CHAPTER VI 



THE SALMON AND WATEE 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 



