RESULTS OF SALMON MARKING 87 



can scarcely be caught in the small streams of the 

 West Highlands, so quickly do they get away to the 

 sea. In a large river, on the other hand, or in any 

 river which broadens out into a large lake or into 

 deep pools, the descent of female kelts at least is 

 very slow indeed. A large number of recaptures of 

 such descending kelts have been made in the Spey 

 and Tay, and it would appear that so long a time as 

 three months may be occupied in descending forty 

 miles of river. Grilse kelts, as already stated, descend 

 to the sea with some promptitude, but as salmon 

 grow older their descent after spawning becomes 

 slower, although this appears to be less true of males 

 than of females. Large female kelts linger longest. 

 The discovery of this habit makes a considerable 

 difference in our interpretation of the increments 

 put on in the sea. One fish may relatively be so 

 much longer in reaching the sea than another even 

 if both be, say, short period fish. In judging of in- 

 crease from kelt weight this uncertainty of knowing 

 when the sea was entered is always present. We 

 may have in long period fish considerable uniformity 

 of increase, since an actual delay at starting may in 

 the longer period be made up. For instance, in 

 Helmsdale long period fish of 480, 498, 504, and 506 

 days we find increments respectively of 9, 9, 9, and 



10 Ib. Yet clearly there may also be great variation. 

 In short period fish we have similar results. Two 

 Brora fish were taken, the one in 162 and the other 

 in 163 days : the one had added 4 Ib., and the other 



11 Ib. Many Tay fish recaptured are described as 

 " bull-trout." In the Tay a bull-trout is in reality a 



