Since man’s appearance on Earth, fish­ in the province of Coruna. ing, like hunting, has been one of his The present level of production in The incubation of trout eggs in the indispensable sources of subsistence. commercial fish farms is more than 14th century, although it is not known Today it retains this basic function of 15,000 t with a turnover in excess of whether this included artificial fertilisa­ providing food in the less developed 13 milliards pesetas; more than 5,000 tion, and the discovery of the latter in countries where it always has been, jobs have been created. These commer­ the 18th century, led to the establish­ Fishing, an indispensable source of subsistence and will continue to be, the only avail­ cial farms concentrate mainly on breed­ ment of special fish breeding centres. (Photo J. C. Chantelat) able source of animal protein. ing and marketing rainbow trout and, to a As early as 1866, the first ichthyo- In Spain, as in many other countries, lesser degree, river trout, brook trout, genical laboratory was built in Spain this function of providing food is almost tench and eel. plankton-eaters to consumers of fresh gas exchange takes place. Water js, as epithelium of the gills. This has con­ or dead plant matter and lower forms we have said, a poor respiratory medium;siderable consequences for the fish’s of animal life, whilst some fish species at best, i.e. at 0 °C, it contains 10 ml water and mineral husbandry and in turn prey on others. Jaws have to be of oxygen per litre, barely 1 /20th of the causes high energy expenditure. Fresh­ adapted accordingly. Food is chewed amount available to a land animal. Towater fish, whose blood and tissue fluid small only by carp species, which have obtain the same quantity of oxygen, a contain larger quantities of dissolved gullet teeth next to the rearmost gill fish accordingly requires much more particles, mainly salt ions, than the arch. Jaw teeth, where they occur, serve of its respiratory medium and must be surrounding water, continuously—pas­ only to hold prey fast. much better able to extract the avail­ sively—absorb water via the gills. Their able oxygen from it than air-breathing kidneys accordingly have to excrete animals. Land animals live in conditions large quantities of water in order to The sensory organs of affluence where oxygen is concerned keep their body-fluid concentration and can afford to breathe out 80 % of constant. Since vital ions are lost in The sensory organs resemble those of their oxygen supply unused. That would the process, these have to be replaced. terrestrial animals. However, the eyes be impossible for a fish. A fish is This is done by special cells, ionocytes, have to have a spherical lens in order able to extract at best 60-80 % of the located on the gills. Seafish, on the to develop sufficient refracting power. available oxygen, during fast breathing other hand, have to compensate for The cornea which most land animals only 20 %. Furthermore, water has higher constant water loss via the gills, because use to project an image on the retina density than air and is hence heavier their body fluids contain fewer dissolved cannot work for water animals because and more “sticky” due to its high substances than the surrounding sea­ the refractive index of water and cornea viscosity. This means that it takes a water. To do so they have to drink, i.e. is too similar. As the eyes are located great deal of energy to move it. Con­ absorb a strong salt solution. The ions on the side of the head, binocular sequently, a fish has to use up to which are inevitably absorbed in the pro­ sighting of prey is not possible; all 1 /6th of its energy resources for cess are excreted via the gills. Bony sea objects have first to be perceived paral- breathing. fish have sharply reduced active water lactically against the background before excretion via the kidneys and hence Disposing of the by-product carbon they enter the usually very narrow field the number of kidney corpuscles. Fish dioxide poses less of a problem. It is of binocular vision. able to change environments such as much more readily soluble in water salmon, flounder and eels, have to The sense of smell is located in the than is oxygen and is easily taken up gradually adapt in estuaries. nose, but the nasal cavity is not in­ by the ambient water. The same ap­ volved in the breathing function and is plies to another, more dangerous meta­ These peculiarities of water and mineral separated from the respiratory tract. bolic product, ammonia, which results husbandry show why the gills cannot The sense of taste works through sensors from the breakdown of protein. It too be bigger in order to make better use in the mouth cavity, but which are often is excreted via the gills. The gills are of precious oxygen. Owing to the many also distributed all over the body. The very good exchangers, working on the functions of the gills, water pollution sense of balance so important for countercurrent principle. Water with a affects them particularly, for it is through of buoyancy because of the small dif­ Wilhelm Harder Nor are European waters particularly organisms that move in three planes is high oxygen content flows in the op­ the gills that harmful substances can ference in density between it and organ­ varied in biotopes. Moreover, a large highly developed. Statoliths provide in­ posite direction to the low-oxygen- most easily penetrate the body. Then, isms, but by comparison with air it has proportion of them have been colonised formation about orientation in space.content blood in the gill lamellae. This of course, not only the gills, but the a very high density and viscosity only recently (in geological terms), i.e. Three semicircular canals can detect produces a constant difference in con­ whole body is damaged. (1,000 times more) and offers much since the ice age. This applies especially angular acceleration. Sense of touch centration which guarantees optimum greater resistance to movement. This Space does not permit dealing with the to our mountain regions, where no strik­ and of temperature are also present.exchange. Carbon dioxide and ammonia is particularly important in running water, anatomy of the internal organs here, ing examples of adapted species, such Whether fish can feel pain is a matter are discharged according to the same where current and bodily movement but it is worth mentioning that research as occur in the mountain streams of of controversy, though this of course principle, and so is metabolic heat. may oppose each other. This deter­ has shown only recently that fish have the Ahdes or the Himalayas, are to be does not give a licence to do as one (Very few fish, e.g. some shark and mines the limits within which the fish’s a dual artery system and no lymphatic found. pleases with them. Fish also have a tuna, are “warm-blooded”. By means body must be adapted in terms of shape, system . further sensory system denied to ter­ of countercurrent heat exchangers in anatomy and, not least, physiology. restrial species; it is developmental^ their muscles and liver they are able Life in the water related closely to the sense of hearing, to retain metabolic heat in their bodies.) Its body must be able to overcome the The locomotive system current, which exerts its force especially which they also possess. The sensors A further effect of the gills’ exchange The typical fish’s body is perfectly on the head region. To put it crudely, of the “lateral line system” respond to capacity is that water can also penetrateFishes’ locomotive system is also deter­ adapted to its mode of movement. Fish the current presses against the head the build-up of pressure in the water freely through the necessarily thin mined by their environment. Corre­ are very hydrodynamically shaped, so from the front, the body’s muscular due to the fish’s own movement, the sponding to the fore and hind legs of that energy consumption is kept to a power from the rear. The structure movement of other fish or obstacle f all vertebrates, fish form terrestrial vertebrates are the pectoral minimum. This applies especially to of the skull takes this into account. resistance to current flow. It is not a the group with the largest number and ventral fins. However, the fins are pelagic species, i.e. those which swim But the head is not only a current- sense of flow: a fish can detect a of species: one in two vertebrate rarely used for actual movement, but O virtually non-stop, such as salmon, trout, divider. In abstract terms, it is not change in its position in relation to species is a fish. Of the at least rather for positional stabilisation, for whitefish and most carp. The less active only a “pole of movement”; it is also, the bottom only by eye. The sensors 20,000 species, well over 19,000 are adjusting height and for braking. Most species that keep to the bottom and in order to be able to direct movement, of the lateral line system are located bony fish; some 600 are sharks or rays. free-swimming fish have a swim blad­ swim only intermittently have less a “sensory pole”: it accommodates all in channels around the head and along The remainder is accounted for by der, though it is not used for upward hydrodynamic shapes: flounder, ruffle, the major sensory systems. In addition, the body and can be seen from outside cyclostones: lampreys, hagfish and a or downward movement, because it can­ miller’s thumb, catfish and the like. it is the “nutritional pole”, the point through pores. number of “relicts” such as lungfish, not be quickly expanded or contracted of entry for food and for the oxygen lobefins, gars, mudfish and sturgeon. Water is where life originated—which is at will. It is a hydrostatic organ to that supplies energy. The control of Of these only lampreys and sturgeon not to say that it is a particularly prevent sinking, the fish’s body being movement, direction, feeding, breath­ are found in European waters. All the hospitable environment. It is indispens­ The gills heavier than water. The bladder com­ ing and special, e.g. reproductive, be­ rest are bony fish: some 130 species able for all the biochemical reactions pensates for this difference. It permits haviour necessitates'accommodation of —a tiny number in comparison with that take place in the body, but it The head also accommodates the respir­ rapid diving, in the course of which the main bulk of the central nervous the rest of the world’s fish fauna. is also very constricting. For example, atory organs: the gills. There are usually it is compressed by the water pressure system, the brain, in the head. Europe’s seas account for some 650 it contains only very limited amounts of four gill arches, each with a double row and loses buoyancy. This process then more species; all in all, our fish fauna the oxygen necessary to all higher Where food is concerned, our fish fauna of gill-filaments. These filaments are has to be reversed by “pumping" back are not exactly very varied. forms of life. It affords a high degree is very varied: the spectrum ranges from covered with lamellae through which Design NCC gas from the blood. This expends energy, but probably less than would be needed to provide hydrodynamic buoyancy by constant swimming. On the other hand, it makes rapid upward movement difficult, because the gas expands more quickly as the pressure falls than it can be reabsorbed from the bladder. Fish accordingly avoid rising quickly because of the consider­ tation process in which no oxygen is able strain it places on the organism. necessary. The lactic acid can be con­ verted back again later, using oxygen, In addition to their paired fins, virtually but must not be produced in too large all fish have a number of others, viz quantities, since it would disturb the between one and three dorsal and one whole metabolism, in particular respira­ or two anal fins supported by fin rays tion. which are stiff and pointed, or flexible and branching. Sometimes these un­ White muscle can accordingly only be paired fins form a continuous row. used when there is special need: Colouring Dorsal and anal fins serve mainly for escape, defence, capture of prey. An sideways steering but usually also as extreme example is the pike. In sports display organs with which bony fish terms, the pike is a sprinter. Constant Fishes’ colouring either camouflages show their moods: aggressiveness, fear, swimming at a steady speed requires the fish in its surroundings or serves readiness for mating. The main pro­ “staying power” and relies on a small to give signals, in either territorial or pulsive organ is the tail fin which proportion of “red” muscle. This muscle mating behaviour. The banks of Euro­ helps transmit the mechanical forces is generally found just beneath the skin, pean waters are not exactly colourful developed by the body muscles. The fin as can be seen from any fish fillet. This if compared, for example, with coral Multiple is usually self-cambering to produce muscle is well irrigated, because it needs reefs. Our fish are accordingly also the best hydrodynamic effect.