80 



Appendices to Twenty-first Annual Report 



remarkably well stocked. No doubt the Lyon varies considerably in 

 temperature from year to year in proportion to the amount of snow 

 present during the early months of the year, but the central reaches of 

 the river are still and sluggish in a wide valley, while the upper, and 

 especially the lower, (^nd of the river is surrounded by rugged and steep 

 mountains. I can well believe that, Avhen January and February pass 

 without much severe weather, any difference between the temperature of 

 the Lyon and that of the upper Tay is insignificant, so that, except for 

 the greater volume of water in the main river, there is practically as 

 much inducement for fish to ascend the Lyon as to ascend the Tay to the 

 loch. Mr. Malloch informs me that on one occasion, having been unsuc- 

 cessful while fishing Loch Tay, he crossed over to Glen Lyon and was 

 amply rewarded, and that he then found the temperature of the Lyon to 

 be two degrees higher than the temperature of Loch Tay. 



If we turn now to the colder Garry we find that the presence of fish 

 in any numbers — the first Garry run — is not expected till April, although 

 a few fish commonly ascend as far as the deep pools of the Pass of Killie- 

 crankie in March, and that occasionally fish are present in February. 

 In 1891, for instance, Mr. Johnston caught a clean run fish in the Pass 

 on 9th February. This was an exceptionally warm season, however. 

 Mr. Johnston's note regarding it is as follows : — 



Garry, 1891. 



Temp. 





0 



Jan. 42-34 

 Feb. 42-34 

 Mar. 30-Ice 



This was an unusually warm season 

 and fish were early in the river. 

 Fishing very good on Faskally 

 water, both Tummel and Garry. 



April 48-37 





May 50-42 





This evidence, therefore, points again to the conclusion that, given good 

 running water, the warmth or coldness of a tributary induces the presence 

 or absence of salmon — that a fish ascending a main river will apparently 

 be attracted to a tributary offering abundance of warm water, and con- 

 versely will not be attracted to a tributary, the temperature of which is 

 rather lower than the temperature of the water in which the fish is already 

 swimming. To state the result more generally, one might say that in the 

 case of early fish the tributaries are not entered till their temperatures have 

 become approximated to the temperature of the main river. This is in 

 no Sense a contradiction to the finding of the preceding paper regarding 

 the presence of salmon in the Inverness-shire Garry and the Orchy, since 

 these rivers are in reality the upper waters of the main waterway. 



In dealing thus with temperature we must not, however, lose sight of 

 the great importance of an abundant flow of water. We are dealing with 

 early-running fish. I have previously noted that very few of our smaller 

 rivers have constant early runs. I would now further remark that, after 

 entering a large river, early fish very seldom — perhaps one might say only 

 exceptionally — enter any but upper tributaries^ and never enter even an 



