CAUSES OF DISEASE IN YOUNG SALMONOIDS. 9I3 



6. If the hatching equipment is not adapted for retaining the fry, transfer 

 each day's hatch, classifying by age, to thoroughly cleaned troughs, with such 

 number to each trough as may be held for five or six weeks. In making the trans- 

 fer use a syringe of i % to i % liters capacity, with a tube of o.oi 7 meter diameter, 

 so that the gills and yolk sac of the fry shall not be compressed. Do not keep 

 the fry in darkness or obscurity; daylight is better for them. Eliminate mon- 

 strosities. Change the water every day, the siphon outlet" serving also as an 

 auxiliary cleaner, since it creates currents in the troughs. Dispose the intake 

 at a point to produce a longitudinal motion of water. 



7. I feed the fry, to aid them in developing, beginning four days after 

 hatching. This has been my practice for some six years, and I have found it 

 good. I clean the troughs every day with a brush, called codfish tail, and take 

 out any remnants of food which the siphon outlet has not carried off. When 

 the fish are some five or six weeks old I put them in large troughs, the cleaning 

 of which is simpler, and here I feed them with beef spleen placed in small wire 

 baskets fixed at about mid depth of the trough, this to prevent the fish from 

 seeking food at the bottom and so that less shall be wasted. 



It is difficult in a large establishment to have really filtered water. No 

 filter at all is better than a bad one. 



Various devices of mine described elsewhere (op. cit.) have proved an aid to 

 the realization of the necessary cleanliness in fish hatching. I have adopted 

 also a combination trough, to be used both for the eggs during the incubation 

 period and for the fry afterwards, thus avoiding the disturbance and injury of 

 a transfer of the very young and delicate fish, while at the same time offering 

 the advantages of the currents they need, besides facilities for perfect cleanli- 

 ness. This trough is of cement and measures inside 1.5 meters long, 0.3 meter 

 deep, and 0.35 meter wide. The shape is such as to aid in cleaning, having no 

 angles, but curves only. The size is sufficient to accommodate two grilles and the 

 siphon outlet apparatus already referred to. The interior is especially designed, 

 after repeated experiment, to provide currents suitable for the eggs during 

 incubation and later for the fry, to give the latter means of equilibrium and also 

 supply them with food in a natural manner. The particles of food are always 

 in motion in this trough. The model belongs to the firm of Leune, Rue Cardinal 

 Lemoine, 28 bis, Paris. 



It is important for the fry to be in equilibrium, and not lying with gills 

 against the bottom, even though the troughs be clean, a condition which is 

 attainable if there be a current, but not otherwise. As soon as there is the 

 smallest motion giving the sensation of a current even the very young fry will 

 respond to it. This may be tested by the simple experiment of using a syringe 



"Vincent, op. cit. 



