SOME ATTEMPTS TO IMPROVE THE HABITAT OF FISH, PARTICULARLY WITH THE USE OF NAUTEX
BY PAUL CAPDEVIELLE
General Secretary of the Federation of Les Landes
The vast lakes and ponds of the North Landes (nearly 25,000 acres), formerly very rich is pisciculture, have been the victims, in a few years, of rapid and catastrophic impoverishment, both of the fauna and flora. The reasons? Numerous causes have been suggested, some of which were fantastic.
The first serious studies by qualified technicians date back to 1960, when Mdme. Wurtz, senior research worker at the Central Station for Applied Hydrobiology, came to study the problem on the spot, at the request of the late former president, Mr. Lestage. Then, in 1962, it was the turn of Mr. Lamarque, an engineer from the Institut National de la Recherché agronomique (National Agronomic Research Institute) (I.N.R.A.) Continental Hydro biological Station of Biarritz.
This research revealed that the impoverishment of the ponds of Les Landes was due to a population explosion of the species bream. Its introduction dates back to 1946/1947 in the Aureilhan-Mimizan pond. Then, in 1957/58 it invaded the ponds of Parentis-Biscarrosse and Sanguinet-Cazaux-Biscarrosse, producing a state of unbalance in the fish populations (ratio of white fish to carnivores). The bream found a vacant ecological niche formed by the submerged plants and developed there in an amazing way. It caused the disappearance of 90% of the plants by consuming the vegetation direct (stomach contents) and in pulling it up in order to catch the oligochaeta worms among the roots. It also destroyed the fishes’ eggs and the very young fry (stomach contents).
This resulted in a thinning out and the disappearance of species competing for a similar diet (dace and tench) and the dispersion of the carnivorous species formerly frequenting the borders of the vegetation.
Alas, observations and solutions advocated by these two eminent scientists brought no reaction from the competent authorities, in spite of emphasis placed on the danger of this situation which must necessarily increase.
As from 1960, the local president Boutillon for Mimizan-Aureilhan, Labat for Parentis, Ducom for Biscarrose and their loyal collaborators took the happy initiative of large-scale stocking with fry of pike-perch, a species of great reproductive power; carnivorous but having no difficulty as to prey. This fish, which became perfectly acclimatised, was to reduce the stock of bream (1,600 metric tons in the three great ponds of North Landes).
In 1965 Mr. Capdevielle was appointed president of the A.P.P. of Sanguinet and he, in turn, attacked this disturbing problem. Rounding up with nets was organised on various occasions, with the very understanding agreement of the County Agricultural Board of Les Landes, requested by the federal president, Mr. Hontarrede, in order to destroy the bream, which has been declared to be a nuisance. Very considerable reductions were made in this way, both of the reproductive stock and the young specimens. Then, upon the initiative of the president of Biscarrosse, Mr. Ducom, a gully trap was set up at Navarosse, in the channel joining the ponds, which made it possible to capture thousands of fish of reproductive age and to destroy them during the spawning migration. Finally, nature came to the aid of the men of good will by infesting the bream with long, flat parasitic worms situated in the abdominal cavity, causing a compression of the vital organs, atrophied liver and a slow but fatal anaemia in the majority of the victims. We had an opportunity of observing a most enlightening fact: in the trap, we noted that when part of a worm emerged from the anal ampulla of certain bream, the others came in turn to pull at it with the mouth, little by little relieving their congener of its parasite.
The noxious fished were showing a very clear regression but the subaquatic plants, unfortunately, had already been destroyed.
Mr Capdevielle considered that the biological medium, which was also ruined, would not allow the renewal of these precious plants in water which was very acid since it came from the moorland, supplied by the rains trickling through the pine needles and over the heathland. Numerous samples were taken and analyses carried out, and the results compared with various records of earlier tests.
The following table, showing the partial results of analyses, confirms the rapid degradation:
April 1958 May 1963 Spring 1964
Calcium 18 mg 4.40 2.20
Magnesium 4 4.38 traces
pH 8 7 5.7
Dh 4 2.90 2.20
Mr Capdevielle, who considered that such a rapid and extreme degradation of the bictope could only be the consequence of a state of unbalance as great as that shown by the mineral salt content of the water, carried out many investigations, studies and enquiries. None of the reasons advanced up to that time, as to the cause or causes of the destruction, was, in his opinion, alone responsible for such disruption of such proportions. He therefore studied the relation between the impoverishment of the lakes and pools of Les Landes and the disappearance of numerous large herds of semi-wild cattle. Indeed, owing to the rapid growth of tourism and a great increase in road traffic, regulations had to be introduced in order to prevent the cattle from continuing to roam freely through the forest, causing accidents on the road and railways. The fact that it was not a profitable proposition prevented the owners from enclosing thousands of acres of pineland and they were obliged to get rid of their herds. Another reason for not keeping the cows was the fact that methods of forestry has been developed which involved the sowing of pine trees on fertiliser (slag), whereas previously the re-afforestation took place in the course of nature, in an irrational way; the cattle were detrimental to the development of the seedlings, grazing on the young pines, which were very advanced and forced but particularly tender and fragile.
The older members of the community affirm that there were almost 2,000 head of cattle on the shores of the lake of Sanguinet-Cazaux-Biscarrosse alone, at a time not very long past. These animals lived throughout the year in the open air, day and night in complete liberty, finding their essential nourishment on the shores of our pools (grasses, rushes, reeds, horsetails, young shoot of shrubs, etc.) Then, throughout the year, the cattle manured and urinated in the water, as well as keeping down vegetation which was not of great use in fish breeding except to provide shelter, although it is usually much too extensive. The reeds, by the amazing rapidity with which their roots spread, represent the difficulty of aquiculture. Thus, our ponds received a daily contribution of tons of rich, natural manure. It should be mentioned that since we have been making observations, hunters have reached similar conclusions regarding the reduction in the quantities of water fowl, which could no longer find the food which they had been in the habit of seeking in and around the cow patches. The undergrowth is a tangle, which is sometimes inextricable, of heaths, gorses and briars, whereas formerly the cattle were constantly trampling down the brush, making paths which were particularly followed by woodcocks, owing to their covering of grasses whose growth was aided by the excrement of the animals, the light and air. The marginal grassland, regularly cropped by cows, enabled migrating birds to stop to rest, as well as the fishes, and particularly the pike, to find excellent spawning grounds in the flood waters in early spring. Now these grasses, no longer grazed by the cattle, form, after withering, first a matted covering and then a soft, rotting mass seldom visited by the water fowl. Moreover, these borderlands, which have sometimes become stagnating bogs, bring about a somewhat accelerated rising of the ground and the rapid ageing of our ponds. Finally, the farms are being deserted by the young people and cultivation abandoned, so that there is no more manure or fertiliser which partially enriched the water trickling from very expansive slopes (about 7 times the area of the lake).
