( 



2 2 F. day: early and late salmon rivers. 



perhaps about half a mile in breadth; while the Shin, which is a tribu- 

 tary of it, coalescing at about five miles from its mouth, takes its rise 

 in Loch Shin, a large and deep extent of water, and connected to a 

 chain of other lochs. The river Shin, from its course between the 

 loch and the tideway of the Kyle, has its temperature several degrees 

 higher in winter than the waters of the rivers Oykel and Cassley, with 

 which it mingles on entering the Kyle ; and the temperature is several 

 degrees lower in summer than the waters of the long-run, hill-collected, 

 and sun-heated rivers. ' To be sure respecting the temperature, a 

 thermometer was regularly kept. The salmon soon finds out the 

 warmer side of the estuary, and the river from which that warm water 

 flows. It is well known that salmon during the winter and spring 

 months, when the water of the warmest river is cold, always run on 

 the sunny side of the estuary, that is, as much as possible on the 

 north side, and there during that time the run of fish is to be found. 

 In the summer months, that is, after the ist of May, the fish run on 

 the opposite side of the estuary. The high temperature of the water 

 at that time induces them to seek as much as possible to get under 

 the cool sliade of the south banks, where there is the least influence 

 of the sunbeams.' Of the many rivers going into the estuary, the 

 only one which produces early fish is the warm Shin. 



Dr. Heysham was of opinion that in Cumberland salmon at first 

 spawn in the warmer streams, leaving the snow-fed ones until later on ; 

 consequently, during the winter and spring, they prefer the Eden to 

 the Esk, the Caldew, or the Peteril. The two first rivers enter the same 

 estuary, their mouths being merely separated by a sharp point of 

 land, yet there is scarcely an instance of a new salmon ever entering 

 the Esk until the middle of April or beginning of May. The 

 fishermen assert that the Eden is considerably warmer than the Esk, 

 the latter having a more stony bed, shallower stream, and broader 

 expanse. When snow-water comes down the Eden the fish will not 

 ascend ; by the beginning of summer the temperature of the two 

 rivers is about the same. The Peteril joins the Eden a little above, 

 and the Caldew at Carlisle ; yet up these rivers the salmon never run 

 unless in the spawning season, and even then in no great numbers. 



I will now give an instance of a river which was originally an early 

 one, but was found to become a late one by the Earl of Home, who 

 in 1837 observed 'that in the Tweed a very great change had taken 

 place within these twenty or thirty years • a considerable portion of 

 the breeding fish not arriving into breeding condition until long after 

 the time they had formerly been in the habit of doing so.' The first 

 inquiry here should be whether this had happened consequent upon 

 any changes in the river, the placing of artificial obstructions in its 



Naturalist, 



