Part III

to trout ova. Therefore it is apparent, that by protecting the eggs, we are doing a great deal. But we are doing more, for the artificial beds shelter the " alevins " for awhile, and after they drop down the little artificial stream they are still shielded from the bulk of the dangers enumerated, especially from the depredations of trout and other fishes. The streamlet used as a hatching bed should be so constructed that no outsider of the trout family can by any possibility get into it. Eggs, before hatching, have no power of protecting themselves, or of getting out of the way of danger. As soon as the embryo is out, it at once possesses some power of self-protection. It has a pair of well-developed eyes, and knows how to use them, and immediately that wonderful power called instinct causes it to seek a hiding place. So strong is this desire to hide, that if the little creatures cannot find any other place they will hide under each other, and in doing this they gather together in dense masses, reminding one of a swarm of bees. Californian baskets, which are simply wire cages in which eggs are piled one above another, do not suit the eggs of our British Salmonithz, It is true that by using them a large number of eggs can be hatched in a small space, but the result is undoubt- edly a partial suffocation of the embryos, and a general weakening of the young fish, They may do well in America, but what will suit the fish of one country often may not agree with the fish of A another. lower prevailing temperature is, no doubt, to some 1 82 How to obtain it. extent, more favourable for the use of such an apparatus, than the comparatively higher one in this country. But whatever be the am reason, I satisfied of one thing, and that is, that the grille system is the one of all others for successful work in Britain! It gives the eggs plenty of room, and removes all danger of suffoca- tion where a good current is run over them. The carbonic acid given off by the egg is at once carried off, and the absorption of the oxygen from the water is unhindered. In Germany, perforated glazed pottery is used extensively for hatching ova upon, and, with the water welling up through the perforations, it does very good work. It has its objections, however, those of cost and liability to breakage being not the A least. broken tube in a grille is easily repaired, or replaced, but not so with a piece of pottery. To repair a broken tube, all that is necessary is to insert a piece of charred wood, cut to the proper size, into one of the broken pieces, so that half of it remains projecting. Then slip the other portion of the tube over this projecting piece, and the tube is again ready for use. Grilles can be made of ordinary window glass cut into strips, and fitted into a cogged or notched wooden frame. The cost of making the frames, seeing that every cog has to be separately charred, is considerable, and it is on this account chiefly that they have fallen into disuse. A few still remain in operation in my own hatcheries, and considering only the hatching of the ova they do quite as well, if not better, than the more modern arrangement of glass tubes or rods. It has been suggested that the rough edges of the glass will cause injury to the ova, but this is by no means the case. I have hatched many millions of ova most successfully on these grilles, and have found them to work very well indeed. The advantages of the more modern invention are that they are a little easier to make, and the glasses are not so apt to fall out, and those who have to use them prefer them to the old style. One of the chief things to be avoided in a hatchery is the overcrowding of the eggs. It should never be permitted under any circumstances. I have tried a number of experiments with ova, with a view to economising space when necessary, and many years ago, before baskets and cages were thought of, I invented a hatching-box, in which several grilles can be placed one over the How to obtain it. 183 other. As soon as the eggs will bear moving, the grilles may be lifted from the hatching-boxes and placed in a compact storagebox, the working of which is explained by the accompanying woodcut. This box is divided into compartments, each holdingfour grilles, or, if the grilles be placed directlv on each other, six of them may occupy the same space. The compartments, it will be seen, are so arranged that the water enters each at the bottom, rises up through the grilles, and keeps the ova in sound healthy condition. This box I designed in the early days of fish culture, and have since used it successfully both for ova and fish. It was honoured by a medal at the Yorkshire Exhibition held at Leeds in 1875, where the design was applied to a series of aquarium tanks, for which purpose it answers admirably. I had it in use in 1870, and about the same time it was patented in America. Fig. 20. CHAPTER IX. PACKING AND UNPACKING THE EGGS. Ova to the Antipodes The tropics Various methods Modus operandi at the Solway Fishery Selecting and preparing the moss Its cultivation Woven fabric Best time to pack Ova hatch rapidly on unpacking Long voyages Unpacking Washing off the moss Fully eyed eggs. T I is now pretty well known that trout and other ova can be packed and sent with success, not only to any part of the British Isles, but to any portion of the world that may be desired. If has- been so sent, and the waters