The population explosion of the bream species coincided, unfortunately, with the disappearance of the wild cattle. The hundreds of tons of bream relentlessly took the small amount of mineral salts remaining, particularly the calcium salts necessary for their bone formation. Finally, having over-cropped the sub-aquatic grasslands, they were obliged, in order to survive, to pull up the herbaceous root-stocks remaining, and feed on the oligochaeta worms hidden in the roots. Islets of grasses and roots could then be seen floating on the surface and blown onto the shores by the wind.
The bream, therefore, were not the determining cause but the aggravating and final factor in the process of piscatorial ruin of these marvellous jewels of nature which are the pools and lakes of Les Landes.
Moreover, at the same period, professional fishing was abandoned as it was no longer profitable. If fishing with large drag-nets caused undeniable depredations in relation to the size of the catches of carnivores, it had the great advantage of dredging the mud and decomposing organic matter, of cleansing the plants and recycling the mineral salts fixed by the mud colloids.
The situation was catastrophic, but how could it be remedied?
Mr Capdevielle followed the research carried out in England (1) by Frank Sawyer on the effects of chalk, with great interest, but not having the advantage of help from the public authorities, he decided, with the leaders of the A.P.P., to try fertilising test areas. Too soluble chalk would not be suitable, as the treatment of a lake of almost 15,000 acres according to volume could not be considered; entire trainloads of material would have been necessary. A slow-acting heavy material was needed in order to treat areas of the bed. Instead of chalk, 13 tons of industrial calcium carbonate was spread in the spring of 1965 over three shallow test areas near the shore (former spawning grounds) to enable the effects to be studied more easily.
The results were excellent:
restoration of the plants, from the rare clumps remaining;
the sub-aquatic sandy beaches, completely devoid of vegetation,
were covered with young plants and plankton;
fish gathered in large numbers in the treated areas, to the great
satisfaction of the fishermen;
analyses carried out in summer and autumn gave the following
results (in fertilised areas):
- Reported at length in this journal:
Calcium 4.8
Magnesium 2.5
pH 7.4
Dh 4
A very clear enrichment, therefore, of the biological medium.
These initial experiments attracted the attention of the Federal Guardians of Les Landes, then of Gironde, and finally of Mr Brunet, Chief Engineer of the Rural Council for Forestal and Hydrological Research, inspector general and technical adviser of the 6th piscicultural region, as well as of the Federal Governors of Les Landes and Gironde.
Mr. Brunet came to Sanguinet to study, in detail, the whole of the work carried out, as well as the possibilities of continuing and extending it. Greatly interested, he decided to approach the Fisheries Board in order to have this work financed, continued and controlled by I.N.R.A.
Mr. Hontarrède, Federal President of the A.P.P. of Les Landes, was kind enough to give very constructive advice regarding our projects and to encourage us to perservere.
The green light having been given by the Fisheries Board, it was necessary to find a supplier of chalk, and it was Mr Gagniard, manager of “Plaisirs de la Pêche”, remembering similar operations carried out on the streams of Normandy, who told Mr. Capdevielle of the Etablissements OMYA which were mining very special deposits of chalk in the Champagne area, marketed under the name of “Nautex”. This material is particularly fine, 1 gramme containing more than 20 thousand million particles, i.e., a developed surface area of about 2.6 square yards.
Nautex, of essentially coccolithic structure, causes:
flocculation of mud colloids;
de-composition of inert organic matter;
carbonic dissolution of these Cretaceous algae:
formation of a bicarbonate which can be assimilated by the
fauna and flora of the ponds;
a deposit on the water bed: calcium carbonate can be assimilated
by algae and crustaceans;
neutralisation of acid waters
proliferation of the benthic and planktonic population;
a reserve of calcium in the water;
improvement of the aquatic medium;
growth and multiplication of various bacteria allowing
autopurification.
Spring 1966
Arrival at Sanguinet of Mr. Lamarque, engineer, and Mr. Garaicoechea, diver, from the Continental Hydrobiological.
Exploration and survey of the beds treated in 1965;
exploration and survey of 5 areas to be treated away from
the shore in 1966, zones in which only a few sparse clumps
of vegetation, remains of former devastated areas of growth;
distribution of 20 tons of “Nautex” chalk from the Champagne
region and , a month later on the same places, 10 tons of slag.
August 1966
The technician from Biarritz dived again and observed the renewal of the areas of vegetation, certainly not yet homogeneous but large patches of fairly dense and very green growth. Thousands of young perch are always seen around these areas, feeding on the excellent benthos carpeting the water bed. It can be observed that the benthos and plankton are gradually reduced as the distance from the fertilised zones increases. New types of vegetation are listed.
Observations by fishermen:
Intentionally the test zones were chosen in shallow water (2½ to 3 yards deep) on the edges of deep hollows, in order to benefit from the maximum sunshine for effective photosynthesis. Without any wind and with the sun at an oblique angle, and the water being very clear in summer, the transparency was sufficient to enable all to observe the renewal of the plants and the abundant quantities of fish frequenting them. All the fishermen expressed their satisfaction at being able to catch fish again , by casting or dragging, from the beautiful vegetation which had been absent for years. In the late summer and autumn the fishermen made many good catches of pike and perch around the edges of the vegetation.
Encouraged by the first results of this experimental work under official control, all agreed that it should be continued and, if possible, extended.