- a constant supply of oxygen and nutri­ rather dull in colouring. Exceptions are ents, mainly fat. It also contains myo­ the wedding dress of the three-spined The locomotive apparatus also includes, stickleback and minnow but they are globin, which helps remove oxygen threats in addition to the motor—the mus­ from haemoglobin in the blood. It is this displayed for only a short period of the. culature—the skeleton, i.e. the vertebra year. Our fish mostly have dark backs red muscle which enables the trout, and the skin. The muscles are attached and silvery flanks. Their back colour­ for example, to withstand the current to both, so that the wave-like contrac­ of a mountain stream or salmon to makeing renders them invisible against the tions of the muscles are converted their way upstream from the sea. To dark background of deep waters. Over into undulating movements of the body. surmount obstacles, they have to rely the lighter-coloured bottom of a stream the colour cells of the skin can con­ Fish muscle is not directly comparable on their white muscle. But even more centrate their pigment in small areas to that of land animals. Its well-known sluggish fish like carp have strong red and so make their overall colouring pale colour is due to the absence of muscle. Their low-calorie diet obliges t is rather easy task to list threatened paler. myoglobin. Its blood irrigation, and them to be constantly searching for food. Iterrestrial tetrapods, insects and plants, hence its oxygen supply, is low. The The greater bulk of their muscles, if they The silvery glint of fish skin is produc­ as they can be seen and counted alive. greater part of the fish’s muscle works needed oxygen, would be of no use to ed by complete reflection of light from With fish, everything is more complicat­ Nils-Arvid Nilsson without consuming oxygen, but only for a them, since such great quantities of very thin flakes of guanine. These ed because they can rarely be seen and short time. Energy is generated by con­ oxygen could not be extracted from crystals are themselves colourless, but counted before they have been caught. verting glucose into lactic acid, a fermen­ the water. they alternate in the skin cells with They have since time immemorial been thin layers of cytoplasm. The thickness one of the most important sources of of the guanine and cytoplasm layers is food for mankind. Nowadays sport- such that all wavelengths of light are fishermen enjoy them in their fashion, uniformly reflected, producing a silvery but seldom without catching them. metallic shine. The guanine stack is so A list of the “Threatened Fish Species angled as to reflect the same amount of the World” easily becomes bizarre. of light as if there were no fish there. It might happen that the Icelandic To an observer from the side or form herring, once very important as nourish­ below, the fish is virtually invisible. ment and now severely threatened or Fish—like the other water creatures— extinct, is not mentioned, while more have made the best of their living or less obscure coregonids or cyprinids This has meant a lot of painstaking think­ conditions. Water is not a particularly may be listed. ing by taxonomists. Most important has hospitable medium; its inhabitants have been the experience of “sibling species”. - 6 * 4 A managed to adapt to it only over an These are species that are very closely unimaginably long time. The natural Geographical isolation related, so that they are more or less factors to which the organisms have impossible to distinguish morphologi­ had to adapt include: oxygen supply, According to Mayr and other experts cally, except, for instance, by physico­ density, viscosity, acidity, mineral con­ in spéciation geographical isolationchemical means, such as the electro­ Salmon tent and temperature, to name but a plays the main role in the origin of phoresis of enzymes, etc. However, (Drawing Christiane Daske) few. Human action is changing several species. No vertebrates other than fresh­ they are different in general ecological of these factors and pollution from water fish could be better examples patterns, and thus different in their sewage, toxins and waste of all kinds of the significance of geographical response to changes in their environ­ cannot but have a harmful effect. It is isolation, enclosed as they have been ment. In Europe, whitefish ( C o re g o n u s) incredibly naïve to assume that living in lakes or river systems for thousands and Arctic charr (Salvelinus) in pa rticu la r creatures can adapt quickly to such of years. In fact, every isolated popula­have been the subject of careful analysis new conditions. And that does not only tion is unique because of its adaptation both regarding physical and ecological Such scenes should disappear forever (Photo Verney) apply to water creatures. W.H. to the biotope of its origin. differences. Still more crucial is the phenomenon interesting Yugoslavian Salmothymus , subject to heavy water-level fluctuations. The most catastrophic effect on not of “subpopulations”, “stocks”, “races" or all Mediterranian endemic cyprinids. This means that the soft sediment, only freshwater fish, but nature in or “subspecies” of species that are able Apparently they are all worthy of pro­ plants, animals, etc. are eliminated general, is the increasing acidification to interbreed, but still remain separated tection, at least from a scientific point within the regulated zone, which in turn of land and water due to the emissions because of geographical isolation, hom­ of view, but personally I prefer to means an important loss of nourishment of sulphur from urban areas and heavy ing behaviour, etc. stress point 2 above, especially as fish and spawning sites within this area. industry. This means that industrial will become more and more important An attempt was made to compensate smoke, containing large quantities of For instance, homing is a very important in the future as food for the ever­ for the loss of food organisms by sulphur dioxide (S02) is spread all factor in keeping subpopulations of growing population of the Earth. transplanting glacial relictsMysis relicta over Europe. Because of prevailing Atlantic salmon Salmo( salar) and brown into the damaged areas. They are as a southwestern winds Scandinavia has tro u t (Salmo trutta) apart. It is a well- rule not dependent on the more shallow, been especially damaged by the deposi­ known fact that salmon return from the What threatens our freshwater regulated areas of the reservoirs, quickly tion of sulphur in the form of sulphuric Baltic to the rivers where they were fish populations? form very dense populations and provide acid (H2S04). once born or released as smolt. Brown an excellent source of food for some spe­ trout often appear to retain outlet- and Characteristically, different species of It was mentioned earlier that the con­ cies of fish that suffer from the loss of inlet-spawning populations that probably food caused by the water-level fluctua­ fish die at specific pH-values: never interbreed. One of the most struction of hydroelectric power plants often severely damages anadromous tions. interesting examples in Europe is that C ritical fish species, in particular, by disturbing S pecies of the land-locked salmon of Lake Pollution is a very complex concept pH -value Vänern, Sweden. This salmon appears migration or making it impossible. The that really requires a chapter of its own. Rutilus rutilus 5.5 nowadays as two distinct populations, dams not only hinder upstream migra­ Simply speaking, pollution is an adverse Phoximus phoximus 5.5 one originating from the main inlet, the tion, but are also often built in spots effect consisting of many different fac­ Salmo gairdneri 5.5 River Klarälven, the other from the River which were formerly important spawning tors, such as releasing excess nutrients Salvelinus alpinus 5.2 Gullspängsälven. Both populations are sites for the fish. (phosphorous, sulphate, nitrogen, chlo­ S alm o trutta 5.0 severely threatened by hydroelectric The interference with upstream migra­ ride, etc.) into a recipient lake. Some Coregonusalbula 5.0 development and pollution. They differ tion is sometimes partly compensated of these, such as sulphate, are poisonous Salvelinus fontinalis 4.5-5.0 in many ways, having different feeding for by the construction of fish ladders, in large amounts. In addition, more or Esox iucius 4.4-4.9 areas and above all, very different but the main means of compensation less alien toxic substances have pol- Perea fluviatilis 4.4-4.9 growth rates. The survival of the Gull­ A n g u illa a nguilla 4.0-4.4 spängsälven salmon is now subject to intense conservation efforts, in par­ Apparently, roach Rutilus ( rutilus) are ticular by preserving its spawning sites, the first fish to die, while perch (Perea as well as securing spawning products fluviatilis) and eel (Anguilla anguilla) for artificial breeding, followed by the are more resistant. Crayfish A ( stacus release of smolt. fluviatilis) are particularly sensitive, with In a similar way most salmon popula­ a critical pH-value of 6.0. tions of Sweden are being protected The effects of acid rain, with consequent by artificial means. decreases in pH, are problems that still The aims of nature conservation have need much further research. Acidifica­ for long basically been as follows: tion of catchment areas results in in­ 1. To conserve plant and animal popula­ creased leaching of heavy metals to tions as undisturbed as possible, to surface waters. High concentrations of enable future scientists to compare them cadmium (Cd), mercury (Hg) and alu­ to future populations (e.g. those affected minum (AI) have, for instance, been by human activities). observed in acidified lakes. 2. To conserve populations that could Thus, I would conclude by saying that freshwater fish are greatly threatened. be of future value, as food or for N.A.N. recreation, and 3. To ensure that the environment will be tolerable to surviving species, human beings included. Many species of fish are threatened i just on the borderline of their geo­ graphical distribution. For instance, in a recent list of threatened freshwater ...sometimes with man’s help (Photo Mario Broggi) fish in Sweden, the following species A Salmon on its way to spawn... were mentioned: Leucaspius delineatus, (Photo Hjalmar R. Bardarson) G udgeon (Gobio gobio ), Pelecus cultra- tus, Aspius aspius, Stone Loach (N em a- is fish culture, in which the fish are luted our waters, for instance DDT and chilus barbatulus) and Silurus gtanis. All raised from eggs to a stage of down­ sulphuric acid originating from western of these species have an eastern distri­ stream migration (the “smolt” stage). European industries. bution and are not threatened at all It has, for instance, been calculated The addition of excesses of nutrients except in south-eastern Scandinavia. that every fifth salmon caught in the is very much a matter of equilibrium: Baltic has been hatched and bred Apparently we have to reconsider the waters poor in nutrients (oligotrophic) artificially in hatcheries and released concept of “threatened species" in this sometimes benefit from the addition of in the mouth of the river to which context. Which species or subspecies is nutrients, while nutrient-rich lakes (eu- it is meant to return after 2-3 years in more worth of protection: the rare trophic), may easily die because of an the sea. salmon population in the River Gull­ overproduction of plants, oxygen defi­ spängsälven in Sweden, the valuable In contrast to the lower reaches of the cits, and the production of toxic hydro­ Danube salmon (Hucho hucho), the rivers, the uppermost reservoirs are gen sulphide (H2S). The Thames is alive

