of the Fishery Board for Scotland. 



ing water attains very great momentum. Except in low conditions of 

 water, it would be impossible for salmon to swim through the foaming 

 race in the pass, and din ing these conditions the water covering the flat 

 surface of the apron is not more than ankle deep, thus entirely depriving 

 fish of a " take-off." On the left side of the dyke a slight angle in the 

 masonry and upper sill exists, and I am informed by the keeper, who has 

 for a number of years carried on the net fishing in the neighbourhood, 

 that when the river rises, and fish begin to run, the ascent is made at 

 this slight angle. The length of the apron from the foot of the pass I 

 found to be 124 feet. Immediately beyond the apron, which ends quite 

 abruptly, the water is very deep. Fish attempting to ascend the 

 Mugiemoss dyke have therefore to come to the surface at the lower end 

 of the apron, to traverse the shallow water on top of the apron, and 

 then from this almost impossible position to attempt the very difficult 

 ascent of the weir. 



In order to give facilities for fish to ascend, it is necessary, in my 

 opinion, to give them deep water on the surface of the present apron. 

 Three subsidiary dykes of 3 feet, 4 feet, and 5 feet height, built transversely 

 across the line of water flow, parallel to each other, would accomplish 

 this end, and would also flood the present pass sufficiently to afford 

 salmon an easy entrance to the upper river. It is necessary that the 

 lowest subsidiary dyke be placed at the extreme end of the apron, so as 

 to allow fish the benefit of the deep pool in jumping the dyke. A depres- 

 sion in the centre of this dyke 6 in. deep by 5 feet broad might be allowed. 

 1 would suggest that from this point the other two dykes should be 

 erected 30 feet up stream and GO feet up stream. A pool-pass of this 

 kind takes advantage of all the water of the river, and fish are enabled 

 to ascend in the main channel without great effort. 



About half a mile above Mugiemoss, Messrs. Pirie's Waterton works 

 and Stoneywood works — paper mills — occur. The works are in the 

 same enclosure and are of great extent, having been recently much 

 enlarged ; but two separate dykes and lades exist. The Stoneywood lade, 

 an immense and substantial structure, is conducted in an aqueduct above 

 the other. The two lades unite before the contained water is returned 

 to the river, and the breadth of the united tail-lade is apparently as 

 great as the breadth of the channel of the Don. This matter is referred 

 to by Mr. Young in page 22 of the First Annual Eeport. No change for 

 the better seems to have transpired since his report in 1882. 



The Waterton dyke is comparatively low and a gap exists in the 

 centre of it. Owing to the rough nature of the river bed immediately 

 below, the position of the pass does not seem to be well selected. Perhaps 

 the simplest plan here would be to insert a "diagonal " pass on the face 

 of the dyke from the extreme left, where some rocks project. The 

 "diagonal " to project downwards and outwards for a distance of about 

 10 feet, so that the foot of it rests upon the lower margin of the dyke, 

 Such a " diagonal " is most readily formed of 3-inch wood against iron 

 uprights driven into the face of the dyke. The chief trouble in this 

 locality, however, seems to be the abstraction of water, which during the 

 summer months, and when the water is low, renders the main channel 

 below the dam so dry that fish have not sufficient water in which to 

 ascend. 



Stoneywood dyke, the seventh artificial obstruction, has a long easy 

 gradient and is not high. The river bed immediately below is broad and 

 shallow, however, the latter by reason of the amount of water abstracted 

 by the great lade supplied by the dyke, and I am readily led to suppose 

 that during low levels of the river fish cannot reach the dyke. A fish- 

 pass exists which is, in my opinion, suitable for the purpose intended 



