72 THE SALMON. 



bull-trout is seen to be entirely independent of the sal- 

 mon and the grilse, being found in great multitude 

 where they are almost entirely absent, and vice versa. 

 Now, if the grilse were a species as distinct from the 

 salmon, or Salmo solar, as is the bull-trout, should not 

 we find similar results, some rivers abounding with 

 grilse, yet almost without salmon ? But what is found 

 is not this, but the contrary : many or few grilse imply 

 many or few salmon. 



Mr. Mackenzie makes a sort of loose or partial denial 

 of this fact, by adducing the statement, that the Shin in 

 Sutherlandshire, a valuable salmon river, contains so few 

 grUses that they " are not calculated upon as part of the 

 commercial produce." But we have ascertained that 

 this statement, so far as it is correct, is entirely explained 

 away by the fact that the Shin river is fished, not by 

 nets, but by a cruive, the hecks of which are of such 

 width as to permit most of the grilse to pass. This, of 

 course, accounts for the grilse forming a very small part 

 of the commercial value of the river ; but it does not 

 prove that few grilse frequent the river ; in point of fact, 

 they abound in much the usual proportion to the salmon, 

 and as many as twenty have often been killed by a 

 single rod in one day. Besides, the fact, which we do not 

 deny, that the proportion of grilse and salmon captured 

 varies greatly in a comparison between different rivers, 

 would not in the slightest invalidate our argument, 

 nor establish Mr. Mackenzie's ; because the proportion 

 of captures of each kind is regulated not entirely by the 

 numbers of each frequenting the river, but by various 

 other circumstances, both 'artificial and natural. For 



