parts finally become perforated, especially in slichtly "sour v.-ater", or in water, rich 

 in carbonic acid (pH is smaller than 7). The indicated therapy is obvious. The perfor- 

 ations heal — in suitable v/ater — upon primarj' intent within about 7 months, leaving slight 

 scars upon the skin. 



Rachitic Shortenin'-^s and DefoniLJ,.ties of Gill covers and Bones . A peculiar affliction, 

 quite often of epidemic proportions. It will be noticed among carp fingerlings but also 

 among strongly fed rainbov/ trout fingerlings. The gill covers are shortened, at times, 

 the edges of the covers are "rolled up", at other times the covers beccaie arched. Neither 

 parasites nor hereditary factors alone are the cause of this affliction, accordiiig to 

 Schaeperclaus(1929). It seems obvious that rachitic disturbances of the juvenile bone 

 structure bring on this sickness. In the first place, various forms of contracted ventral 

 fins and anal fins, quite often even numerous deformations of the spinal column appear 

 regularly in combination with the different gill cover defects. And then again, the 

 fish v.'ill recover from all of these defects by fall, which could not be the case with 

 defects conditioned by heredity. Still, it is to be presumed that a rachitic tendency 

 is hereditary. There is also the possibility that these defects already start in the 

 egg as the result of yolk swelling due to chemical-physical influences. It has also been 

 occasionally supposed that overripeness of the eggs causes a rolling in of the gill cover 

 in carps. The outbreak of the disease is greatly favored by supplementary feeding (lack 

 of vitamines) and neglect in the proper maintenance of the ponds (shaded ponds). For 

 prophylactic reasons, parent fish of sickly disposition are to be eliminated. The brood 

 ponds ought to be properly cared for and feeding of the youngest brood should be avoided. 

 ScheurinT sees in rachitis the cause of gill cover swelling* 



Faulty skeleton development through hereditary disposition . One will find, in 

 almost every carp fishery a fev/ fish which through hereditarj' disposition are lacking 

 in some fins or are Tdthout fins altogether. Wunder lately called special attention to 

 this. From my ovm observations of such cases, I would say that lack of ventral fins 

 predominates. Abundant other hereditary malformations occur often. Occasionally, I 

 found numerous contractions and deformities of the spinal column. Schr&der has dealt 

 with this subject exhaustively. Such carps, just like those with one or multiple 

 kypholordoses can therefore become fatalities, because they are regarded as being 

 especially compact and high backed and therefore of particularly high value. It is 

 self-r?vident that all fish with hereditary deformities and with latent hereditary 

 tendencies are to be summarily eliminated. 



Deformities in trout brood . Deformities of the heads and tails, occasionally multiple 

 heads and tails are observed in trout brood, Mrsic ascribes the condition to abnormal 

 maturity of the eggs and filler sees lack of oxygen and other injurious factors during the 

 development sta^e as the cause. 



Dropsy of the vitelline sac . The cause for this frequent phenomenon in the trout 

 brood (see Fig, 63) is mostly ascribed to a change of water and injury to the eggs during 

 transportation. Scheuring found 100 percent of vitelline sac dropsy in the progeny of a 

 rainbow trout which had been injured by a heron. 



Injuries from cold temperatures . According to Staff and Scheuring, if the water 

 temperature drops belov; ^^"C, v;hich can easily be the case in hibernation ponds with 

 melting ice and snow, then the carps which up to this time have been remaining on the 

 bottom in a state of semiconsciousness (winter sleep, change into a state of paralysis 

 and rigor). They lose their equilibrium and are carried up and away by the slightest 

 current. In this way they easily come into contact with the ice on the surface, whereby 

 they receive skin injuries. But even without contact, strong excretions of mucus and 

 nose affections easily occur and are follonved by the attacks of one-»celled skin parasites 

 and mold fungi, especially in the case of one and two year old carps. 



I have never been able to determine, in spite of my many investigations on sick 

 fishes, a chilling of the skin with separation of the musculature as described in text- 

 books of fish pathology and said to be caused by the transferring of fishes out of warmer 

 water into L to 5°C. colder vrater. I also doubt that that kind of chilling occurs or is 

 of importance in practice. Verj"- strong temperature differences are naturally injurious, 

 as the carp ergs also shov/ (see Chapter IV,B,2). 



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