Fig. 71. Application of the lysol bath on two-summer carps in the 



large fisheiy. Large quantities of fishes can be bathed in a short time. 



watch this dangerous parasite, since tench stock attacked by Ergasilus will be unsalable 

 in the future, Ergasilus is about the size of a pinhead and in the spring it develops 

 two small streak-like egg sacs on its hind end. From the eggs are hatched free swimming 

 larvae, which again attach themselves on the gills (Neuhaus), especially in the height 

 of summer. With a strong attack of one hundred to several thousand parasites, severe gill 

 injuries and mold invasions occur even in larger fishes, which can lead to emaciation and 

 asphyxiation. 



All infected fishes must be removed, and in particular no parasite carrier must be 

 present in tench spawning ponds, and the brood must not be later kept with infected fishes. 



F. General Viewpoints for Combating Fish Diseases . 



The foregoing detailed discussions of the most important pond fish diseases, shovf 

 how closely related the comparison of diseases of fish and plant (as stated in Chapter XV) 

 is to the combating of fish diseases also. The treatment of individual sick fishes plays 

 no role, mass treatments of fishes cannot often be applied because of the small capital 

 value of the individual animal and the difficulties of handling them. 



More important therefore is the isolation of the resulting disease foci, the pre- 

 vention of disease spreading by the rapid destiniction (cremation or burial) of all dead 

 and diseased fishes, of all disease carriers (snails, for example) immediately after the 

 fish out. 



Of the greatest significance, however, is the prevention of disease occurrence. 

 This must begin with the selection of particularly disease-resistant parent fishes. The 

 favorable hereditary factors are to be brought to development and to be further strength- 

 ened by the provision and maintenance of the best living conditions in summer as well as 

 ■winter, by the best pond care, careful hibernation and feeding, protective handling of 

 fishes with all transplantations. Finally it is the task of the manager to prevent the 

 introduction of diseases if possible and the transfer of disease from one year to another 



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