^66 Mr D. Ellis on the Natural History of the Salmon, 



tion, till September ; and others are said not to repay the ex- 

 pence of fishing them till March, or even April, and to yield 

 the best fish in May and June. 



This difference of time, in the appearance of the salmon in 

 different rivers, cannot be ascribed to any difference in geogra- 

 phical position, as far as regards these islands ; for the Ness, 

 which is one of the earliest rivers in Britain, is situate in the 

 highest latitude. It must therefore be sought for in some local 

 circumstances and conditions, which more or less adapt particu- 

 lar rivers to the taste and habits of the fish. Now, the Ness, 

 we are told, flows out of a lake of great depth, which never 

 freezes. In the year T807, Mr Alexander Fraser states, that, 

 at Inverness, the temperature, for ten days, was from 23° to 30°, 

 or more, below the freezing point ; yet this intense cold made 

 no impression either on the river or the lake ; and clean fish, he 

 adds, pass up the Ness every month in the year, except May 

 and June *. It is probable, therefore, that the comparatively 

 high temperature of the Ness, during the winter months, in- 

 duces salmon to enter it at a time when they are repelled from 

 other rivers, which, either from their shallowness, or from re- 

 ceiving large quantities of water produced by the melting of 

 snow, are reduced to a temperature unsuited to the economy 

 and habits of the fish. It is well known, says Sir G. Macken- 

 zie, that, while snow is melting on the mountains, few fish go 

 up rivers. Whether it be its coldness, or any other cause, that 

 makes them dislike snow water, I cannot tell ; but the fact has 

 been noticed, and is consistent with my own observation -j-. 



As these fishes seem thus to decline entering rivers when 

 much reduced in temperature, so, at other seasons, they seem 

 equally to avoid them when their temperature is too high. 

 During the summer season, the water, in many rivers, becomes 

 so small, and gets so hot, that the salmon will not enter them, 

 but linger upon the coasts, and about the mouth of the river. 

 In one very dry and warm season, when stake-nets were in use 

 in the estuary of the Tay, the salmon, says Mr Halliday, did 

 not even approach the highest stake-net during the neap-tides ; 

 but, when the spring-tides became high, the fish then came up 

 to those nets, and were taken ; when, again, these latter tides 

 fell off, the nets on the lower parts of the frith caught a great 

 • Report II. p. 43. f Report I. Appendix, p. 17- 