Derek Gren

he River Thames once supported 1953 - The clean-up began stabilised into a complex network of commercial fisheries of consider­ interdependent species. Table economic importance. Smelts Realising the unsatisfactory condition of Of the 104 fishes recorded, all but six from the Thames were plentiful at the country’s most famous river, in 1953 have been found by Thames Water Billingsgate fish market; 30 or 40 boats the London County Council embarked biologists since 1974 during routine working between Wandsworth and Ham­ on a mammoth scheme to rebuild and surveys of river life. Five species plus mersmith only a few miles upstream extend London’s major sewage treat­ the roach-bream hybrid were discovered from Westminster might catch 50,000 ment works, the chief polluters of the by earlier workers around 1970. in a day. Thames shads, flounders, Tham es. eels and whitebait were caught for During the peak periods, catches on a food and over one million lamperns The scheme was to take over 20 years power station’s intake screens a short were sold annually to Dutch fishermen to complete, during which time the distance below London’s major sewage Can we succeed, at least partly, in making good the damage we have done? Salmo salar,the Atlantic salmon, which disappeared from for use as bait. Even the occasional Greater London Council, and since works outfalls can total 10,000 fishes the Rhine some decades ago, may be poised for a come-back. Experts near Basle in Switzerland have started a 5-year scheme to release sturgeon was taken in the tideway. 1974, Thames Water carried through in a morning's sample and include over some 20,000 marked young salmon a year from fertilised Swedish eggs. After descending the Rhine to the sea, these salmon might, in the project which, at present day prices 30 different species. Where possible, two or three years’ time, return to spawn (Photo W. Hermann) cost some £200 million. these fish are returned live to the river to join the other millions of living 1810 - The fisheries destroyed This work has resulted in a greatly creatures in a stretch of river where less improved river and is recognised as the than 20 years ago no fish or large At the beginning of the nineteenth most successful campaign in the world invertebrate animals could survive. century several factors combined to to combat water pollution. destroy these fisheries. Thames Water’s role is now one of From about 1810 water closets became pollution control. On board a floating increasingly used in London, causing laboratory, teams of scientists and cesspits to overflow into town drains The river today biologists make regular sorties to which resulted in considerable pollu­ sample, analyse and record the condi­ tion of the river water and river life. tion of the London Thames and many The success of this clean-up campaign of its tributaries. was demonstrated initially by a gradual It is now Thames Water's task to main­ The growing number of industrial pre­ return of fishes and other marine life. tain the tidal Thames as the cleanest mises in London including slaughter The community as a whole has since metropolitan estuary in the world. D.G. New life for the Rhine houses, brew houses, coal wharfs, cow houses, tan pits, gun spinners and fish markets, all put their polluting wastes into the river. Sewage treatment works at Beckton, East London Another important factor which affected (Photo A. Handford) species such as lamperns, shads, sal­ Helga Inden he Rhine is one of mainland The only species that survive in rela­ mon and sea-trout was the construction E uro pe’s busiest w aterw ays. It is tively large quantities are those of the of weirs at and above Teddington pre­ Talso a living environment whose “white fish” varieties little prized for venting these fish from easily reaching once rich and varied flora and fauna food (roach) and a few moderately-rated their spawning grounds up river. Pol­ have, alas, greatly diminished since species (bream, perch, beaked carp). lution in the river became so severe the turn of the century. The more sought-after species, eel, that it was impassable to migratory trout, pike, grayling, carp and tench, fish. New methods of treating London’s It flows through a part of Germany are no longer found in commercial sewage rpade an improvement to the where both economic activity and quantities, except in a few stretches quality of the river water during the late population density are above average. of the river. Yet, as commercial fishing nineteenth century but sadly this im­ has declined, so recreational angling provement was short-lived. From about To the pollution which this causes (dis­ has constantly grown. 1920 the river became so polluted that charge of sewage, heavy metals and In order to halt the gradual destruction fish and marine life could not survive in chemicals, residue heat from power of the Rhine ecosystem and restore the metropolitan river from Gravesend to stations), engineering works designed conditions in which a diversified fauna Westminster. For the next 40 years to improve navigability by straightening can thrive, a number of laws and regula­ or so no fish were recorded in the the river’s course and regulating its flow tions have been enacted concerning London Thames. have added further harmful effects. sewage discharge, the use of detergents, Animal species, especially fish, have non-biodegradable effluent. These laws suffered badly from this degradation exist, it remains to enforce them firmly of their environment. and consistently. H.l. Biotopes Anton Lelek

t is common knowledge that fish environmental conditions. What this cannot live out of water. Books intended description of the changing face of a Ifor the general public usually show river fails to point out, however, is that brightly coloured fish swimming in here in Europe a skeleton is all that crystal-clear water. Such pictures are remains of what only decades ago was generally very striking, but give the a fully functional ecosystem. reader the impression that a fish has to be big, colourful, healthy and lively. Many publications aimed at people with What is known about a special interest in fish—fishermen, the environment of fish? nature-lovers, aquarium-keepers, or fish-eaters—set the picture of the fish Although a great deal is already known against a foreground or background: about the environment of fish, it is not the pike in a pond with water lilies enough to enable us to preserve all the floating on the surface, the brown trout fish in our lakes and rivers reliably in the rushing water of a stream, etc. and lastingly. The most important para­ Although these pictures are often largely meters of water are now measurable accurate, they show only a tiny fraction to the point of perfection; but their of the environment in which a fish must effects in ecological terms are not remain from the beginning of its life to fully understood, and the same applies its death. An egg measuring about to the influence of some harmful sub­ 1-5 mm produces a larva some 15 mm stances on the health of fish. long which can develop into an adult fish of some considerable size. To (Photos G. Kraczkwoski) A whole series of methods have been guarantee this development at every developed for breeding particular fish stage of the fish’s life a wide variety species, e.g. rainbow trout, carp and of aquatic biotopes is essential. Rivers’ salmon. In many cases, reproduction seasonal changes are particularly im­ in hatcheries has progressed to the portant. They have a special appeal: point that fry or larger fish are used romantic poets and composers were for stocking free-flowing stretches of early observers of the diversity of a rivers and lakes, e.g. pike, brown trout, river in its various forms, which they pike-perch, catfish, tench and some described in their own inimitable fashion. whitefish. These practical results are very important from the point of view of In extremely simplified terms, a river fishery. If we look at fish life as a whole, starts as a tiny stream whose source however, such breeding and stocking lies somewhere in the mountains. Swol­ measures have in most cases been only len with rainwater and melted snow, it marginally useful and, unfortunately, all merges with other streams and even­ too often harmful. tually becomes a small river, usually running through a fairly narrow valley. It is known that most fish can live and Finally it becomes a full-sized river, grow in moderately polluted water. The reducing its speed of flow according to tolerance limits have been identified in the volume of water and the terrain and many cases. The lasting existence of meandering slowly towards the sea many fish species is not guaranteed, through a flat landscape with wide flood- however, if one concentrates exclusively plains. From both the hydrological and on the quality of the water. The dif­ the limnological point of view, the upper ficulty is that the fish at each stage and lower reaches of a river are two of its development requires different quite different worlds, although there is aquatic and environmental conditions, a transitional zone in which they over­ and these can often differ considerably. lap. The differences include the amount To give an idea of the many different of water carried, the speed of the cur­ requirements of the various species, rent, the chemical make-up of the water, an attempt will be made below to des­ its temperature, the river profile, and cribe the life cycle of fish. The findings the shape of the river bottom or bed. of fundamental research have made a Similarly, changes are to be observed major contribution to this. It has been in the banks of a river, including the discovered that particular morphological vegetation and, not least, the surround­ structures reveal themselves through­ ing countryside. An additional factor out the development of every fish species is the variation of the water level ac­ and enable fish to survive in their cording to rainfall and the season. The respective biotopes. For example, fine creatures living in a river, including structures on the surface of fish eggs fish, have adapted to these various and their biochemical composition have They need been described, and the morphology of river beds existing today are only a the respiratory organs of fish larvae has fraction of what used to be available; been studied and explained. In many many habitats have disappeared alto­ species, the process whereby the larva gether. The turning of stretches of river becomes a young fish has been observ­ into drainage channels should be regard­ ed. It has emerged that every stage ed as the primary cause of the decline requires a different environment; this and gradual disappearance of many might be an aquatic plant or gravel bed, fish species. Efforts to improve water or it might be a question of water quality are by themselves insufficient depth, water temperature, current or the to achieve far-reaching success in such amount of oxygen in the water. The cases. habitat or ecotope of fish species is composed of a multitude of physical (properties of the water and form of What can be done? the substratum) and biological (suit­ able food) parameters, whose signific­ Fish were already regarded as useful ance can change according to the products of nature in ancient times. period of life. In practical fishery today they represent The life cycle of fishes can be divided a resource that is constantly renewed. into five periods: embryonic, larval, When the very existence of the fresh­ juvenile, adult and senescent. The em­ water fishing industry became increas­ bryonic period begins with the fertilisa­ ingly threatened by polluted and con­ tion of the egg; its characteristic feature taminated bodies of water, it endeavour­ is endogenous feeding from the ovum. ed to preserve some useful species. The larval period is typified by the The eel seemed to be best suited for transition from endogenous to exo­ this purpose, and its widespread intro­ genous feeding. This period lasts until duction proved very successful. After the metamorphosis into a fish. The first the last few years, in which efforts to bone tissue forms during this time. The improve water quality have, locally at continuous fin disappears and is replac­least, produced their first