Spring 1967
Eight zones treated, including three new areas;
20 metric tons of Nautex chalk from the Champagne region;
15 tons of slag;
plus, at the request of the producers of Périgord chalk, interested
in this work:
7 tons of crushed quicklime
90 to 93% quicklime;
2 to 5% calcium carbonate;
5 tons of calcareous mixed ameliorator
42 to 46% quicklime
23 to 25% carbonate of lime.
The technician from Biarritz, Mr. Garaïcoechea, made further dives, accompanied by Mr. Marty, before and after spreading operations.
Observations on the materials used:
a) Chalk from the Champagne region and slag confirm the excellent results
obtained in 1966.
b) Quicklime: although supplied in plastic sacks, this is inconvenient and even
dangerous to handle. The sacks are transported to the distribution areas by
ferry barge, and when waves pass over it, the quicklime, heating up in the
presence of moisture, bursts the sacks. Finally, at the time of the scattering,
the handlers, in spite of wearing rubber gloves and protective goggles,
experienced difficulty, particularly when there was a wind.
c) Mixed limestone ameliorator: better utilisation than in the case of the
quicklime; heavier material; a part which sank better, probably on
account of the calcium carbonate content, gave good results with regard to the vegetation.
It should be noted that these two latter materials caused less plankton production than the chalk.
Summer 1967
Areas of vegetation: The 5 zones treated in 1966 now show continuous, dense, homogenous, high and quite green vegetation extending over several acres (difficult to estimate precisely under the water):
Very considerable proliferation of benthos and plankton:
large quantities of fish;
new species of plants listed;
good floresencence;
extension of the vegetation from the shallows towards the depths.
The three new zones showing a distinct improvement offered the same
features as the 5 preceding areas at the time of the first distribution.
Mud: so far the unsilting action of the chalk noted in the streams has not, unfortunately, produced such spectacular effects in the lakes. Perhaps this is due to the absence of current, and it is also possible that the mud is of considerable thickness. It should be pointed out, however, that most of the experimental work has been carried out on sandy beds in shallow water. Two operations only were carried out on really muddy beds, but then at a depth of 4 metres, where reduced visibility hampered the observations of the divers.
However, two observations seem worthy of interest:
Distributions in shallows bordering hollows: a real un-silting was noted on the slope descending from the shallows to the depth.
Distribution on thick beds of mud: a renewal of the marginal vegetation was noted, particularly of nenuphars and sagittariae, as well as reduction in the thickness of the mud, which was emphasised in certain places where the chalk accidentally fell more thickly when being spread, forming small cones.
IMPORTANT, at least in our opinion:
For the first time we observed, in late spring, floating islets of dark grey seeds, which were carried onto the sandy beaches by the wind. Most of these seeds were buried in the sand by the surf, BUT in certain sheltered parts they were able to germinate and then, to our great surprise, we witnessed the development of small but very dense patches of potamogeton natans (floating pondweed) and followed its growth throughout the summer. Such an observation had never before been made here, at least to our knowledge. Is there a relationship fertiliser: production of seeds? That is the question, but it is certain that we saw improved florescence.
General observations:
In summer, fish swim over the whole extent of the lake, seeking, particularly, the deep hollows in the daytime when it is extremely hot, the water there being certainly cooler and probably more oxygenated, offering a possibility of revival.
In the autumn, winter and spring, for two years an attraction has been observed particularly of the fauna to the Sanguinet sector which had benefited from experimental work. The perch, which were formerly dwarfed, now reach weights of 2, 3 and even 4 lbs. The pike captured reach 24 lb. and occur more frequently. One fisherman, among others, living in Sanguinet, alone took 40 very fine pike this autumn. For two years we have observed a rarely seen intense proliferation of fry. It would seem that the dwarfed size of the perch noted in previous years did not arise through an over population of the species but through an insufficiency of the benthic or plankton food necessary for good formation and growth at an early age.
Spring 1968
Distribution of 20 tons of chalk from the Champagne area: “Nautex”;
10 tons of mixed limestone ameliorator at the request of the
Perigord producers;
15 tons of slag
over the 8 test zones previously treated.
Summer 1968
Dives by Mr. Garaicoechea, accompanied this year by Mr. Laurent, I.N.R.A., in charge of research at the Continental Hydrobiological Station of Biarritz, specialising in the study of interactions between mud and water.
Observations
Continued growth of vegetation, both in extent and density, as well as in variety of species, several new kinds being noted. Greater height of growth and a very distinct progress in the direction of the depths, where it was noted that plants were beginning to appear at a depth of 5 to 6 yards.
Mr. Laurent noted the presence of green patches of biological covering, of which he took samples and saw that these patches exactly covered the sheets of chalk.
Mr. Therezien at the Biarritz Station found in this biological covering:
Algae:
Chysophyceae: Dinobryon
Diatoma: Melosira
Eunotia
Surirella
Fragillaria
Gomphonema
Protista:
Dinoflagellata: Ceratium
Rotifera: Hexarthra
Observation of fishermen
For the first time, visiting fishermen caught one ton per month of roach in July and August.
Still in summer, the catches of carnivores, and particularly of pike were seen to be much more frequent, around the borders of the areas of renewed vegetation, than they had been in the preceding years.
CAZAUX 1968
The north-western part of our lake is managed, from the piscatorial point of view, by the Cazaux A.P.P., Federation of Gironde, which decided in 1968 to carry out the same work with fertiliser as at Sanguinet. The leaders of the A.P.P restricted their area of vegetation which existed in the past, which was extremely rich, well known and extensive, but where, unfortunately, not a single plant remained, as was confirmed by the divers from Biarritz before the distribution. The depth is about 7 to 8 yards and the thickness of the mud varies from 8 to 28 inches. Mr. Capdevielle, who was consulted, made reservations as he did not agree with the choice of working area, considering that for an initial renewal, the maximum depth of water, in order to benefit from effective photosynthesis, should not exceed 3 yards in that lake, and that, on the other hand, owing to the total absence of vegetation, growth and propagation could be started only with cuttings, layers, rhizomes, runners or seeds. In his opinion, it was necessary to seek a shallow area or a gentle slope from the bank, preferably where scanty vegetation remained, or otherwise, root-stocks should be planted in the lake bed and held in position, in order to form the centre of reproduction and spread.
