CHAPTER VI 



THE SALMON AND WATER TEMPERATURE 



Early and late rivers Rivers made late by man Tempera- 

 ture of the sea round Scotland Temperatures of early and 

 late Scottish rivers Temperature of water no indication of 

 seasonal character Effects of temperature on fish ascending 

 rivers Early runs of fish in upper waters, Garry and Orchy 

 Effects of cold water upon ascending fish The entrance 

 of tributaries from main river Rapid ascent of summer fish 

 Sea lice may remain attached for four or five days 



THE theories which have been advanced to explain 

 the diverse seasonal runs of salmon into fresh water 

 why in some rivers there should each year be 

 early runs of fish, and in others only late runs 

 have, with I think one exception, been based upon 

 considerations of water temperature. The exception 

 is the ingenious but unsupported theory of the late 

 Frank Buckland, that the seasonal character of a 

 salmon river depends on the length of the river in 

 proportion to the square mileage of its drainage area. 

 At the outset, in the consideration of this question, 

 I would point out that we are at the present day by 

 no means certain that the real seasonal character of 

 some rivers can be properly interpreted by the exist- 

 ing conditions. Certain rivers are described as late 

 rivers, and have no doubt been found to be late 



