CAUSES OF DISEASE IN YOUNG SALMONOIDS. 



By EUGENE VINCENT, 

 Fish CuUurist, Aquarium of the Trocadero, Paris. 



[Translated from the French.] 



The common trout and its varieties are especially subject to disease of 

 the gills, and other salmonoids likewise are not exempt from it. Such disease 

 consequently presents great difficulty to fish culturists, who must find means 

 of combating it. Another frequent trouble is the epidemic which may be 

 called "staggers." The effective measures in both cases are those of preven- 

 tion rather than attempt to cure; and the best means of prevention is perfect 

 cleanliness of equipment, from the beginning of the hatching period throughout. 

 To maintain the necessary cleanliness, however, is a question of style of appa- 

 ratus as well as unremitting care. 



DISEASES OF THE GILLS. 



F.\ULTY HATCHING EQUIPMENT AND CONDITIONS. 



As fish culturists well know, the styles of apparatus for incubating eggs 

 of the salmon species are very numerous. In France the most common equip- 

 ment is the Coste trough and its derivatives, consisting of a kind of rectangular 

 zinc box 0.50 to 0.60 meter long, 0.25 meter wide, and 0.20 meter high, with 

 two partitions of perforated sheet iron, the one serving to admit the water 

 from below, the other allowing it to pass out from above. Into this box is 

 set a glass grille of dimensions to fit. 



I have heard much in praise of all varieties of apparatus, but I have heard 

 little concerning their disadvantages and dangers. It is of these latter that I 

 shall speak. 



First of all, I consider the equipment bad which does not allow the fish 

 culturist to see what is taking place below the grilles on which the eggs are 

 resting or permit of cleaning without disturbing the eggs. 



We are told that there are currents of water in this apparatus, which 

 receive as much as one-half liter of water per minute. There can be no currents 

 of water in these troughs, however, especially in those with partitions; there 

 is, to be sure, a change of water, but there is no current which would bring 

 about a flow throughout, and this may be easily shown by putting into the 

 water coloring matter or thin strips of paper. And it is precisely the absence 



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