40 OBSERVATIONS ON A SALMON RIVER 



in Scotland in 1906. " Two grilse were 

 taken from a net in the Bay of Nigg and 

 placed in sea water in a tank at the fish 

 hatchery for the purpose of discovering how 

 long sea lice will remain attached to salmon 

 in fresh water. The density of the water 

 was reduced by allowing fresh water to 

 enter. This operation was regulated so as 

 to represent approximately in time the 

 period of one flood tide. The fish showed 

 considerable distress at first, from which it 

 is natural to suppose that the transference 

 to brackish water was too rapid. 



"Dating from the time the water was 

 quite fresh the sea lice remained on one fish 

 for four days and on the other for five 

 days." ( Calderwood. ) 



This experiment shows that a fish taken 

 in the upper waters with one or two sea lice 

 attached may have been at least three or 

 four days in passing from the tide. 



I believe that, after long winter months 

 in the dark deep sea not very far from the 

 river in which they were spawned, the 



