XXIV.-TREATMENT OF YOUNG SALMONOIDS AND COREGON1 

 FROM THE TIME THEY LEAVE THE EGG TILL THEY ARE FULLY 

 DEVELOPED AND CAN BE PLACED IN OPEN WAFERS. 



By Director Haack:.* 



[From Circular No. 1, 1880, of the Deutsche Fischerei-Vereiu, Berliu, February 12, 



1880.] 



Young salnionoids and coregoni, after having left tbe egg, remain in 

 the hatching apparatus until the umbilical bag has been completely con- 

 sumed, and they have thus been enabled to swim about and seek their 

 food. 



Immediately after the hatching process and for some time after it, it 

 will be well to decrease the influx of water a little, because otherwise 

 the weak and helpless little fish are pressed against the grate and are 

 injured. Gradually the influx of water may be increased in the place 

 where the salmonoids are kept, and after a few weeks have elapsed it 

 can scarcely be strong enough, for the fish have then become so strong 

 that they can easily resist the current. 



For the tender coregoni, however, the influx of water must never be 

 very strong, if losses are to be avoided. Nor can the exit-grate ever be 

 too fine for these little fish. The exit-grate should be carefully fixed 

 with putty all round the edges (common putty will do), for even the 

 smallest opening may become a door of escape to these diminutive and 

 scarcely visible fish. 



Some time after being hatched the young salmonoids lie perfectly 

 helpless at the bottom of the hatching apparatus, only their pectoral 

 fins are in constant motion to admit fresh water to the gills. From time 

 to time such a young salmon or trout rises to the surface and paddles 

 about with considerable difficulty, but only to sink again immediately 

 to the bottom. 



The young coregoni, however, immediately after being hatched, swim 

 about quite lively. Scarcely anything is visible of this little fish except 

 the head with the two large eyes ; the body, thin as a thread and trans- 

 parent as water, can only be seen by a very close observer. 



During the early stages of their existence young salmonoids generally 



* Herr Director Haack: "Behandlung der ausgesJiliipften jungen Salmoniden und 



Coregonen lis zu Hirer volligen Entwickeung und das Aussetzen derselben." [Translated by 



Herman Jacobson. 1 



687 