The same materials as at Sanguinet, and in the same proportions, were distributed.
Sanguinet, Spring 1969
Distribution:
30 tons of “Nautex” chalk from Champagne;
15 tons of slag
still on the usual 8 experimental zones.
Dives were carried out by Mr. Garaicoechea and Mr. Laurent, who observed a height of vegetation never previously achieved, as in certain positions water milfoil was growing 2 yards high, providing rich nourishment. It was noted that new areas of vegetation were being formed around the borders of the experimental zones, outside of the distribution limits, and the extension of the growth is now continuing very distinctly outside of the treated zones. Confirmation of this progress in depth, slowly but surely, was obtained. A little vegetation was found 7 yards deep gaining on the mud.
Observation by fishermen:
In spite of a particularly hot and dry summer, which would formerly have kept the carnivores in the deep hollows, numerous pike were caught in July and August around the treated vegetation sheltering thousands of roach and perch fry. A good fisherman, for every two or three days’ fishing, caught one, two or three pikes ranging from 10 to 15 lbs., always in the same positions on the same stretches of vegetation. Is the water more oxygenated around the borders of these aquatic grasslands, for the applications to be rewarded so rapidly by fish whose size implied a solitary reign in an area? As for the catches of roach and tench, they are the most abundant, and many fishermen who had abandoned our lake return regularly, growing more numerous each year. The increase in size of the pike and pike-perch is remarkable, and pike of 19 lb. have been caught, a weight rarely reached even in the good old days of long ago.
Cazaux,1969
When, upon diving, the technicians from Biarritz found no trace of vegetation, this, unfortunately, confirmed what Mr. Capdevielle had foreseen. It is regrettable that in 1969 the distribution of fertiliser was not continued.
1970
If the authorities decide to preserve the experimental nature of the work at Sanguinet and continue the financial subsidies which they provide, the managers of the A.P.P. are, naturally, prepared to continue their efforts but can do so only on that condition.
From our observations and comparative tests, it would appear that by increasing the quantity of slag considerably, the efficacy of the work is greatly magnified. This is worth checking and specifying.
We are very happy to say that we believe that Cazaux intends taking up the work with fertiliser again.
The M.E.A.C. Company, which produces “Meaphos”, has asked the Sanguinet A.P.P. to be good enough to experiment with its product for a period of two years. This is a material which as a similar effect to slag but which effect should be shown to be accentuated. Composition:
18% phosphoric acid
56% calcium carbonate (lime)
1% magnesium
1% oligoelements
Particle size : 80% through sieve No. 28
(standard x 11505)
The future will show us the results obtainable from this material, as we have decided to devote one of our 8 experimental zones to work with Meaphos.
Extract from “Plaisirs de la Peche” 10 130 Feb. – Mar. 1970
Translator’s note: The precise title of the “A.P.P.” is unknown to the French Embassy but it is most likely that it is: “Association of Fishermen and Fish-breeders”.
Extract from “PLAISIRS DE LA PECHE”
No 131 – APRIL/MAY, 1970
By A. GAGNIARD
WHY, WHEN AND HOW TO USE NAUTEX
(One good treatment is better than two re-stockings)
It is now almost six years since I made known in France the surprising results of depositing powdered chalk, after having studied and verified the results obtained by Frank Sawyer in England.
It is now well known that, following work undertaken for the construction of a water supply, Sawyer, at first exasperated by what he took to be pollution, noticed the first symptoms of the beneficial effects of chalk. Since then, many stretches of water in France have been similarly treated. The “authorities”, who were at first reticent and sceptical, have gradually revised their position (better late than never), and a number of them are now wholehearted supporters of laying down deposits of chalk.
Furthermore, a number of reports on this very question were studied during the course of a scientific gathering in Biarritz last year. From the published account of these deliberations, it emerges that the beneficial action of chalk is now generally acknowledged, although, in my opinion, those present at the convention were far too cautious in their conclusions. Conversely, the diagrams which they included in their text are, in themselves, conclusive, as may be judged from this article.
Within the next ten years, chalk treatment will probably be used on a large scale on many major waterways, but, as we know, nothing happens overnight!
I take this opportunity to point out, once again, that there are different types of chalk. CaCO3 is sometimes found in crystalline form, in which case it has no effect whatever. The large deposits coccoliths, peculiar organisms, neither vegetable nor mineral, deposited over a period of thousands of years on the shores of an area which was then covered by salt water. This area included southern England, Champagne, southern Belgium, the Paris region and the Caux area.
The Omya Company, which owns the deposits in Champagne, showed interest in my tests from the very beginning and, in the light of the results, marketed, under the name of Nautex, the finest material that its quarries could produce.
The product is available in 25kg bags, the price per ton being in the region of 50 frs., exclusive of shipping costs.
WHY
I shall review briefly the double action of Nautex.
1. It promotes the rapid elimination of organic mud. I emphasise organic mud,
since a few users have met with failure in mud-clearing operations, due to confusing organic mud with silt. Organic mud is largely composed of decayed vegetable matter, which, during the slow process of decay, forms “mud-banks”. Silt, on the other hand, consists of fine mineral particles, often mixed with clay, on which chalk has no effect (silt, moreover, is not harmful). The process by which Nautex is able to eliminate the mud is not yet fully understood. Its action is undoubtedly complex, as has been shown in various theories, all of which are too scientific to be included in a popular article. Theories aside, with a few weeks of treatment, progressive elimination of the mud begins to take place. I have been able to establish, both in the course of my own tests and of treatments that I have been permitted to inspect, that the first effects become apparent 4 to 5 weeks after treatment.
During my first treatment, on the Iton, above Evreux, I achieved over an area of one kilometre, the complete elimination of mud layer 2 feet thick at the edges and 1 foot thick in the centre of the bed. This was achieved in the short space of six weeks. The owner of this particular stretch of water could scarcely believe his eyes.
2. The second effect of Nautex is perhaps less spectacular, but equally
interesting.
