2o6 ANNALS OF SCOTTISH NATURAL HISTORY 



early running of fish, and my attempt to interpret the causes 

 thereof, and Sir Herbert's difference of opinion thereanent, 

 and his examples of the river Luce and of the Amhuinn 

 Aodh, there is another factor which ought not to be lost 

 sight of, and that is the temperatures of the salt and fresh 

 waters at the times of the runs of fish. Of this I had 

 meant to speak later on, but the nature of Sir Herbert's 

 criticisms almost forces me to enter upon it now. The whole 

 question comes, I think, before we are quite prepared to take 

 it up. 1 



Here it is : Do Salmon and migratory Salmonidae run 

 from a colder sea to a warmer river ? Do they run from a 

 warmer sea to a colder river ? Or do they run from sea to 

 river when the temperatures of the two are most nearly 

 assimilated ? 



North and East Coast rivers are early. They run with 

 a cold, snow-laden current into a cold North Sea. West 

 Coast and especially North-West rivers, i.e. west of Cape 

 Wrath, run shorter courses, and are mostly clear of snow- 

 water not much before June, and are later rivers. There 

 these rivers hurry down to meet the warmed-up waters of 

 the Gulf Stream. I do not know if I am quite correct in 

 saying that the rivers south of Clyde are earlier than those 

 north let me say- of the Mull of Cantyre ; but from what 

 I have heard of the Stincher and the Doune, these rivers do 

 yield earlier fish. North of Clyde, the exceptionally early 

 rivers are the Awe, or rather the Orchy and the Lochy ; 

 and there is reason to believe that the Gruinard was at a 

 prior period of its history a much earlier river than it has 

 been since " Kennedy's Commission " and the initiation of 

 bag-nets in the bay. Now, I would like to ask Sir Herbert, 

 Is it possible that the shallow area of the Solway Firth has 



1 The depths at which Salmon lie in fresh water may, I believe, yet be 

 proved to be dependent upon temperature, and the temperatures of surface and 

 bottom of the pools to be dependent upon the force of the currents running into 

 and out of the pools : in other words, upon the aeration caused by falling or mov- 

 ing water. The greatest ascertained depth at which Salmon lie I believe to be 

 about 12 feet, and it is known that in the deep pool of the Deveron at Alva 

 Bridge the nets are used only down to the depth of 12 feet. The Alva Bridge 

 pool is profoundly deep it is said 60 feet (?). I would be obliged by any one 

 giving thoroughly reliable statistics of Salmon lying at greater depths than 12 

 feet, if such can be ascertained. 