of the Antipodes have been most successfully stocked, as we have seen, by means of ova sent out first from this country. Attempts are being made to stock some of the hill streams of the tropics. Up on the mountains, where the atmosphere is cool and the cold snow water comes down the streams, trout should succeed well, and it is by means of ova that they must be introduced. The use of ova, too, is destined to play a very important part in the stocking of our waters at home, and therefore the packing of the delicate little morsels becomes a matter of very great importance. I find it is rather a common notion that trout eggs can be packed up by anyone at a moment's notice, and with very A little trouble. greater mistake could not be. The successful packing of ova is an art that has to be learned by careful training and experience. I have, in the course of my life, received a great many consignments of ova from a great many different people, both at home and abroad. When I say that no two senders have packed their eggs exactly in the same way, it will be apparent that there is a great diversity of idea on the subject. I have seen eggs How to obtain it. 185 packed in mosses of many descriptions, in cotton wadding, in flannel, in water, in gravel, in muslin, and many other substances. The work is by no means difficult, and when the principle is once understood and the requirements of ova have been sufficiently studied, a dexterous hand will soon become expert at their manipulation in large quantities. When a quarter of a million of eggs have to be packed in a couple of hours a system is required in order to carry on the work. The eggs are packed in trays which are made of wood with a bottom of perforated zinc. One worker places a sheet of felted moss at the bottom of each tray, and upon it a piece of swansdown or fine netting. Another takes the eggs off the grilles in the hatchery, and carries them into the packing room, where they are deposited in bowls, on a bench near the packers. The eggs are so easily counted on the grilles that the exact number in the bowls is known. They are all measured as they are put into the trays, however, and the measure being ascertained by counting to hold a certain number, checks the count of the ova on the grilles, and prevents the possibility of any mistake. The eggs are transferred from the measure to the fabric in the packing trays, and by a stroke of the hand gently spread with the help of a heron's feather. The tray is then handed to an expert, who picks out any blind or white egg, or puny embryo, should such be discovered to have been overlooked when the eggs were picked over on the grille in the hatching box. This can only be done in the daylight, as it is impossible to detect the difference when eggs are packed during the dark hours. The layer is then covered with another piece of fabric, over which is placed a second layer of felted moss, which in its turn receives a sheet of fabric, and a layer of eggs. Three layers of ova, four or five sheets of felted moss and six egg cloths form the contents of each tray, and the trays are piled one on the top of each other as required, up to the number of eight, and these are placed in an inside case contained in a box of sawdust. They are usually lifted out of this case by means' of a flannel band, which is passed underneath them in packing. In this way a large number of eggs may be packed in a short time by either men or women. They should never be touched by the hand. 1 86 How to obtain it. There are other ways of manipulating them, and I suppose that at every hatchery the plan will vary somewhat, but, after trying many other methods, I have found the one described to be the best and simplest. Two thousand eggs are placed on a layer very often, and in this way forty thousand eggs occupy the same space as a much smaller number would, thus saving labour and freight to ourselves, and a lot of trouble and half freight on empties to the receivers. I have carefully tried many experiments with ova in order to ascertain the necessary conditions for conveying with safety the largest number of eggs in a given space of reasonable dimensions. A great deal more depends upon the packing, the temperature, the supply of oxygen, and the preparation of the moss than most people suppose. To begin with, then, let us consider the moss itself. I tried a good many kinds of moss, and there are several kinds that under proper cultivation may readily be made to answer all the purposes required. But to gather mosses indiscriminately, taking any likely-looking stuff that comes to hand first, is not the way to promote the safety of the eggs. Many mosses grown in woods are unsuitable, from the fact of their being so much of foreign admixture among them in the shape of minute bits of stick, rotten leaves, roots (some of which may be highly poisonous), and other matter. Those found in very wet places often grow so luxuriantly that the lower parts decay, and are on that account not good for packing ova. I have found some sphagnum beds to be full of animal life, and others again containing Saprole^nia^ or fish fungus. In a large establishment, where everything has to be systematized, the moss is felted, and as only some kinds can be readily manufactured into felts, the moss question becomes a very serious one. So much is used at the Solway Fishery that it has become needful to grow it, and this is an