positive ed by actual fins. Similarly, the larva’s results, the intensive introduction of temporary respiratory organs (e.g. blood eels suddenly appears in quite a differ­ vessels in the continuous fin) recede ent light; in some biotopes where rem­ when gill development makes them nants of the original fauna have been superfluous. The juvenile period is mark­ able to continue reproducing naturally, ed by the fact that fully developed fins are the eel population has become so dense present and all temporary organs have that a large proportion of the fish been replaced by permanent ones. It lasts yield is decimated by them. This ap­ until gonad maturity. The characteristic plies not only to the few remaining At every stage in the fish’s life a wide variety of aquatic biotopes is essential features are rapid growth and often a backwaters, but also to the upper (Photo G. Kraczkowski) juvenile colouring. The adult period reaches of smallish rivers, the habitat begins with the attainment of sexual of graylings and trout. There it has been maturity. The often complex behaviour found that eels account for 20 % to in this stage of life is usually influenced 40 % of the total fish population. They by the highly complex reproductive not only compete with many fish species instinct. Body growth now slows down. for food, but also make a substantial In the senescent period, body cells are contribution to the depredation of the Department of Agriculture, 1982) de­ majority of cases they have already lived many cases. The weirs have been pre­ renewed only to a moderate extent, "smaller" species (loaches, bullheads, scribing possible ways of improving or in these biotopes, and so it is usually served, however, and for reasons of gamete development comes slowly to a minnows and, to some extent, lampreys) reorganising habitats in trout waters. a question of réintroduction in the hydrology and water management their halt and growth is minimal. and the young of the brown trout. One Once again we are concerned here course of environmental engineering demolition is virtually inconceivable. In solution would be to change conserva­ with fish species that are attractive to projects combined with improvements these cases, inordinately long slack- As reproduction marks the beginning tion methods, which have so far con­ people as objects of sport or sources to water quality. The provision of new, water habitats should be interrupted by of a new generation of fish, a suitable centrated too heavily on fish stocks. The of food. semi-natural habitats is a further re­ stretches with a stronger current, e.g. spawning ground must at the same time qu irem ent. through the creation of more gently eel was mentioned here only as an Habitats can almost certainly also be offer favourable conditions for the first sloping river beds (rock fills). The lower exam ple. created for those species which are It would seem that this problem could period of life. Studies of the conditions reaches of rivers are often navigable less well-known and unattractive from be solved most easily in fast-flowing governing successful reproduction have If we want to change the, in many and fringed with human settlements; the point of view of fishery. The first stretches of rivers (upper reaches or shown that many fish species require cases, highly unfavourable conditions hence they cannot be returned to their step in this direction should be to carry trout region). In the way of illustrative a series of very similar parameters, on affecting fauna composition in individual former state. Nevertheless, even here out an extensive survey of endangered material, there is still an abundance of the basis of which they can be divided bodies of water, environmental engineer­ there are numerous possibilities for fish species and describe their habitats natural biotopes in the mountains of up into specific reproductive groups. ing is the proper approach. The first preserving habitats or creating new in the light of the needs of the individual Europe which could be used as models Here are some examples: the alosa requirement is that water quality in ones, e.g. by reconnecting artificially species in its life cycle. A universal for the rehabilitation of spoilt stretches species are pelagic spawners, sturgeons polluted rivers should be improved. separated backwaters and ponds to the model for all the various kinds of of rivers. In the middle stretches of and some coregonidae rock and gravel Unlike this perfectly attainable goal, river. habitats is not to be recommended. It rivers, known as the grayling and barbel spawners, carps plant spawners, gud­the idea of returning all rivers to their seems more useful first to fill in the region, there are often already limited In the last analysis, it should be left geons sand spawners, and pike-perches original state is unrealistic. It has been gaps still remaining in our knowledge opportunities for favourably influencing to fishery biologists to draw up environ­ and sticklebacks nest spawners. shown in practice that it is possible to restore individual habitats and even of the life history of certain fish species or transforming the condition brought mental engineering projects and take For this reason, the spawning ground increase the range of species present. (e.g. the zingel or the groundling). The about by human activity. Rivers were responsibility for managing groups of should be regarded as a primary con­ The intensity with which work is pro­ appropriate species should be intro­ usually dammed up here in the past to species in their proper biotopes. A.L. dition for natural reproduction. Let us ceeding in this field is apparent from duced into habitats which seem suit­ produce energy. The relics, e.g. water not forget that the kinds of lake and a list of publications (800 papers, US able for permanent settlement. In the mills and sawmills, now lie abandoned in There are seven species of European has one of the lowest salmon stock in sturgeon, but six are all but confined Europe; the total European catch is of All is not lost to the USSR; only one (A cip e n se r the order of 13,300 tonnes. stu rio ) lives in the Atlantic, the Mediter­ ranean and the Black Sea. This sturgeon There are ten species of shad in Europe, ascends freshwater rivers in spring to but eight of them are only found in spawn; the eggs (known as caviar) are the internal waters of the USSR. Of the two species found in the Atlantic and deposited on gravelly riverbeds at a Mediterranean, we shall mention only depth of 6 to 8 m and attach themselves to stones or aquatic plants. The young the most important, the Allis shad fish live in freshwater rivers or estuaries (Alosa alosa). Henri Hoestlandt until the age of three years, before This shad enters fresh water in spring going downstream to the sea. Growth to deposit eggs in the clear water of at sea, in water 20 to 50 m deep, gravel-bottomed streams. Most kelts is rapid; the sturgeon reaches a length die after spawning. The young fish grow hat the living world of which we is practically on a human scale; this is of 2.5 m in about 40 years. Males are rapidly (9-13 cm in one year) and go Sturgeon are protected in France since 1982. When accidentally caught, they are either are part has evolved with the pas­ particularly the case as regards a mature at about 14 years, females at down to the sea at the age of one released or transferred to fishponds in the hope that they reproduce sage of time is an accepted fact number of vanishing species in many about 18. After spawning, the adult fish T or two years. Growth continues at sea (Photo Jean-Louis Duzert) and one which scientists have clearly biotopes. return to the sea. (at depths of 200-300 m) over a period proved. That biological evolution is con­ Among the threatened species of fresh­ of 3-5 years and sometimes more. tinuing is also accepted in theory, water fish in Europe, a distinction may This sturgeon has become rare, if not although in practice we think we live in extremely rare. It is still found in the This shad has become rare in the be drawn between those of little or no rivers of northern and northwestern a biological world which is stable and value as food and the rest. The former Gironde estuary, the Guadalquivir, Lake fixed, in other words, changeless. It is Ladoga and the Black Sea. Its rarity Europe and around the Mediterranean. are of interest only to ichthyologists, pollution. The benthos provides a con­ pollution by more stringent water treat­ true that natural evolution is slow and is illustrated by the fact that 250 sturgeon It is still fairly common in the west while the latter are of interest to the siderable proportion of the food of young ment. Care must also be taken to prevent that it is difficult to observe specific were caught in the Gironde estuary in and south-west of Europe—in the Loire, consumers we all are. migrating fish. agricultural fertilisers, pesticides and examples of evolution during a human 1953 and only 4 in 1983; it is under­ Dordogne, Garonne, Guadalquivir, herbicides from seeping into our fresh lifetime or even over a few hundred We shall mention very briefly the spe­ standable that fishing for sturgeon is Minho, Douro and Tagus rivers. For water. As a consolation, we may men­ years. Furthermore, the evolution caus­ cies in the first group and go into forbidden in France at present. example, 500 tonnes of shad were Mention should also be made of the tion the example of the Thames where ed directly or indirectly by mankind greater detail on those in the second, caught in the Dordogne and Garonne considerable obstacles to migration beginning with general biological as­ The Atlantic salmon (Salmo salar) enters rivers in 1978. caused by the many dams whose effects no salmon had been caught for 160 years are only seen at a later stage. While but where, in 1973, one was taken pects, then pointing to the causes for fresh water in Europe and North America Of the species which are still abundant fish ladders are often provided, even 16 miles upstream from London Bridge. the reduction in their numbers, and to spawn, usually in winter. The female but diminishing in numbers, mention the best of them do not allow all finally mentioning ways of trying to con­ hollows out a "nest" in the gravel bed may be made of the common eel Fishing regulations are called for at spawning fish to pass; the result is serve them. and the male fertilises the eggs shed by which lives in fresh water and reproduces both national and European level and the more or less rapid decrease in the female. Few adult fish (approximately at sea (20,000 tonnes caught in 1963, should take account of recent biological numbers of anadromous species. Sturgeon (Photo Jean-Louis Duzert) 5 %) return to the sea to begin a second and 13,000 tonnes in 1981). Other knowledge of the species in question. Fish declining in numbers or third spawning cycle. examples are the common pike and the Lastly, mention should be made of over­ To take just one example, the salmon: European brown trout Salmo ( trutta ), fishing on both an individual and more we know that its rarity in France is We shall give two examples of fishes The dark-coloured young salmon, called which are still found in our freshwater particularly an industrial basis; increas­largely due to the inadequacy of with no value as food. parr, spend one to eight years in fresh rivers thanks only to fish farming. ingly sophisticated equipment is used regulations in the relatively recent past, water, depending on latitude; they then The first is the bittlering ( R hodeus for the latter—for example, Danish but that present regulations augur a go down to the sea in spring, taking am arus), found in central and western fishermen catch salmon in the fatten­ brighter future. On a European scale, on a silver livery—they are now called Europe. A particular characteristic of Causes of diminishing numbers ing area off Greenland with extremely it is gratifying that the Danes have smolts and are 12-16 cm long. It has this small fish (6-7 cm long) is that effective nets made of single-strand agreed to reduce their fishing in the been known for a number of years that it deposits its eggs in freshwater mus­ These apply mainly to the three ana­ nylon which are almost invisible to the salmon fattening area off Greenland salmon grow at sea for a period of one sels (U nio