CULTURE OF THE SALMON. 113 



have remained at sea all winter. At Ballisodare, in Ire- 

 land, marked grilse have not returned until the expiration 

 of sixteen or seventeen months ; and the question has even 

 been mooted whether some smolts, when they go to sea, do 

 not remain long enough to pass through the grilse state and 

 become salmon before they return. 



After all the experiments, and the close observation of 

 the habits of salmon, there is still much uncertainty as to 

 its growth and its migrations. What modifications may be 

 made in series of generations by artificial hatching and 

 raising the young fish in ponds, remains to be seen. With 

 water for incubation at 50, and chopped liver, &c., fed to 

 the fry, it may make a whole year's difference in producing 

 mature salmon. In artificial culture in Scotland, the fry, 

 as a general rule, are not turned into the river until they 

 become smolts, being kept in ponds until that time, and 

 thus protected from their natural enemies, which would 

 prey upon them if turned out to shift for themselves as soon, 

 as the umbilical sac is absorbed. In the short account 

 of the salmon -breeding establishment of Stormontfield, 

 given on a succeeding page, it will be seen that a pond 

 covering an acre, and having the average depth of four 

 feet, is deemed sufficient for the feeding and rearing of 

 three hundred thousand young salmon. 



The salmon of the Danube,* which migrate to and from 

 the Black Sea, are said to grow to double the size of those 



* This is doubtless the " Sal 'mo hucho," described by Sir Hum- 

 phrey Davy in his " Salmonia." 

 10* 



