250 THE ANGLER-NATURALIST. 



run " fish, and are then in the most perfect condition both 

 for the rod and the table. 



The marks by which a fresh-run fish may be known are, 

 the bright, silvery hue of the belly and sides, and the com- 

 paratively loose adherence of the scales more particularly 

 in the Grilse. In the case also of Salmon just fresh from 

 the sea, a species of parasite, or sea-louse, may be fre- 

 quently found attached to the fish. These, however, are 

 killed by a few hours' contact with fresh water. 



In some rivers the ascent and spawning-time of the 

 Salmon are much earlier than in others. This is often 

 the case in rivers issuing from large lakes, in which the 

 water has previously undergone a sort of filtering process 

 and has become warmer, owing to the greater mass and 

 higher temperature of its source; whilst, on the other 

 hand, streams which are liable to be swollen by the melting 

 of snows, or cold rains, or which are otherwise bleak and 

 exposed, are later in season, and yield their principal supply 

 when the great lake rivers are beginning to fail. Two 

 of the Sutherland streams offer good examples of these 

 operating causes. One, the Oikel, springs from a small 

 exposed alpine pool some half mile in breadth ; the other, 

 the Shin (a branch of the Oikel), takes its rise in the deep 

 sweeping waters of Loch Shin and its tributary lakes. 

 The Shin joins the Oikel about five miles from the sea. 

 Early in the spring, all the Salmon entering this common 

 mouth diverge at the junction, pass up the Shin, and thus 

 return, it would appear, to their own warmer stream, 