The elimination of the mud is accompanied by the appearance of plant life,
particularly the bright green moss, resembling absorbent cotton, which Sawyer considers to be an indication of very pure water. One example among many is that of the Charentonne, where, during the last few years, I have treated several areas which, even during the summer, were devoid of aquatic plant life. After the first application of Nautex, plant life began to reappear. Over one area treated last year, the vegetation became so prolific that only narrow “channels” of open water remained for the fly-fishermen.
One revealing incident occurred when an old farmer owning pasture land along the river said to me one day, half seriously, half jokingly, “Because of your chalk we’ll have to start clearing out the weeds again. We haven’t had to do that for tweny years!”.
It is, I think, unnecessary for me to point out that this plant life provides an abundant source of food for trout, all varieties of larvae, grubs, etc. One has only to examine any handful of grass to see that it is teaming with life. Naturally, as Sawyer emphasised, this abundant supply of choice food produces an improvement in the state of health of the trout, and there is evidence of spectacular rates of growth. A further example is that of the troutlets which, after being measured and ringed, were returned to the water at the end of May measuring 12 centimetres and were retrieved by the electric method at the beginning of September, measuring 18 to 19 centimetres.
WHEN?
According to my own experience and to the evidence that I have been able to gather, the most favourable period for treatment is from April to July. A number of technologists of the Eaux et Forets (Water and Forests Department) recommend treatment in the autumn. I beg to differ. Although this late period may be well suited to mud elimination, I prefer the spring, as the action of the sunlight at this time is more favourable to plant growth and to the re-establishment of the aquatic plant covering.
It is therefore preferable to treat in the spring, but after the flood period.
HOW?
I am often asked how large a quantity should be used. I would first point out that I have never observed the least harmful effect from the immersion of very large quantities.
Frank Sawyer, who is fortunate enough to have the chalk deposit only a few hundred yards from the river, and who also has free military labour and equipment at his disposal, has deposited hundreds of tons of powdered, or broken, chalk over the ten kilometres which he is treating. He has never noticed any adverse effect. Both he and I have observed, moreover, that trout favour the whitened, chalk-covered areas.
Another, very spectacular, occurrence is that during the first few weeks following a treatment, there is an invasion of thousands of small molluscs resembling winkles, but smaller. At the Chaise Dieu mill, for example, this invasion took the form of a procession extending over some tens of yards in length and 3 to 4 inches in width. I have observed the same phenomenon with Sawyer, during the filling of a number of large rearing basins hollowed out of the chalk which, in that region, is only slightly below the ground surface. Colonies of “winkles” made their way up the narrow channel which brought the water from the river.
1st year;
I recommend the following quantities as being desirable:
5 Tons per hectare (2.47 acres) of bottom area, e.g. a 1km stretch of river averaging 30 feet in width.
2nd year:
3 tons per hectare may be deposited if treatment is to be repeated in the third year (same quantity), if not, 5 tons once again.
I prefer the three-year treatment, repeated for two years, after a break of one year. Naturally, the method used will depend on the river and the circumstances. A river which, in autumn, collects large quantities of dead leaves must be treated with greater amounts than a river whose banks are bare of trees, (mud banks consist largely of successive layers of dead leaves which the current carries away and deposits at certain points).
Procedure:
The bags of Nautex should first be brought to the site by tractor and trailer. The ideal work-crew consists of 2 or 3 men carrying the bags and handing them to the 1 or 2 appliers working in the water.
It should be noted that, although a bag of Nautex weighs 25 kg on the bank, as soon as it is in the water, it becomes almost weightless and will in fact float (as filling is carried out by means of pneumatic machines, a certain amount of air remains in the bag).
The applier will, therefore, be able to handle the bag with ease and carry it to the spot where it is to be deposited. Since Nautex is extremely fine, it diffuses very easily in water.
It is, therefore, an advantage to place the bags at the head of the area to be treated and ideally, to have a raft situated at this point. The bags should then be placed on the bottom (side by side), where they will form a sort of boom across the current.
Placing the bags:
The applier should preferably work in waterproof clothing and should be equipped with a sturdy knife with a safety-catch to prevent it from closing on his fingers. He will then carry the bag to the required spot and perforate it about ten times over the top side (the bags are made of three layers of extra-strong paper). The applier should then kneel on the bag, if the depth of water will allow, or press it with his foot. The air will bubble out of the bag and, after 30 seconds, the bag will sink and the water will continue to enter. There is nothing more to be done for the moment.
If one is not fortunate enough to have a raft at the head of the area, or if the force of the current against the raft is too great, one can either only partially block the river-bed, or construct two or three lines of bags parallel with the river bank.
The same procedure may be followed if the water is too deep.
If there is rough water, a relatively calm back-current should be chosen in which to place the bags.
One can count on one group of bags being sufficient for 500 to 600 yards of river, where the mud is shallow, or on 200 to 300 yards where it is fairly thick.
Large, localised mud-banks must be treated separately. A number of bags should then be placed at the top of the mud-bank, unless it is joined to the river-bank. If necessary, the bags may be placed in shallow holes dug for this purpose in the mud. If the mud-bank is connected to the river-bank, on the inner curve of a bend, for example, the bags should be deposited against the edge in one, or a number, of rows.
Finally:
A few hours later, or the following day, the top of each bag should be slit with the knife and remover. This will leave a sort of paper tub containing 25kg of chalk – paste.
This paste should be stirred gently each day if possible, or once a week. This can be done with a stick, a rake, or even with one’s foot.
A white cloud will be formed which will gradually be diluted in the current. The fine particles will gradually settle, and examination under a magnifying-glass will show that every stone, every branch, or every mud-bank has, after a few days, acquired a fine coating of Nautex.
To achieve a good distribution, it is preferable not to proceed too quickly. My advice is to dilute little and often. It is quite permissible to spend 15 days, 1 month, or even two months diluting 5 tons per kilometre.