and A no do nta), w ere the dromous species described but to a fish. (1,191 tonnes at present); this will or two years in special "fattening fry remain for three to four weeks large extent to the other dwindling ensure the salmon’s continuing presence areas”, three of which are well known before swimming away. These large species too. in the rivers of Europe and hence in and account for 80 % of all salmon. mussels are declining in numbers as Hopes for recovery the fattening areas. They are located off the west coast The first cause relates to the spawning a result of the deterioration in the It is extremely fortunate that at present of Greenland, in the Norwegian Sea, grounds in gravelly or rocky riverbeds natural environment, pollution and, in Our hopes may be pinned on human the European Community is aware of and near the Faeroe Islands. When going in well-oxygenated clear water. There particular, predation by the coypu and activity in three main directions: fish the problem of reconstituting fish stocks. upstream to spawn, the salmon use are fewer and fewer such areas; they musk rat. This is therefore leading farming, water purification, and nationalWhile it is not possible to hope for a their keen sense of smell to return to tend to become choked because of the indirectly to the slow disappearance of and European regulations. complete return to the past (evolution the freshwater area where they were numerous dams which slow down the the bitterling. is not a backwards movement), we may hatched (“homing”); the memory of the current further upstream and cause Firstly we must be able to reproduce nevertheless achieve a new biological The second example is the river blenny smell is “registered” during the smolt silting, because of the many gravel threatened species artificially and often balance as a result of the work of (Blennius fluviatilis ), w hich is d is ­ stage. Navigational errors are very rare. workings which give rise to the forma­ must make provision fortheearlydevelop tributed throughout the periphery of the tion of silty or muddy riverbeds, and ment of the young fish; this can be done various scientific and administrative because of the eutrophication of the by placing the fertilised eggs or young bodies in order to satisfy human require­ western Mediterranean. This fish, 10 cm In the past salmon were abundant water which increases organic and algal fish in a suitable aquatic medium. This ments both in terms of food and leisure. long, needs pure water on a stony or around the coast of Europe. The fol­ deposits. The consequence is the death method has already been used for trout H.H. rocky bed. Because of its ecological lowing fact is always quoted in this (using Vibert boxes, for example), sal­ demands and the vulnerability of its respect: in Brittany, agricultural workers’ of many eggs, which become coated with silt, mud or organic deposits and mon and pike, but should be developed spawn, this species is vanishing. contracts used to stipulate that salmon are therefore starved of the oxygen further. Improved techniques should Among the species of interest to us as could not be served at meals more than necessary for their development. make this possible for the shad and food we shall give three main examples two or three times a week. That was even the sturgeon. —the sturgeon, the salmon and the shad. quite understandable in the 18th cen­ The second cause is a slowing down All three are anadromous migrating tury, when 4,000 tonnes of salmon were in growth caused by the impoverish­ Secondly, water purification techniques species, in other words they reproduce caught off Brittany, but in 1970 the total ment of the benthos. This is due to must be intensified through more ef­ in fresh water but spend most of their French catch was less than 30 tonnes; the growing scarcity of rocky or stony fective anti-pollution measures. It is growing time at sea. it is true that French fresh water now riverbeds and t< physical and chemical essential to reduce urban and industrial The result is a faster intake of such substances as pesticides and heavy metal salts, which become life-threaten­ ing even at concentrations not con­ sidered critical under normal conditions.

The concentration of organic waste can Pollution Enrico G e/os/ thus reach levels damaging to the delicate oxygen requirement equilibrium and the strenuous respiratory process, and can become lethal.

By virtue of the natural oxidation and oxidation-reduction processes perform­ ed by the micro-organisms which break systems and their interdependence—for their body temperature varies with that down organic matter, organic waste they are obviously interrelated. On the of the water. Consequently, it is only depletes the water of the oxygen es­ other hand, we have yet to see the within specific temperature ranges that sential to the survival of fish, while emergence of a political awareness of their enzymatic processes can func­ at the same time the exothermic reac­ the problem, which has inherent social tion efficiently, and their metabolism tions of the oxidation processes actually and hence political implications, and and very survival therefore depend raise the temperature of the water. As the resources available for the develop­ heavily on the temperature of the the concentration of organic waste rises, ment of this science and for environ­ environment in which they live. it becomes difficult, if not outright mental protection are almost always he galaxy of ecosystems making A distinction can be drawn here between impossible, for the fish to survive: modest and invariably inadequate and up our planet is amazingly well- eurythermal species, which readily adapt asphyxia occurs. badly distributed. Yet the usefulness equipped, with its biological chain, to temperature fluctuations, albeit within T of such research and the urgent need atmospheric agents and transforma­ limits, and the more numerous steno­ In connection with respiratory processes, to expand and co-ordinate it and trans­ tion and regeneration cycles, to cope thermal species, which can survive only we must not forget that toxic substances late its findings into practical projects with all pollution processes of natural within a very restricted temperature interfere with the transport of oxygen are undeniable. origin. The mechanisms essential to range. (Photo F. Bibal, Unesco) t0 tissues since they directly affect its biological equilibrium are now under The hiqh price that man will have to pay for damage done to the environment is often overlooked the blood pigments, just as nitrites serious threat, however, from a form As far as respiration is concerned, it affect haemoglobin. of chemical and biological warfare The toxic effects of pollution should be pointed out that oxygen dif­ (Photo G. Kraczkowski) that is an iniquitous by-product of pro­ fuses very slowly in water and that the Fluctuations in pH, even if they remain gress. As we have briefly seen, many extremely oxygen content of saturated water is within limits acceptable to fish (normally complex factors and numerous sub­ about 20 times lower than that of air. between 5 and 9), affect the toxicity One of the most harmful practices is stances are responsible for water pol­ In order to extract and use the oxygen, of certain pollutants by accelerating the use of large quantities of detergents lution, with varying effects on the fish therefore have to take in a much their dissolution. This is true in the containing a high concentration of environment. They include oxygen con­ greater volume of water through their case of ammonium salts, the toxicity phosphates, not so much for washing centration, pH (which I shall mention gills than the volume of air required of which increases as the pH rises, purposes as to counteract the salts briefly since the importance of acid by land vertebrates. Furthermore, since and cyanides, which are more toxic at in hard water and soften it for house­ rain cannot be overlooked), carbon the density and viscosity of water are low pH values. hold use. dioxide, surface tension, osmotic pres­ infinitely greater than those of air, fish Admittedly, immediate results are as­ sure, toxic substances, organic waste, have to make an enormous effort to sured, but the consequences are much and so forth, not to mention a factor extract oxygen from water for respira­ more drastic than the initial problem: of vital importance to fish—temperature. tion. Damage to fish and the fishing the excessive level of phosphorus- Once this has been understood, we can In fact, respiration accounts for about industry containing compounds causes algae to boil down the assessment of the capacity 20 % of the total oxygen consumed for proliferate, giving rise to a state of eutro­ of water to support life to the evaluation the vital processes: about 10 times as This brief review cannot be concluded phication which kills off living organisms of three fundamental factors, for it is much as in the case of land mam­ without a reference to the damage to in lakes and seas. The damage definitely not possible to analyse them all here: mals, for instance. the fishing industry. Fish which have outweighs the benefits, as is all too - the quantity of dissolved oxygen; come into contact with acids, suspended often the case with production processes - temperature and its fluctuations; If we continue to bear our basic para­ matter, caustic substances, etc., may (there are well-known examples). Such - the presence of toxic substances of meters in mind, it becomes obvious that suffer skin lesions and abrasions which, processes are accepted with alarming various kinds. a protracted temperature rise will, since lacking a protective layer of mucus, short-sightedness for the sake of pro­ less oxygen can dissolve in the water, are rapidly invaded by fungi and bacteria We shall therefore examine the toxic gress and what is taken for well­ force the fish to speed up its respiratory which irreversibly damage their viability effects of pollution on fish, taking being, while the high price that man process at precisely the time when the and appearance. will pay for the damage to the environ­ account of two parameters crucial tooxygen level is decreasing. ment is overlooked. the survival of aquatic organisms: tem­ Damage is also caused by mineral oils, The acceleration of the respiratory pro­ perature and the dissolved oxygen con­ phenols, ethers, sulphides, mercaptans, cess increases the intake of any toxic centration. These parameters are, more­ etc., which although they do not, at low substances present in the water. The over, closely interrelated since, as the concentrations, threaten the survival of The need for political awareness very presence of these substances can temperature rises, the quantity of oxygen the fish, give it such an unpleasant smell affect the mechanisms of respiration. In which can normally dissolve in the water and taste that it is certainly not to be The toxic effects of environmental pol­ fish the exchange of gases takes place decreases. That is why cool water is recommended as food. Moreover, the lution, which has now spread to all parts mainly at the membranes of the gills more highly oxygenated than warmer fish keeps less well and, being quickly of the biosphere, have been known for by the ordinary mechanism of respira­ water. perishable, loses still more of its com­ some time and are being widely in­ tion, which can be summed up as the mercial values. vestigated. Their study has given birth The water temperature, which has a permeation of biological membranes by to the new science of ecotoxicology, definite effect on the oxygen concentra­ gases. one of the aims of which is to further tion, is of crucial importance to the These assertions are fully borne out by our as yet incomplete knowledge about metabolism of the various species of All surfactants, e.g. detergents, affect one current example of damage to fish in the extremely complex operation of eco­ fish, for fish are cold-blooded—that is, the permeability of these membranes. the natural environment, in Lake Nemi. Lake Nemi Lake Nemi is a small volcanic lake in Life-giving rain? the group of craters in the Alban hills near Rome. It is surrounded by woods and farm­ land. It has no tributaries: all its water comes from the catchment basin and from underwater springs, which are not always active.

