FISH CULTURE. 923 



an additional advantage, as the larger the screen the less liable it is to clog up with leaves 

 and moss, and the greater will be the volume of water passing through it. 



Screens. Screens may be made of common wire painted with tar as will be 

 described hereafter of copper wire, or of galvanized iron wire. The last is the best, as it 

 will last longest in proportion to its cost. The screens for keeping the small fry should be of 

 fourteen threads to the inch, and for one-year-old fish five or six threads to the inch. Incline 

 the screens at an angle of forty-five degrees, the top being farthest down stream. By inclining 

 the screens in this manner, a greater surface is exposed to the water than if they were placed 

 perpendicularly. The sockets should be so made that the screens will fit tightly, and yet be 

 easily taken out to clean. 



A very good screen for two or three-year-olds can be made from strips of lath planed 

 and nailed to a strong frame, with quarter-inch openings between them. Or, what is better, 

 the slats should be at least four inches wide, so that if a leaf strikes against them it will catch 

 without obstructing the flow of water and lie flat against a single slat, or if it reaches over 

 the edge it will be carried through by the current striking upon one end. It cannot lap 

 around the slat as it would if it were smaller. As for the width of the slats from one another, 

 the point to be guarded against is the fish running their heads through far enough to strike 

 their eyes, which will produce blindness. The distance they are to be apart will depend, 

 consequently, mainly on the size of the heads of the fish, and as fish grow at different rates 

 of speed it will not do to go merely by their age, but for fair-sized fish an opening of about 

 five-eighths of an inch will answer. This refers to the upper screen ; the lower screen, that at 

 the foot of the pond, may be larger, as the fish are more cautious about descending where 

 they cannot see their way, just as a man will climb a hill -in the dark at his best speed, but 

 will go down very cautiously. 



Water Supply. It is immaterial what kind of water is used, whether hard or soft. 

 Neither will so-called &quot; mineral water &quot; hurt the trout, unless the water is very strongly 

 impregnated. Trout have been known to live and thrive in a stream one-sixth of whose 

 volume was supplied by a strong sulphur spring. The essentials are that the stream shall be 

 reasonably pure, the volume of water nearly uniform, or so arranged that the supply taken 

 from it is uniform, and the temperature between 36 and 65. 



One peculiar fact has been noticed in reference to the eggs, which is important to those 

 persons who collect eggs to impregnate and sell. The shells of those taken from trout living 

 in limestone waters are found to be thicker and harder than those obtained from soft waters. 

 This may come from the lime in the water, and is an advantage in rendering the eggs more 

 easy to transport with safety than where the shells are very delicate. 



The supply of water necessary for a given number of trout is yet unsettled. For a series 

 of ponds turning out one thousand large fish yearly, the water supply should fill a four-inch 

 pipe. This question will be treated more at length hereafter; but it is always safe to have 

 , as much water as possible, for within reasonable limits one can hardly have too much that 

 is to say, if the dams and sluices are solid, and the screens do not clog. It must not be for 

 gotten that abundance of pure water is as essential to fish, as abundance of pure air to &quot;man. 



In saying that ponds must not have a gravelly bottom, we do not mean there should be 

 no gravel. The trout must have access either to the raceway or some other spot of gravel to 

 rub off parasites. This they cannot do if the bottom is wholly of mud, and they are excluded 

 from the raceway. 



The Hatching House. If only a few eggs are to be hatched (say eight or ten thou 

 sand) no hatching house is necessary. The troughs may be placed in the open air, in any 

 convenient place, and covered with a wire screen to keep out rats, mice, and ducks. A light 

 board cover must then be laid over them to shed the rain and snow and keep the eggs from 

 exposure to the sunlight. A hatching house is much more comfortable to work in. A stove 

 may be put in it and a fire started occasionally for warming one s fingers, but it is not needed 

 for hatching purposes, as spring water in these latitudes is warm enough. The house may be 

 constructed of rough boards, or as expensively as you choose, but care should be taken to 

 have a water-tight roof, as drops of water leaking through and falling into the troughs will 

 kill the eggs underneath. Its size must be regulated by the number and extent of the 

 troughs. 



The windows in a hatching house should be few in number and provided with curtains or 

 shutters, as the sun shining upon the spawn will kill it. Not that a few minutes exposure to 

 the rays of the sun will hurt the eggs, but a few hours exposure certainly will. Perhaps it 