It should be noted that, if the chalk is not “stirred”, it will remain in the same position. The current, except in the event of a flood, will have no significant effect on the paste. “Stirring” should preferably be carried out in the evening, in order to avoid inconvenience to anyone fishing downstream. If this work is carried out as I have indicated, the white cloud should be visible for not more than 300, or 400 metres, and the visibility decreases as it is carried further from the starting point. I have often observed that trout continued to feed while “stirring” was taking place 200, or 300 metres upstream.
I think I have given all the essential information and details of procedure needed to achieve the maximum effectiveness from a Nautex treatment. If I have stressed the name “Nautex”, it is simply because I have been aware, from time to time, of offers of chalk originating from small, local quarries. These chalks can offer no guarantee of effectiveness. On several occasions, samples of marl have been sent to me as chalk. This material, which is excellent in agriculture, generally contains 25%, or 30% CaCO3 mixed with clay.
The effect may be negligible, or even harmful, as the clay may consolidate the mud.
Nautex contain 98.3% CaCO3. Its effectiveness is guaranteed.
I shall, of course, be happy to assist anyone requiring further information, or wishing to quote a specific case
A.G.
Captions:
Photograph (page 53) – This is a Nautex coccolith, enlarged 6,600 times under an electron microscope. Neither vegetable, nor mineral.
Diagram (page 55) – Cross-sections of the Levriere (east and west arms) at 10 month intervals
Compact, stick mud. (left)
Very smooth, sloping, rounded edges. (right)
Before chalk treatment. End of October 1968
And 10 months later – Early September 1969
Softer mud. (lower left)
Sheer, jagged, granular sides. (lower right)
Bottom wholly, or partially freed from mud. (bottom)
Thicker cover. Chalk-stones (bottom)
A TALE OF CHALK
A. Gagnaird
Translated from “La Peche”, No 163 Sept – Oct 1975.
It was in August or September 1964 that my friend, Raymond Rocher, staying with me whilst travelling through Normandy, told me of his work and of his conversations on the same subject with his friend Frank Sawyer, who had had several articles printed in the English magazine “Trout and Salmon”.
Very interested, I asked Rocher to ask Frank Sawyers’ permission to translate these articles and have them published in “Plaisirs de la Peche”. Frank Sawyer agreed, and they were printed in the issues dated December 1964 and February 1965.
In the meantime I had contacted the owners of the Omya society, proprietors of the Champagne chalk quarries, who were interested in Frank Sawyers’ findings, and who put at my disposal some tons of powdered chalk, which allowed me to make some experiments in Normandy. The first treatments were made on a stretch of the L’Iton river, leased by my friend Caldayron from the Bernay Society, and they confirmed in every way Sawyers’ findings. For this reason I published a complete account of my work, together with the findings of some of my friends on their river beats, in the February 1966 issue of “Plaisirs de la Peche”. I think that it is useful to reproduce the main points of that article here, because chalk is so effective!
First of all it has been found that 95% – 98% Limestone (Carbonate of Lime) is the best material to use. This grade of powdered chalk is sold by the Champagne quarries, but that first used in 1965 was supplied by the Omya Society, who have been very helpful as far as price and delivery are concerned. One could also use marl, or clay chalk, but the analysis is only 35% – 40% limestone, and therefore double the amount is required. The marl, or clay chalk, does contain a high percentage of clay, or potters earth, and this will slow down the elimination of sludge/slime, which is one of the first objects of this treatment.
The powdered chalk is delivered in paper sacks, each weighing 50 kilos, similar to those bags used for cement. They can be stored for several months without coming to any harm, as long as they are protected from rain. These paper bags are now being replaced by plastic bags of 25 kilos, which are much more manageable.
Now let us consider the best time to apply this chalk. Frank Sawyer suggests that chalk can be applied at any time of the year. I prefer the spring, before the start of the fishing season, or even after the season has ended. It must be applied in small quantities, in order not to disturb the water to any degree, and so that fishermen will not be inconvenienced for any length of time. One could also choose a time when floods are unlikely to occur.
The quantity of chalk applied is important, and a massive dose is vital in the first year. I would advise the use of 5 tons per kilometre of river, assuming the average width to be 8 or 10 metres. The depth of the river is not important because it is the bed of the river that has to be treated.
The method of treating the river with chalk should be as follows. The sacks of chalk will be brought to the river bank at a pre-determined spot, and we will see later how to find the best site. It will be necessary to work in the water, so waders or rubber trousers will be needed. A balanced team would consist of 3 or 4 men on the bank of the river, feeding the material to 2 men working in the river. Each sack should be placed flat in the water in the required position. Here it will float owing to the air trapped in the bag by the chalk, an interesting and useful peculiarity which reduces the apparent weight to almost nothing and allows one to manoeuvre the sack into the desired position. In one day on the L’Iton I was able to place 100 sacks, about 5 tons, in about 3 hours, without tiring myself, with only two men on the bank feeding the bags to me.
Once in the water the sacks are manoeuvred, semi-submerged, to the spot where they are to be sunk. A strong knife is then used to make 5 or 6 slashes in the bag, whereupon it slowly sinks to the bottom, taking an hour or so to replace all the air trapped in the powder with water. At the end of this time you have a sack of chalk paste. Again with the knife you cut away the whole upper area of the bag, so that you then have a basin of chalk paste sitting on the bottom of the river. If you leave this basin of paste untouched it will not move, dilute or solidify, so you have to stir it very gently with a stick or a rake, or even use your feet to move it. You will then get a heavy cloud of chalk forming which will spread across the bed of the river a drift down stream.
I would advise you not to distribute the chalk too quickly. It is best to “work” the chalk a little each day over a period of 15 days, and thus a get a steady distribution of chalk on the bottom of the river which inconveniences nobody.
When placing the sacks allow for the fact that you are looking for a slow, steady and uniform distribution of chalk on the river bed, and so when choosing a site bear in mind the following facts. You want a place in the river where the water is slack, so that a barrier of bags can be made across the stream without interrupting the flow to any degree. Whirlpools, weirs, waterfalls and eddies caused by rocks can be useful to distribute the chalk, but they have to be carefully used. Sacks can be placed on the edges of such places to take advantage of certain currents, and so get better distribution.