At the beginning of the century the lake William Dickson was classified as oligotrophic; the oxygen concentration was at saturation point virtually throughout the mass of water, the levels of nutrient nitrogenous and round and inland waters in percentage of acid lakes is lower. The be secondary effects, caused by chang­ phosphorus-containing salts were within Sweden have been exposed to extent of the acidification, however, is ing nutrient, competitive and predatory normal limits and there was little rapidly increasing supplies of acid more difficult to estimate here, primarily conditions. plankton. G for at least twenty years. This is because pH fluctuations in smaller lakes According to local consultants, acidifica­ The fish present in the lake included primarily due to the increased burning and running water can be very large. tion has caused the Swedish crayfish many temperate-water cyprinids, eels, of fossil fuels. The greatest atmo­ During periods of melting snow, fatally (Astacus astacus) to decline in as many pike, perch and a stenothermal Nordic spheric acid fallout takes place in the low pH values can occur for a short as 20 % to 30 % of the total number species of whitefish (Coregonus) intro­ south-west. Here the precipitation is at time even in normally well-buffered of lakes in south-western and central duced in 1925, which thrived in the least ten times more acid than it is w aters. Sweden. The total lake area which is assumed to have been before industrial­ lake, since in summer it was able to find The total number of acid lakes in known to be affected has been calculat­ isation. cooler, adequately oxygenated deep ma Sweden is at least 14,000 in phase 2, ed at about 115,000 hectares, plus water which suited its living require­ The bedrock in the greater part of and about 4,000 in phase 3. about 150,000 hectares which are as­ m ents. Sweden offers poor protection against The most sensitive lakes in southern sumed to be affected. acid fallout, so many lakes and rivers Between 1928 and 1932 the water level Sweden probably became acid during In the south-west, the sensitive and have become acidified. was lowered by about 20 metres in the period 1950-1970, i.e. when the formerly very common roach has declin­ order to salvage two ancient Roman Acidification can be divided into three atmospheric deposits of sulphur in­ ed in about 2,000 lakes larger than one ships. It was then gradually allowed to phases. During the first phase, the pH creased most. The pH values have in hectare, which means in about 5 % of rise again. The new physical and value is fairly high and stable. The most cases decreased in the sensitive all the lakes in that area. chemical conditions resulting from the hydrogen ions in the precipitation are lakes, even during the seventies, but In southern and central Sweden, fish drainage of the lake made it more absorbed by the bicarbonate buffer the rate of acidification seems to have stocks in about 2,500 lakes have been eutrophic than before. system. The second phase begins when been somewhat reduced. damaged by acidification and in a further this buffer system no longer functions In 1969 the Rome Ichthyogenic Estab­ 6,500 the stocks are assumed to have all the time and the pH values fall lishment (Stabilimento Ittiogenico di declined. This number (9,000) cor­ below 5.5. Organisms living in the Biological effects Roma), embarking on a series of responds to about 10 % of all the lakes waters are now affected and episodic studies of the fish in the lake, found in Sweden and 10 % of the total lake This fisherman still has a nice catch but for how long? deaths occur in fish populations. During Acidification leads to a decreasing num­ that conditions in general were still (Photo Alain Kayser) area of the country. phase three the pH value stabilise at ber of species of organisms at all within normal limits and that conditions about 4.5 even if the precipitation is trophic levels in the ecosystem. A thorough knowledge of the effects in summer were still suitable for white- more acid. Aluminium and humus in of acidification in lake-rich northern fish, which could find cool, sufficiently Typical effects are a massive invasion the soil and water act as a buffer Sweden is still lacking. We know, how­ oxygenated water at a depth of of species of sphagnum, and an increas­ system at this stage. With the decreas­ ever, that many small and normally 15 m etres. ing accumulation of organic debris ing pH values, there is an increase in reduces mineralisation, especially in well-buffered streams in that area may have very low pH values and high The productivity of the lake, which was the content of many metals in the the littoral areas. fished to the full, was the highest waters, especially the aluminium con­ concentrations of aluminium during the in Italy for natural waters: about 200 kg tent. These indirect chemical changes The most sensitive species in fish in period of melting snow. Sweden are roach and minnow(P hoxi- of fish per hectare per year, 80 % of it proliferation of algae, whose decomposi­The Ichthyogenic Establishment is ex­ in the acidified waters may cause more nus phoxinus), for which pH values accounted for by whitefish alone. This tion and fermentation had virtually de­ perimenting with the introduction of a severe biological effects than the in­ around 5.5 seem critical to reproduc­ excellent yield quickly fell off, however, pleted the water of oxygen below a depth South American species of fish, O don- crease of the hydrogen ion itself. Liming against acidification tion. Somewhat less sensitive are many as a result of the ever-increasing input of a few metres by summer 1975. As a testhes bonariensis, with a view to species of salmonids. Pike, perch and of organic waste from the sewers of result, virtually all the fish were killed repairing the damage, at least in part. above all eel seem to be the most In an attempt to combat acidification, Nemi and Genzano and sewage from a off. All the whitefish died and only Acidified areas This fish, which belongs to the Atheri- resistant. a large-scale liming programme has 1,200-bed geriatric hospital. This proved a few fish of the more resistant species nidae family, is aurythermal and ex­ been started. About 3,000 lakes have definitely too much for the small lake, survived in a weakened state which The majority of the acid lakes (pH Effects of acidification may be ob­ tremely resistant to change in en­ been limed over the last few years. which was also receiving water that had made them prone to attack by fungi value less than 5) are situated in the served at pH values which are not vironment, and has good organoleptic Much of the cost is met by the State: leached fertilisers and pesticides out and bacteria, present in abundance in south-western part of the country. With toxic to most freshwater organisms. properties. The results have been en­ this year 70 million Swedish kroner of the surrounding farmland. the severely damaged environment. few exceptions, these must be regarded Aluminium, however, has been proved couraging, but the deterioration of the (8.5 million US dollars) is being spent. as acidified. In the west coast area, to cause fish mortality even in rather The first visible sign that the hydro- In the years that followed there were environment last year caused the loss Although the biological effects are about 75 % of the lakes have pH values low concentrations and to have maxi­ biological balance had been destroyed periodical improvements as a result of a large proportion of the lake’s stock positive, this chemical treatment can lower than 5.5 during at least some part mum toxicity at pH levels slightly above appeared in 1974, when the surface of of the introduction of restrictions on of this species. Nevertheless, the modest only be regarded as a temporary solu­ of the year and 33 % have reached the 5.0. the lake began to turn red as a result polluting discharges, but organic pollu­ number of survivors will breed and it tion. The problem can only be finally third phase (pH value less than 5 during of a phenomenon known as “water tion is now a constant feature of Lake will be possible to repopulate the lake If certain key organisms are wiped out solved by a sharp reduction in acid summer). In other sensitive parts of bloom”, caused by the proliferation of Nemi, the oxygen depletion in summer and follow up the results of the ex­ by aluminium poisoning, or by some emissions to the atmosphere. The southern Sweden, about 50 % of the the blue-green alga “Oscillatoria ru- being such that whitefish can no longer periment, which were encouraging. other agent, this will have an effect deposits of sulphur must be reduced lakes are acidified. bescens". The situation worsened the survive. Among other things, this has on the whole ecosystem. Therefore many to less than 0.5 g per square metre/ following year: there was a massive seriously affected the fishing industry. E.G. In the northern part of the country, the effects of acidification are believed to year. W.D. trout’s migration route through affluents tocking natural waters with hat­ After World War II the practice of stock­ to its breeding areas may be cut off by chery-reared individuals of autoch­ ing migratory young + 2 year old salmon the construction of dams and other Stocking Sthonous species has rocketed in ("smolts") near the mouth of the river developments. p o p u la rity since W orld W ar II. The proved highly successful. Stocking with maintenance and enhancement of fish­ “smolts” is now practised worldwide. ery yields is the goal aimed at in general. Other reputedly successful stockings are and Or in other words: to maintain the those of elvers, common carp and, in Trends in fishing population density at a maximum car­some countries, coregonus. These suc­ rying capacity of a water system or at cesses, most of which concern species The perch is the species most sought- least to prevent this density decreas­ which no longer reproduce success­ re-stockinging below a certain limit often set fully under prevailing natural conditions, after by fishermen, especially in Switzer­ land. The powan, the lake trout, the pike according to economic criteria. possibly led to the feeling that stocking in general is a successful tool in fishery and the char are also caught regularly. At first stocking was practised to management. Because of eutrophication (the enrich­ counteract the negative impact caused ment of the lake water by domestic by habitat modifications due to human Whatever the reason, nowadays prac­ and agricultural fertilisers) and con­ influence. More recently, the fishing tically all European countries practise siderable improvements in fishing meth­ pressure being such that populations stocking with a wide variety of species. M. P. Grimm ods, the yield from professional fishing can be overfished, to prevent depletion. Evaluations however are few and the increased regularly for decades to reach In general the lowest cost/benefit ratio assessment of success or failure is often some 1,500 tm in the years 1971 to is aimed at; thus, individuals stocked controversial. 