TRANSITION OF THE SMOLT INTO THE GRILSE. 



size than the other, but in order to do so, does not 

 necessarily require a longer period of time. They are 

 also, in respect to their feeding, of different habits. In 

 fresh water, the sea-trout is a voracious feeder, especially 

 during river-floods, and when the water is high-coloured, 

 whereas the salmon, on such occasions, refuse every 

 variety of sustenance. Even the parr or infant fish is 

 then more capricious than usual. This is the reason 

 unquestionably, why, before its descent to the sea as a 

 smolt or black-fin, it is generally of smaller size and 

 weight than the sea-trout smolt or orange-fin. The 

 latter, while in fresh water, is as voracious in its habits 

 of feeding as the common river trout, and consequently, 

 at the time I speak of, grows with greater rapidity. On 

 its entrance, however, to the sea, the change, as respects 

 its food, being one of kind and quality, not so much one 

 of quantity, its growth (irrespective of its being affected 

 through specific inferiority) although proceeding at an 

 improved rate, does not bear any proportion to that of 

 the salmon. 



The black-fin smolt, after its descent into the salt 

 water, until the period when it ascends as a grilse, does 

 not, I have reason to believe, wander to any great dis- 

 tance from the breeding river. The limit of its pere- 

 grinations coast-wise extends, in the average, to ten or 

 twelve miles, but where there is a firth, such as that of 

 the Forth or Moray, its range is much greater. The 

 grilses of July and August, which ascend in shoals, 

 proceed from localities very near the mouth of the breed- 

 ing stream, where they are naturally more crowded. 

 The late-running fish of this description are chiefly strag- 

 glers from a greater distance, or such as are kept back by 

 the presence of stake-nets at the entrance of the river. 

 These, during calm, clear weather, they readily detect, 