One starts, of course, by placing the sacks upstream of the area to be treated, however slowly the chalk is released from the bags quite a lot is bound to flow downstream for some distance. So a second site for placing the bags should be some way away from the first site. For this reason it is also as well to choose a time when the water level is not too high and the flow is, within reason, at a minimum. In certain circumstances it may be necessary to create calm water for the placing of the sacks of chalk, by making a partial barrage with sticks and timber.
The application of 5 tons, or 100 sacks, for one kilometre of river should be made as follows:-
40 sacks for the first 50 metres.
20 sacks for the next 200 metres.
40 sacks along the banks, roughly in the centre of the distance to
be covered.
It is a good idea to keep about 10 sacks in reserve, for use a month or two later on any part of the river bed that has not been covered in the main application. This way of applying the chalk is valuable for three reasons, de-sludging, encouragement and good weed growth, and to achieve profusion of small fauna.
On several stretches of river, in 1965, we were looking before anything else for the elimination of sludge from the bed of sludge, and sometimes directly on them, and we found that it was 4 to 6 weeks before results were apparent, especially when the bed of the river was very dirty. After several weeks we found patches clearing, and cleaning continued until the bed of the river looked as if a vacuum cleaner had been over it. Later still we noticed little tufts of weed starting to grow on the bare river bed, first where the water was shallow and light encouraged this growth.
It is only at the end of several months that the attentive observer will see a complete change in the river. If one has taken the trouble to make notes of the condition of the river before the treatment began ? will be even more aware of the changes.
On the River L’Iton, for example, on the distance of one kilometre treated, the width is 20 metres, and the average depth at the centre of the river is one metre. Before treatment there was abundant vegetation , but very little larvae, and an almost complete absence of water shrimps. Under the stones where one could link them over mud or the weed there were a few caddis. The river bed was almost 90% mud, 50 cm deep at the edges and 20-30 cm thick in the centre. The trout were thin bodied and had large heads. This stretch of river was treated with 5 tons of chalk over the first 400 metres. First results were noticed after about 4 weeks, when a large area of gravel appeared. At the end of 6 weeks the sludge had gone completely over a distance of 800 metres. During the summer a large increase of many kinds of larvae in the weeds were noted. During June one was able to see that the trout were in much better condition than they had ever been in before. By September, the end of the fishing season, the trout really were in good condition and full of fight. During the whole month one heard almost every day of fish feeding ? on nymph. There were tens of thousands of grey coloured nymphs on the leaves of the reed of 3.4 mm in length.
Another treatment of 5 tons was made on the second half of the river at the end of July. The obvious effects were less rapid than they were in the spring treatment. Another treatment was to be made in the following spring.
On another river, the Charentonne, the width was 10-12 metres, and the average depth 70 cm, and the length of river treated was 4 kilometres. Before treatment weed was almost non-existent, and under the stones a ? few nymphs, and a few caddis in the weed. The fish were in fairly good condition, but they had only just been put into the water ready for the fishing season.
At first treatment of 5 tons was made in the spring. 5 Sacks at a time were emptied at various places, the dilution was immediate and total. The river was milky for several kilometres, and 20 kilometres downstream six hours later a light milkieness was still noticeable. In spite of the bad conditions, 4 or 5 weeks later areas were seen where the gravel was clean. Shortly after better weed growth was noticed, bright green in colour, where the sacks had been emptied.
A further treatment of 3 tons was made just before the end of the season, and 4 weeks later results were apparent. As in the L’Iton, the bed of the river appeared to have been vacuumed, the weed multiplied rapidly, and in October, on calm days, the activities of fish feeding heavily was noticeable. Records allowed us to note a big increase in larvae and shrimps. At the time of writing many more spawning areas are appearing. Another treatment will be given to this area next spring.
It would be repetitive to relate the results of other treatments given to other rivers in 1965, the effects were all more or less the same. Nevertheless it was noted on several sections of tributaries of the Levriere river that few trout were found that section was full of sludge. After being treated with chalk the sludge went, the trout came back and remained.
I cannot recommend too strongly that my readers should try this treatment, I am sure that they will benefit by the experience, but I would point out that the treatment must be carried out for at least three years in succession. I would be interested to hear from anyone who has used this method of cleaning a river.
At this time I had a meeting with Richard Vibert, when I asked him his opinion of this treatment with chalk. His reply was most encouraging, and amongst other things he told me that it was only the shortage of men that prevented him from trying it out in the Pays Basques.
Some months later he had the opportunity of following the results of treatment carried out by one of his friends in the region of St Jean le Vieux, and they were the same as described elsewhere.
It was at about the same time, at the instigation of Mr Costaz, Director of Agricultural Department of L’Eure, who had followed my different trials, a meeting was held at Evreux to discuss what was called at the time the “Chalk Affair”. An amusing point to make was that I was not invited to attend! But I must mention that Mr Costaz wrote an article in the journal Eure – Eclaire, 25th February 1966, in which he mentioned the principal points in my article in Plaiser de la Peche, and added that the simplicity of this method and the low cost made him hope that the experiment would be repeated extensively. All that remains is to discover, perhaps unkindly, the sensational results!
In 1966 – 1967 many treatments were made in France, mostly in Haute and Basse – Normandy. If Mr Costaz and the authorities of the L’Eure still favour the treatment, which still show positive results, it was not so in the Seine – Maritime and in some other counties where the authorities wanted to forbid the chalk treatment.
In 1975, about ten years after my first experiment, one can say that the specialists in hydro-biology are willing to admit that there is something very interesting in these experiments, and I leave the reader to draw his own conclusions.
Mr F. Sawyer
Court Farm Hall
Netheravon
Wilts
19th April 1966
Dear Mr Sawyer
I should like to take this opportunity of thanking you for the very pleasant reception which you gave me when I visited you last week, and I can only hope that this initial discussion may have been of some assistance.