1975 (23.7 kg/ha). This progression, are of the smallest ecologically accept­ due mainly to a dramatic increase in able size and the natural productivity perch-fishing, was brought to a sudden of a water system is used to achieve, The introduction of allochthonous halt in 1977. The fish yield, especially by growth, the aforementioned carrying species that of professional fishermen, plum­ capacity. meted. The perch population only re­ established itself in 1983 and more so Recently we know of stockings where in 1984. these cost/benefit ratios are considered The oldest large-scale introduction in less important, e.g. the stocking of Europe concerns the distribution of the artificially propagated individuals tocommon carp. Most introductions of conserve a threatened species, the re­ allochthonous species have been much Franco-Swiss co-operation population of water systems after en­ more recent, occurring mainly over the vironmental disasters, such as the spil­ last two or three decades. The manage­ ling of toxic substances. Before the Franco-Swiss Agreement on ment goal is to improve fishery revenues. fishing in Lake Geneva entered into Often it is supposed that an eco­ force in 1983, the authorities in the system, whether or not changed by man- Salmon fry in the Rhine (Photo Ludwig Bernauer) two countries agreed on co-ordinated made factors, harbours vacant niches action to control fishing in Lake Geneva. and therefore is not fully exploited by Measures especially designed to restrict The release of salmon fry in the river the fish population present. The intro­ perch fishing were decided upon. These Rhine tributaries was one of the first duction of salmonid species in Arctic will come into effect in 1985. A work­ large-scale stockings in natural water lakes in Sweden, where no predator ing group of scientists from both coun­ systems in Europe. These stockings fish species was present, and the tries was also formed. Its brief is to took place from the second half of the introduction of silver carp (a phyto­ Bernard Büttiker establish better co-ordination in re­ last century, but without achieving their phagous species) in the heavily eutro- search into the fish of Lake Geneva, and objective which was to stop the declin­ phicated Lake Balaton are instances to provide the necessary scientific basis ing numbers of adult salmon returning of such attempted niche-filling intro­ for fishing management. in the home-run to their rivers of origin. ductions.

Fish-breeding facilitates the re-stocking of lakes and watercourses Prospects for the future (Photo 0. V. B.-Foto)

A better knowledge of the biology of these fish must be gained, so that their ake Geneva is the largest mass of On the other hand, 11 species have numbers may be controlled, to ensure a water in central Europe. It is up to been introduced into the Lake Geneva good long-term yield. This will prevent 300 m deep, with a surface area of basin over the last few hundred years. L the lake from being over-fished. But 582 km2 and it contains 89 km3 of Two indigenous species (or races) of how is the consumer to be convinced water. However, the variety of fish in coregonus of significant economic value, that fish other than perch, all equally its waters, 25 species, is very low the "fera" and the “gravenche” dis­ tasty, live in Lake Geneva? In the past, compared to other regions of Europe, appeared because of over-fishing at the such attempts to inform the public have especially the Danube basin or the beginning of the century. These were often met with failure. Iberian peninsula. Many species which replaced by the powan (C oregonus inhabited central Europe before the lavaretus) from Lake Neuchâtel. The authorities are also concerned with last ice age, when there was a mucn protecting the lake’s environment. De­ greater variety of fish than there is Two salmonids, the lake trout and the terioration in the quality of the water today, disappeared when the continent char are surviving well at the moment. has reached a critical stage, and the was invaded by glaciers. Then geo­ However, the natural spawning grounds state of the lake must be improved graphical barriers hindered the restock­ of these two species, both of which are immediately, before a point of no return ing of the region. The Lake Geneva very valuable as wildlife and for fishing, is reached. Finally, the remnants of the basin was especially isolated because are under threat: those o f the char are natural shore-line must be saved, and several migratory species were not able likely to be buried under mud as a con­ the fishes’ spawning grounds preserved. to swim up the Rhone to the lake. sequence of eutrophication, whilst the B.B. Man-made lakes Unintended introductions also occur. Measured as the frequency of occur- The biomass of pike smaller than The penetrations of the two marine rence of marked mature individuals, 40 cm, that of one-summer-old indi- species sea lamprey and alewife in the originally stocked as fingerlings, the viduals (15-35 cm) especially, is highly Great Lakes (US) is a notorious acci­ stocking of pike was considered sue- negatively correlated with the biomass dental introduction. Introductions by cessful by European and American fish- of older and larger ones. This quan- ater is, undoubtedly, one of the prehistoric times. The history of stew negligence established abundant roach ery managers. titative relationship demonstrates that Jan Kleinert essentials to life on the Earth’s ponds or fish farming in Europe ap­ populations in Ireland (continental pike the stocking of pike was useless. The surface. A pond, or for that parently began in the 13th century, anglers released the remains of their high aforementioned frequency of oc­ W matter any body of still water is, or when fishing became commercial and imported live-bait stock). The release currence of individuals stocked as could be, an example of a self-suf­ fish became something that could be of ornamental fishes established local fingerlings turned out to be a displace­ ficient climax ecosystem, occupied by a exchanged or sold in the market. This populations of such fish as guppies and ment of natural recruited pike by stocked wide scale of producers and consumers. encouraged the building of artificial pumpkinseed (Eupomotis gibbosus). An individuals. A displacement—no con­ It is often the only place left for ponds where larger, faster-growing, intentional, illegal introduction estab­ trib u tio n . wildlife, an oasis of stillness. productive fish species, which also lished a pike-perch population in East The results of this long-term research tasted good, could be selected, studied Anglia (UK). Nevertheless, this function of water showed that the bottleneck in the recruit­ and bred. Nevertheless, consumption is bodies may be compromised if they ment of young pike is the surface expected to at least double in Czecho­ are located in suburban areas, in easily vegetated area—the growing-up habitat. slovakia, where at present it is 0.7 kg per accessible, frequently visited sites, or The effects of introductions Thus the decline in pike populations inhabitant and the annual yield reaches in the vicinity of sources of pollution, or stocking can be stopped by protection of the 10,000 tonnes. eutrophication and other kinds of dis­ aquatic vegetation—immersed plants, Fish farming is developed in exploited As with introductions of allochthonous turbance. The coastal zone often shows especially. gravel pits, old river beds and other species in general, those of fish spe­ signs of the indifference of visitors, The highest density of pike often wanted hollows filled by surface or ground cies also vary in their effect from com­ including fishermen, who carelessly leave in fishery management is likely to be water. As an example, Slovakia has plete disaster (as was the case with their rubbish about, or even use the reached in shallow waters with a surface water to wash their cars. The importance now almost 30,000 hectares and Bo­ the penetration of sea lamprey and vegetated area spread over 25 % of the of environmental education, or rather hemia more than 50,000 hectares of alewife into the Great Lakes) to oc­ total surface. Thus efficient pike manage­ the lack of it, is evident here, though artificial still water reservoirs. (They casional complete success. Introduced ment entails effective protection of a few ponds, lakes and watercourses are mostly under the control and man­ allochthones unable to reproduce in aquatic vegetation. agement of fishing associations, though their new environment (the white