582 REPORT OF THE COMMISSIONER OF FISHERIES. 



not to undertake its culture he has the following - to say on this subject 

 (Prince, 1897, p. 35): 



German carp are especially subject to parasites and contagious diseases. From 

 their omnivorous and lethargic habits no fish are so readily attacked by diseases and 

 parasites as carp. The "fish leprosy," described by Blake as a fungoid growth 

 which spreads over the whole skin, turning the fish white and rendering it most 

 unhealthy and a source of disease to all other fish, is essentially a disease of the 

 German carp. Frank Buckland studied some of the diseases of these fish, and 

 among others enumerated one malady which he called small-pox in the carp." 



Tapeworms and other disgusting endo-parasites occur most plentifully in carp. 

 One described by Harrington Keene taken from a carp of 16 pounds weight meas- 

 ured no less than 45 feet m length. Of all fresh water fishes the German carp are 

 the most subject to external and internal diseases. This is, in fact, unavoidable in 

 a family like the carps, with sluggish habits, a fondness for coarse and loathsome 

 food, and a preference for muddy and almost tepid waters. 



If an}^ of the above is from Professor Prince's own observations I 

 feel quite certain that he can not, at all events, have made them in 

 this country. And if the German carp in Europe has been found to 

 be subject to a number of diseases and parasites, it must be remem- 

 bered that this is a subject upon which comparatively little is known 

 in general, and that the car]), being a cultivated fish, has afforded 

 opportunity for close study which most others have not. Certain it 

 is that some of the fungus diseases to which he applies such awful 

 names will attack almost any fish or other water animal under condi- 

 tions unfavorable to the latter, and especially if there happen to be 

 any abrasions of the integument. The carp's hardiness in this respect 

 is one of its chief characters, allowing of its cultivation in ponds and 

 small enclosures, conditions under which many of our native fish 

 would succumb to fungus and other diseases in a short time. Then, 

 too, contagious diseases, strictly speaking, are, according to present 

 knowledge, extremely rare among fish, and I am not aware that any 

 has yet been found which attacks the carp. The whole tone of Pro- 

 fessor Prince's paper leads us to suspect that if he were studying a 

 fish malady he would call it by some such name as smallpox in car}), 

 whatever title he might use to designate it in other species. 



It remains now to consider certain enemies which menace the fish, 

 especially those which may attack them while the}' are in the ponds. 

 These are in reality very few in such ponds as are in use in this coun- 

 try, since the impounded fish are till adults, and the adult carp has 

 comparatively few serious natural enemies. With the young fish it is 

 different, and the regular carp culturist has, of course, to deal with all 

 these factors. The eggs are exposed to a great number of dangers, and 

 especially are they open to the attacks of minnows and other small 



"The disease here referred to is apparently due to one of the Myxosporidia called by Hofer (1896, 

 1896a, 18966) Myxobolvs cyprini. This appears to be not uncommon in European carp ponds, but I am 

 not aware of its ever having been reported on the carp in this country. I have not had opportunity 

 to examine the recent handbook of fish diseases by Hofer (1904). 