Since returning to London I have been doing a little homework which has elicited some information that I think will be of use to you. I am currently making a précis of this and will forward it to you during the course of the next few days. In the meantime, the following abstract may be of interest to you:-
“Considerable quantities of the solid carbonates of lime (calcium) and magnesium are present in the soil in chalky and limestone districts, but they are relatively insoluble in pure water. When carbon dioxide is present, however, they become changed to soluble bicarbonates thus providing a reservoir of carbon dioxide for the plant life. When calcium bicarbonate by itself, or along with calcium sulphate, is present in any quantity we call the water hard or alkaline. Often a hard chalky coating can be found on some plants growing in hard waters. This results from a withdrawal of carbon dioxide from the soluble bicarbonates in water causing precipitation of the carbonate on the plants. Such hard waters suit some creatures but not others. Thus, fresh water sponges cannot stand excessively hard water, whereas many snails whose shells are, of course, largely made up of chalk, thrive best in it. As a general rule waters fairly rich in calcium carbonate and therefore slightly alkaline or hard, are productive of more plant and animal life than are soft calcium deficient waters such as moor land bogs and the like.
Regarding snails, the shell which is a characteristic feature of a gastropod, consists largely of calcium carbonate or “chalk”, and is actually made up of three layers each differing from the others in composition. These may be seen by carefully examining an empty shell. The thin outer skin-like layer serves as a protection to the shell particularly in the case of the aquatic species where it guards against the action of organic acids in the water. This is composed of almost pure conchyolin which is a substance somewhat similar to the chitin of insects. In older shells much of this skin may have been rubbed off to reveal the middle layer which forms the major part, and consists largely of calcium carbonate crystals arranged perpendicular to the surface of the shell. The inner lining of nacre or mother-of-pearl is also made up of calcium carbonate, but in this case the crystals are lying parallel to the shell’s surface. The large amount of calcium which enters into the composition of the shells of molluscs makes it necessary for them to live in situations where there is an adequate supply of calcium salts, and with decreasing amounts of calcium in the water the number of snails becomes progressively fewer. Quite apart from the needs of shell making, calcium is important to fresh water molluscs in other ways. Firstly, the production of higher plants and algae. Secondly, lime has the property of agglutinating particles of clay. Such particles in suspension in the water are thus precipitated and the water is kept from becoming turbid, a condition of importance to those molluscs that breathe by means of gills.”
I shall get in touch with you once again when I am able to fix a firm date to deliver some samples of P.C.C. slurry. Since speaking to you I find that I have to attend a conference from 15th to 19th May, and it therefore looks like Monday, 23rd May will be the earliest opportunity I shall have. Perhaps you could let me know if this or some other date during the week would be suitable.
Yours sincerely
J D Hunter
Translation of Technical Bulletin:- 224/366 – Omya S.A. Paris
Action of Calcium Carbonate on Fish Life
Calcium carbonate acts:-
- on the aqueous medium
- on the flora
- on the aquatic fauna
On the aqueous medium by dissolution or
- By dissoluition – in spite of its low solubility, chalk neutralises acid waters and turns the pH of the rivers alkali.
- it coagulates colloids
- it favours the action of bacteria, by self purification
of the rivers
By deposition – it covers the river bed with a protective layer,
particularly effective in streams charged with organic
matter of agricultural or urban origin.
- covers the mud
- participates in the fundamental equilibrium in pond
life
Ca CO3 ÷ H2O + CO2 = Ca (HCO3) 2
in which appears the very soluble calcium bicarbonate easily assimilated by the plants.
On the flora
- natural chalk is the “typical” fertiliser of aquatic
- media, feeding all plants with calcium.
- it is the ideal growth source for algae and aquatic vegetation
such as cress, moss, “callitriches” and “characees”
- it favours the oxygenation of the waters (chlorophyll
assimilation)
On the fauna
The proliferation of algae and plankton brings about a very notable growth of micro-organisms, insects, larvae and crustaceans, of which the trouts are the most delicious.
In addition, the improvements obtained by this treatment, such as the provision of a healthy and abundant food, the increase in dissolved oxygen etc., one has observed that the temporary turbidity of the treated waters has no deleterious effect on the spawning of the trout, on the young fish, or even on the feeding of the fish in general.
Method of Operation
Raw Material
Calcium enters into all vital phenomena but its action is dependent upon its structure.
Thus calcium oxide, sometimes used for fish cultivating purposes, presents many dangers to the aquatic world, if the dosage used and its method of distribution are not vigorously controlled.
A very fine raw material is required to favour both the solution and the dispersion of the particles of calcium carbonate over the whole extent of the river bed.
The use of calcareous marl – the only type of marl which could be used for this application – is not recommended, because its structure and its low calcium content limit the action of the treatment. Besides, by adding still more mud, it would have the opposite effect to that aimed at.
In order to avoid unnecessary handling it is necessary that the specific mass of these particles should be rather low. The current is sufficient to distribute over a great distance.
Desirous of providing an effective treatment, Omya have studied this problem and can offer a quality of natural chalk of very fine particle size, and particularly pure, since it contains 98.7% calcium carbonate.
Of amorphous structure, thus easily assimilated, the natural chalk is formed from planktons and coccolithic aquatic organisms deposited during the secondary era. This marine origin makes it particularly suitable for discharge and confers to it an exceptional specific surface – each gram of chalk has a surface area of 25,000 cm². In addition it has a great case of dispersion since each gram contains 88 million particles.
Quantity
In the review “Truite, Ombre et Saumon” of the 4th Quarter 1965, Gagniard makes the following recommendations in his article:-
“Results of one year of chalk” :-
First, do not pour the chalk into the stream, but place the bags flat in the water in selected spots (dead or calm edges, down stream of rocks etc.)
- remove the outer layer of the submerged bags.
- Periodically stir the paste formed where the bags
have been deposited, this method provides a good
distribution and the best action spread over time.
This depends very much on the type of river bed, but Gagniard recommends 5 tons of natural chalk per kilometre (width of river 10 -12 metres)
The chalk settles:
40% in the first 50 metres
20% in the next 200 metres
40% at 500 metres
Such a settlement on an annual basis causes little turbidity.
Duration of treatment
It is recommend that the treatment should be carried out in the Spring, and to avoid the seasons of high water and floods.
Results
The action of the chalk on the aquatic life is fairly quick, on condition that the intensive treatment is carried out to cover an extensive surface.
JDH/MDB
13th May 1966