excellent way over the difficulty, as it can be gathered clean and fresh, there being only one year's growth to deal with. After it is gathered the ground is replanted, and although no manure is applied, and the same crop is taken off it each season, yet after several years the soil seems to be in no way impoverished. The only change that has been observed is that each succeeding season a finer and richer crop of moss is produced. How to obtain it. 187 It should be well adapted for packing embryo trout, for it has been largely used for packing human infants by the Lapland women, who wrap their children in it. When well dried it is found to provide an exceedingly good protection against cold. The moss is gathered and carefully kept in a cool, damp place, where it undergoes the felting process, which is very simple. A number of presses are filled with layers of moss and sheets of perforated zinc alternately, and after remaining all night, the moss is taken out beautifully felted next morning, and so a fresh supply is continually being produced. It is not by any means necessary to felt the moss ; indeed, so far as it and the eggs are concerned, it answers the purpose just as well without being felted, but for packing large quantities of ova it is an absolute necessity to have everything expeditiously done, considering the price at which trout eggs are put upon the market. The fabric which is used between the moss and the eggs should first be well washed, to cleanse it from starch or any other impurities. I once received a lot of ova which may be said to have been packed in window curtains and starch. The sender had cut up an old curtain, and used the pieces stiff with starch for packing the ova, with the result that on unpacking here they came out a conglomerated mass of eggs and starch. The eggs were covered with the slimy stuff, and had to be well washed. I have seen more than one case of this kind. Now, although starch is considered sufficiently wholesome to give in large quan- tities to human infants, it is decidedly bad for trout, and its use is to be avoided. Had the journey been a long one the eggs might have suffered materially, and in any case there would be a great risk of their being attacked by that most dreaded pest of the fish culturist, Saprolegnia (fungus). It would not attack them probably until they were in the hatching boxes, as it does not grow readily in air, too much oxygen being fatal to it. Hence the necessity for carefully washing the eggs before laying them down. It should always be done. Old window curtains, after being well washed, make excellent packing material for trout ova, but a variety of fabrics may be used. The great point to be observed is cleanliness. Eggs may be packed as soon as the eye spots begin to show i88 How to obtain it. black, and, with the rapid steam communication which we have nowadays, they may be safely started on very long journeys at this stage. They are about half incubated, and, when packed in moss and iced, they will not hatch so soon as they would have done in the trays in the hatchery. The low temperature at which they are kept during ocean voyages slightly retards the develop- ment of the embryos. When packing eggs for export a few are invariably retained, packed in moss exactly like those exported, and kept at a low temperature, and these usually remain unhatched for fourteen days or so after the date of arrival of the consignment sent abroad. On being unpacked and placed in a hatching box they generally hatch very soon. I have received accounts of ova successfully sent to the Colonies, which have, on unpacking and being placed in the hatching boxes,, hatched in a few hours. On one occasion a lot which were sent to Natal hatched off in a few minutes, the temperature of the water being over 60 F. This was a very natural result after being taken from their well-iced packing case. The temperature of the water was first lowered by means of ice, and then allowed to rise gradually. Ova can now be sent very successfully to any part of the world. It is not to be supposed that no loss takes place on these consignments. Sometimes they travel beautifully, and, with the well-studied system of packing that is now adopted, there is every chance of this, provided they are properly attended to during the voyage out. For long voyages the eggs are packed in a very similar manner to the one adopted for home packing, though a few extra precautions are necessary. An air space is left at the bottom of the packing case, and the perforated zinc bottoms of the trays are all double, a quarter of an inch being allowed between the double bottoms for ventilation. The zinc used is never new, but always well seasoned material that has been used for screens between the fry ponds the year before. This does not dissolve and produce any salt of zinc, which is fatal to ova, and should be carefully guarded against. An empty tray is fitted into the box at the top, which is filled with ice, and kept full during the voyage, and should any hitch occur here, especially going through the tropics, all the consignment will be lost. How to obtain it. 189 Then, again, care has to be taken as to the moss that is used. It must be perfectly fresh and in growing condition. It has been noticed that when the moss goes bad or ferments the When eggs in that tray are all dead. it retains its vitality, and in reality grows a little, the eggs