XVI.-THE ENEMIES OF FISH.* 



By Bap^on de la Valette St. Geokge, 

 Professor of Anatomy and Director of the Anatomical Institute at Bonn. 



Bead at a meeting of the German Fishery Association, Berlin, March 31, 1879. 

 [From Circular No. 3 of the German Fishery Association, Berlin, May 14, 1879.] 

 [Translated by Herman Jacobseii.] 



War is the ^vatch-worcT of the "vrhole of organic nature ; there is a con- 

 stant war of all organisms against outward unfavorable circumstauceSy 

 and there is constant war among the different individuals. The seed- 

 grain which falls into the ground, the worm crawling on the earth, the 

 butterfly hovering over the flower, the eagle soaring high among the 

 clouds, they all have their enemies — outward enemies threatening their 

 existence, and inward enemies eating their life and strength. 



Even fish, which claim our special attention, are by no means per- 

 mitted to spend their life in peace. Plants and animals endanger their 

 very life, and when they have been fortunate enough to escape these, 

 man comes and seeks to catch and destroy them with numberless arts 

 and tricks. 



Confined to a special sphere of life, the water, they frequently do not 

 find in it the necessary conditions of existence. In their very cradle, so to 

 speak, that is, in the egg, the tender germs, scarcely awakened to life, 

 are thieatened by a dangerous enemy belonging to the lowest grades of 

 the vegetable kingdom. This is the much-dreaded Saprolegniaferax; in 

 an incredibly short time its long threads envelop the egg, choke it, and 

 destroy it. 



The best preventive is an amjile and continuous supply of cold water 

 of a temperature of about zero, a dim light, and the immediate removal 

 of spoiled eggs. Using a brush only destroys the spurs or threads of 

 the ^aprolegnia and consumes too much time. 



These parasitical plants may prove dangerous even to older fish, for 

 I have observed them on full-gro^vu trout. But, as Dr. WittmarJc says 

 ui his excellent treatise on the enemies of fish, the j/ropter hoc and post 

 hoc should be well distinguished. I believe that such fungous forma- 

 tions are only found in fish which are worn-out or have been weakened 

 by sickness, and that in such cases it accelerates their death. It is 

 well known to all pisciculturists how important it is to keep aU ponds 



* Ueher die Feinde dtr Fiiche, Vortrag des Herrn Freiherrn Ton la Valette St. George. 



509 



