76 The Natural History of the Salmon. 



a safe guide to ascertain the real history, travels, 

 and position of a given fish. These clean-run fish, 

 therefore, in my opinion, are those who have laid 

 up a sufficient amount of fat during the time they 

 have remained in the sea (dating from the kelt 

 stage) to last them during their stay in fresh water, 

 and I fancy (although I have no direct grounds as 

 yet to prove it) that they are the early kelts of the 

 previous year who have reached the sea, say, in 

 January, 1868, now reappear as clean-run fish in 

 February, 1869, or may be, as large fresh-run fish 

 in 1870. Much, however, depends on the quantity 

 and quality of food they find in the estuary. There 

 are, I understand, enormous numbers of smelts in 

 the estuaries of the Dutch rivers, and the food 

 afforded by these, combined with other causes, 

 goes a long way to make the Rhine fish lay up his 

 stock of fat quickly, and therefore renders it ready 

 to proceed all the earlier on its upward pilgrimage. 

 I believe large numbers of smelts are found in the 

 estuary of the Tay. The early fish, therefore, having 

 laid up a sufficient quantity of fat for their inland 

 sojourn, do not wait till the descent of the autumn 

 floods, but they avail themselves of the spring 

 floods, being tempted by the state of the tempera- 

 ture and the great body of descending water, which 

 informs them their road is clear, and also by the 

 non-necessity of their remaining longer in the sea. 



