F. day: periods of migration. 



125 



July 



August 



September 



Salmon. 



233 

 113 



Grilse. 



371 



408 



154 



Trout. 

 254 

 164 

 1 29 



October ( 1 st half of) ... 71 ... 53 ... 186 

 Salmon ascend in every month of the year, in numbers com- 

 paratively not very unequal. Grilse, speaking roundly, do not 

 ascend in the first half of the year, and all but a fraction within two 

 consecutive months in the middle of the year; subsequently, their 

 ascent is checked. Forms ascending throughout the year being 

 adults ; those coming in shoals being the young of the same species. 

 That this is so, is further borne out by the trout column, wherein are 

 comprised both old and young, and in June they suddenly increase 

 by 300 per cent, and another 50 per cent, in July, during which 

 month a fourth of the whole of the year's captures were recorded, 

 while the average weight falls off during the months when the young 

 appear to be ascending. The increase in trout in October is due to 

 fishes ascending to spawn, when the average weight of the fish 

 increases. Russel has also shown that in examining some returns 

 of takes of grilse and salmon from the Tweed, he found that the 

 proportion which the grilse of any one year bore to the average 

 number of grilse, was found to have been just about the proportion 

 which the salmon of the following year bore to the average number 

 of salmon. Taking a series of years, the average weight of grilse 

 captured in the Tweed was found to be in June, 3 lbs. 11 J ozs. ; 

 July, 4 lbs. 5 J ozs.; August, 4 lbs. 15 ozs.; September, 5 lbs. 12 J ozs.; 

 October,. 6 lbs. nf ozs: the late comers having been longest in 

 the sea. 



During their migrations up river these fish have to overcome many 

 obstructions, whether natural obstacles or artificial impediments, as 

 weirs, and frequently these can only be surmounted during a heavy 

 flood. If the water in any river is very low, possibly the pools would 

 contain no safe resting places for ascending salmon, and spring fish 

 would be very unlikely to accomplish their ascent, for they would 

 most probably be captured by man or destroyed by vermin. 



Mr. Stephen deposed, before the Committee on the Salmon 

 Fisheries in 1824, that, 'Our cruives in the river Don are so constructed 

 that salmon of 10 lbs. weight can at all times go up, but none can 

 descend past the cruives. We fish generally in the pools above the 

 cruives, and if the unspawned salmon returned again down the river 

 we would undoubtedly catch them there, which is never the case. 

 They are never seen to descend the river, except as kelts, after having 

 spawned.' 



April 1886. 



