THE SCALES OF SALMON 107 



redds or destroy the eggs in the early and delicate 

 stages. If these high tributaries, where in many 

 cases the finest spawning grounds are to be 

 found, are not occupied by the spring fish, it some- 

 times also happens they are not occupied by the 

 quick running summer fish which follow, and at the 

 same time it is well known that the available lower 

 spawning grounds are not infrequently occupied by 

 successive runs of late fish, so that to some extent 

 one set of spawners undo the work of fish which 

 have preceded them by turning up gravel already 

 protecting eggs. 



The kelts of the spring fish by getting away down 

 stream at an early date have also a better chance 

 of reaching the sea before the time at which salmon 

 disease makes its worst appearance. Such kelts 

 should be respected and carefully handled by any 

 into whose hands they may fall. Like the bread 

 cast upon the waters, they will return after many 

 days. 



The observations of Mr. Hume Patterson * on the 

 subject of salmon disease show that it is possible for 

 an apparently healthy fish to be infected by the 

 real cause of salmon disease — the bacillus salmonis 

 pestis — since, if the fish has been previously diseased 

 in fresh water, a sojourn in the sea, although it kills 

 saprolegnia ferax, does not kill the bacillus. His 

 observations also show, however, that the entrance 

 of the bacillus to the tissues of the salmon is most 

 readily gained when fish are injured and sickly. 

 The organism itself has been found in river water, 



* " The Cause of Salmon Disease," Fishery Board for Scotland, 1903. 



