928 BULLETIN OF THE BUREAU OF FISHERIES. 



treated to more frequent aeration, from eight to ten times daily. Beginning 

 with June 24 I ventured to omit the salt baths, and since no losses resulted I 

 decided to omit the baths entirely and confine myself solely to aeration ; rightly, 

 too, as I saw afterwards. On June 16 the fish were all sent away in a cask, fresh 

 and healthy. The cask contained 63 liters of water without ice. Duration of 

 transportation, i hour and 30 minutes by wagon, i hour and 30 minutes by 

 rail, 2 hours and 30 minutes by wagon, in all 5'^ hours. At the pond 3 fish 

 were found dead, wounded by lumps of ice which were put into the water in the 

 railway car without any ice bag. 



SUMMARY AND CONCLUSION. 



I come to the following conclusion from the above-mentioned experiments : 

 A means for the radical prevention of Costia necatrix in salmonoids under cul- 

 ture is to be found in the abundant and constant introduction of atmospheric air 

 into the living water; in other words, abundant and constant aeration. 



Can deeply infected fishes be cured and saved? I doubt it. I have never 

 seen that surface wounds and abrasions of the skin healed; fungus invariably 

 assailed the injured places and extended over the neighboring areas more and 

 more until there ensued weakness, difficulty of moving, and lastly death, while 

 deep wounds, bites, thrusts, and cuts were often found healed and leaving scars. 



Costia lives and increases on the skin and on the gills and destrovs their tissue. 

 Cure is always possible in the beginning of the infection, and the following phe- 

 nomenon may be pointed out : All the fishes presenting a suspicious appearance — 

 i.e., showing signs of weakness and discoloration and refusing food — were taken 

 up by me with a gauze hand net and washed out in the water flowing from the 

 hatching troughs. There was always water around the hatching boxes 3, 5, to 

 ID centimeters deep, according to the height of water in the pond. Here all 

 around the breeding troughs and in the narrow waterflow to the pond there came 

 again and again small fishes, mostly 5. joniinalis of the same size as in the boxes, 

 about 50 in June, and these seemed to be quite healthy, catching greedilv at the 

 crustaceans falling from the boxes. As it was impossible for them to come 

 through out of the boxes, either these were cured fishes or I have taken unin- 

 fected fishes out of the boxes. 



It need not be mentioned that Costia spreads more rapidly when the frv are 

 crowded and that the rise of temperature above 10° C. accelerates the progress 

 of the infection and its communication. 