amur are already equipped with nature trails, some are state-owned.) Intensive and in north-west Europe) belong to the facilities for bird-watching and so on... As mentioned earlier the effects of controlled farming allows the production former category. stocking are in general not quantifiable, of 460 kg of fish per hectare per year. Often the beneficial and/or detrimental not only on the autecological, but The importance of fishing To increase the productivity of the pond effects are disputable but it appears especially on the synecological level. ecosystem and the fish stock, water is that deleterious effects on native fish It should be realised that, given the sometimes fertilised with manure, or communities can all too often be economic interest prevailing in most Fishing for food in running as well as improved by lime. This is usually done observed. fisheries, managers will often stock a in still waters has been practised since species reasoning that it is useful unless Acknowledging these disadvantages proved otherwise. member countries of the European Inland Fisheries Advisory Committee Both from the point of view of effective adopted—in close co-operation with nature conservation and of efficient the International Council for the Ex­ management of fish stocks this stand­ Artificial ponds often become sites of great natural value ploration of the Sea—a code of practice point is questionable. Realising this, (Photo Jan Baltus) by which the risk of adverse effects the member countries of the European of introductions can be reduced to Inland Fisheries Organisation establish­ tolerable levels. ed a Working Party on Stocking. The terms of reference include “encourag­ History proves that once a species has ing co-operation in research”. Hopefully passed a border it should be considered (Photo o. V.B.-Foto) the need for this research will also be as having been introduced in a country. understood by other interested parties In this respect the large-scale uncontrol­ and to such an extent that funds can led transfer of ornamental fishes which The numerical decline of the Dutch be made available. M.P.G. is common practice in most countries pike population and the shrinking of is of gre at concern. its distribution area were attributed to a marked reduction of the preferred As mentioned before, the effects of intro­ spawning habitat, the freshly inundated ductions are often uncertain and debat­ vegetation of grasslands, due mainly able. The same holds for stocking with to the strict regulation of the water autochthonous species. Due to our lack level preventing spring floods. of knowledge of the population dynam­ ics of virtually all fish species, the By monitoring numbers per age-and- amplitude of the numerical yearclass- length classes over an 8-year period strength in time is unpredictable. Thus and by determining their habitat pre­ the effects of stocking cannot be quan­ ference, another picture of the pike tified. The importance of this biological was built up. Within natural populations information is illustrated by an evalua­ pike up to 40-60 cm are associated tion of the stocking of artificially pro­ with the aquatic vegetation to such a pagated Northern pike fingerlings by degree that at the end of each summer the Organisation for the Improvement a constant biomass of 80-150 kg/ha of Inland Fisheries in the Netherlands. vegetated area of these pike is present. in the spring to promote the growth those that live in rivers, face an un­ of phytoplankton and to adjust the pH certain fate because of permanent and chemical balance. water pollution: approximately 5,000 km National Agencies of the Centre of watercourses are completely denuded Fishing as a hobby is allowed for those of any fish. The fishing association (a who hold a permit, which can be bought; private organisation) is deeply interested that is, members of the fishing associa­ AUSTRIA ITALY in preserving fresh waters against pol­ MALTA tion. There are limits on the months Univ.-Prof. Dr. Franz WOLKINGER Dr ssa Elena MAMMONE Mr Joe SULTANA lution. There are intensive training Österreichische Akademie in which fishing is allowed, depending Ministère dell' Agricoltura Health Department courses for inspectors who ensure the Contributors der Wissenschaften Ufficio delle Relazioni internazionali Merchants Street on the type of waters (between May and monitoring of water quality and ascertain Institut für Umweltwissen­ 18, via XX Setternbre M - VALLETTA December in reservoirs, for example), schaften und Naturschutz I - 00187 ROMA sources and consequences of pollution. to this and on the species, number and mini­ Heinrichstraße 5/III Regional authorities, police and the A - 8010 GRAZ mum weight or length of the captured issue: THE NETHERLANDS courts are expected to be helpful in the LIECHTENSTEIN fish. Ing. Mario F. BROGGI M r D. A. HUITZING prevention and restriction of pollution BELGIUM Liecht. Gesellschaft Ministry of Agriculture and Fisheries According to the Nature Conservation accidents, which here number about Eaux et Forêts für Umweltschutz Auslandsreferat Chief Directorate for Nature Act, 14 species of fresh-water fish are 300 a year. 29-31, chaussée d'Ixelles Heiligkreuz 52 Conservation and Outdoor Recreation B-1050 BRUXELLES Postbus 20401 fully protected, including several species M. Paddy O’Toole FL - 9490 VADUZ It would be advisable to build more Minister for Fisheries and Forestry NL - 2500 EK THE HAGUE of lamprey, the Sterlett and the Danubian (small) reservoirs in suitable sites. They Leeson Lane salm on (Hucho hucho). IRL - Dublin 2 would also be, though not perfect, CYPRUS LUXEMBOURG NORWAY Nature Conservation Service M. Charles ZIMMER Mrs Irene SIGUENZA Only one, the last, is artificially bred replacements for wetlands that have M. Ignacio Claver Farias Ministry of Agriculture and Direction des Eaux et Forêts Ministry of the Environment Direccion General del Medio Ambiente and reintroduced to pollution-free flow­ been drained, or destroyed by the Natural Resources 34, avenue de la Porte-Neuve Myntgaten 2 Ministerio de Obras Publicas y Urbanisme ing waters. All the others, particularly expansion of our civilisation. J.K. Forest Department B.P. 411 P.O. Box 8013 Paseo de la Castellana 67 CY - NICOSIA L - LUXEMBOURG-VILLE N - OSLO 1 E - Madrid 3

Prof. Dr. Wilhelm Harder DENMARK PORTUGAL Universität Tübingen Miss Lotte BARFOD M. Rui FREIRE DE ANDRADE Lehrstuhl Zoophysiologie National Agency for the Présidente da Direcçâo Institut für Biologie III Protection of Nature, Liga para a Protecçào da Natureza Auf der Morgenstelle 28 Monuments and Sites Estrada do Calhariz de Benfica, No. 187 D - 7400 Tübingen 1 Ministry of the Environment P - 1500 LISBOA Fredningsstyrelsen Mr Nils-Arvid Nilsson 13 A m aliegade Institute of Freshwater Research DK - 1256 COPENHAGEN K SPAIN S - 170 11 Drottningolm M. Joaquin ROS VICENT Centro de Estudios de Ordenaciön Mr Derek Gren del Territorio y Medio Ambiente Thames Water FRANCE Ministerio de Obras Püblicas y New River Head M"= Isabelle RAYNAUD U rbanism o Rosebery Avenue Direction de la Protection de la Nature Paseo de la Castellana 63 GB - London ECIR 4TP Ministère de l'Environnement E - MADRID 3 14, boulevard du Général-Leclerc M™ Helga Inden F-92524 NEUILLY-SUR-SEINE Cédex SWEDEN Deutscher Naturschutzring e.V. Mrs Anne von HOFSTEN Bundesverband für Umweltschutz (DNR) Geschäftsstelle, Kälkuhlstr. 24 FEDERAL REPUBLIC National Swedish Environment 1. Salmo salar Protection Board D - 5300 Bonn 3 OF GERMANY 50-120 cm, Salmon D eutscher N aturschutzring e. V. P.O. Box 1302 2. Rhodeus sericeus amarus Dr. Anton Lelek Bundesverband für Umweltschutz S - 171 25 SOLNA 10 cm, Bitterling Forschungsinstitut Senckenberg Kalkuhlstraße 24 3. Cobitis taenia Senckenberganlage 25 P ostfach 32 02 10 D - 5300 BONN-OBERKASSEL 3 SWITZERLAND 7-10 cm, Loach D - 6000 Frankfurt 1 Dr Jürg ROHNER 4. Tinea tinea Ligue suisse 30-50 cm, Tench M. Henri Hoestlandt GREECE pour la protection de la nature 5. Anguilla anguilla 8, Contour de l'Eglise M. Byron ANTIPAS Wartenbergstraße 22 F - 59380 - Bergues 40-90 cm, Eel Secrétaire général Case postale 73 6. Salvelinus alpinus Société hellénique pour la CH - 4020 BÄLE Dr. Enrico Gelosi protection de la nature 25-40 cm, Charr Stabilimento Ittiogenico 9, rue Kydathineon 7. Silurus glanis di Roma, Regione Lazio GR - 10558 ATHENES TURKEY 1-2 m, Via della Stazione Tiburtina Mr Hasan ASMAZ 8. Leuciscus souffia I - Roma President of the Turkish Association 15 cm, ICELAND for the Conservation of Nature Mr. William Dickson Mr Gisli GISLASON and Natural Resources 9. Abramis brama National Swedish Environment Director Menekse sokak 29/4 40-60 cm, Bream Protection Board, Box 1302 Nature Conservation Council Kizilay 10. Gobio gobio S - 17125 - Solna Hverfisgötu 26 TR - ANKARA 15 cm, Gudgeon ISL - 101 REYKJAVIK M. B. B üttiker 11. Lampetra planeri UNITED KINGDOM 15 cm, Sand-piper Service des forêts et de la faune Conservation de la faune IRELAND Miss Shirley PENNY Chemin du Marquisat 1 Mr John McLOUGHLIN Chief Librarian CH - 1025 Saint Sulpice Department of Fisheries and Forestry Nature Conservancy Council Forest & Wildlife Service Great Britain Headquarters Drs. M. P. G rim m Leeson Lane Northminster House Head, Research Department IRL - DUBLIN 2 Northminster Road Organisatie ter Verbetering (Photo W. Lapinski) GB - PETERBOROUGH PE1 1UA van de Binnenvisserij Postbus 433 NL - 3430 AK Nieuwegein The illustrations on the back cover are taken from the poster “ Fish of Swiss Dr. J. Kleinert waters" published by WWF Switzerland, Slovak Society of Nature CH-8037 Ziirich, Panda magazine and Landscape Guardians Information concerning Naturopa,the European Information Centre tor Nature Conservation or the Council of Europe may be obtained from No. i/83 CS - 97602 Stare Hory the Centre or the National Agencies listed above Naturopa 47E - 1984