travel well, other things of course being equal. The ice in the uppermost tray melts slowly, and the water percolates through the moss in the trays beneath. But for the ventilation given, the delicate embryos would be in great danger of drowning. It was found for some time that the eggs in the bottom tray suffered the most, and were often in bad condition. On this account an air space was left at the bottom, and this also serves as a temporary receptacle for the water caused by the melting of the ice above. This water does not remain here, however, but escapes through a hole in the box bottom, and the box itself stands on a couple of wooden slats, one on each side, which act as feet and allow the access of air, and the same time the escape of the water. The eggs may be packed between layers of woven fabric or of mosquito netting, but this is in itself a source of danger, as decay sets in, and affects the vitality of the embryos. It may not prevent the eggs hatching, and in some cases may not do them harm, but they remain in a more healthy state during long voyages, when packed between layers of felted moss only. The unpacking is a little more difficult, but the eggs turn out better, and after all, with a little practice in unpacking, there is no difficulty. The two layers of felted moss are kept apart by the eggs which lie between them, and are therefore easily separated. After lifting the top layer of moss a piece of linen fabric may be laid over the eggs. The tray may then be inverted, and the eggs will mostly remain on the cloth when the tray with its contents is righted again. Any remaining eggs may be feathered, or otherwise picked off. Should a layer of felt fall to pieces during unpacking, as may easily happen, it is readily separated from the ova when all are placed in a bowl of water, as the specific gravity varies considerably. The eggs will go to the bottom of the bowl, whilst the particles of moss are held for a time in suspension in the water, and may be poured off with it, and then a little more water added and poured off again, the process being repeated 190 How to obtain it. until all the eggs are clean. Ova packed on layers of linen fabric may on unpacking be similarly treated. Take up the cloth by the four corners with the eggs upon it. Immerse in a bowl of water, let one side go, and gently withdraw it, and the eggs will float off. Should a few adhere to the cloth feather them off. Even on the grilles the moss may be washed off. I have seen a lot of eggs successfully laid down with much moss among A them. strong current of water being turned through the hatching boxes, the moss at once floats off, and is caught on the screen near the outlet of the box. The work is quite easily done with a little practice, but the beginner must not expect everything to go just right at first without any trouble. I have seen individuals who made great bungling at the work at first soon acquire an amount of dexterity, which enabled them to manipulate large quantities of ova successfully. Trout ova may be packed and sent anywhere in Britain, or on to the Continent, immediately after impregnation, provided the journney does not exceed forty-eight hours, and they are travelled at a low temperature. The best time of their existence for such journeys, however, is when the embryos are well developed, and the eggs are in the stage called " fully eyed." They are then near hatching, and in a mild temperature should hatch in a few days after being received. When very close to the hatching point they may sometimes be sent with safety by using ice, and even later in water in bottles quite successfully. The latter plan is not to be recommended, but may often be safely adopted in an emergency. CHAPTER X. CARE OF "ALEVINS." Word derived from the French Appearance on first hatching Very helpless atfirst Begin to pack Hides to be avoided Provide lids for the boxes Structure of alevins Cleanliness Guard against rats or mice Water insects How to detect their presence Cripples Deformities Dropsy or blue swelling Constitutional weakness Fungus Paralysis White spot Suffocation Still waters. 1I7ISH culturists have apparently by common consent adopted the French word " alevin " as the name for a newly-hatched fish, so long as it has the yolk bag or umbilical sac attached to it. ? The length of time varies much in different fishes, in some being (only a few days, in others many weeks. The temperature of the water in which they live has a great deal to do with the absorption of this sac. It has been found that in comparatively warm water a trout will absorb it in a little over three weeks, whereas, when it is very cold, sometimes more than three months is occupied in the process. When the eggs are hatched the little fish or alevins slip through between the glass bars of the grille and go to the bottom of the box, leaving behind them a mass of empty egg-shells. The grilles may then be lifted out, washed, dried, and put away for next season's use. When the shells are all removed, as described in my chapter on " Hatching the Eggs," we may turn our attention to the delicate-looking little beings which the hatching box now contains. At first they lie panting on their sides, and if disturbed they will make a start, apparently in any direction in which their heads are pointing, and entirely regardless of conse- quences. After a few vigorous movements through the water they suddenly