of the Fishery Board for Scotland. 



9 



APPENDIX I. 



SALMON PASSES. 

 By W. L. Calderwood. 



From early times salmon fishery legislation has provided, inter alia, 

 for the distribution of fish in upper waters, and has decreed that gaps and 

 passes be provided in obstructions. 



The obstructions to the ascent of salmon may be either natural waterfalls 

 or artificial weirs and dam dykes. In a few cases a combination of these two 

 types exists, natural barriers of rock having been levelled up by super- 

 imposed building. The owner of an artificial obstruction in a salmon river 

 is required, under the general Scottish Salmon Acts, to provide a salmon 

 pass; while either artificial or natural obstructions may be purchased by a 

 District Fishery Board for the purpose of removal or, in the case of a 

 waterfall, for the purpose of erecting a fish pass. Agreement on the part 

 of the owner is, however, required in the latter case. It is unnecessary, 

 and it would be unwise, to speculate what may be deemed proper in 

 future legislation, but undoubtedly the benefit of opening up all available 

 spawning grounds is more and more realised as our salmon fisheries 

 continue to increase in value. 



Amongst the earliest artificial obstructions were the cruive dykes or 

 fishing weirs which once were so numerous in Scotland, but which now, 

 fortunately, are to be found only in a few rivers. The gap in the cruive 

 dyke — called also the " mid-stream " — was at one time required to be of 

 such size " as a swine of 3 yer elde, well fed, is of length so that neither 

 " the grouzie nor the tail may wyn till any side." In process of time the 

 rule has become more observed in the breach than the observance, or, in 

 other words, the rule requiring the breach has not been observed. Ulti- 

 mately the Courts held that the rule had fallen into disuetude ; but this 

 seems to have happened simply because witnesses could not point to any 

 cruive which retained a mid-stream, being in ignorance, presumably, of 

 the Inverawe cruive, which, with its ample mid-stream, has existed in its 

 present form since about 1480, in the reign of James III. of Scotland. 



I desire in the present instance to describe what I regard as the important 

 features in salmon passes, since it seems to be from the study of the funda- 

 mental principles, and how they may be applied, that we are most likely to 

 arrive at really or approximately satisfactory arrangements. I have seen all 

 the passes in Scotland, and I have seen many of them on several occasions. 

 I do not hesitate to say that the majority of them are unsatisfactory. 

 Some useful purpose will therefore, I hope, be served by an attempt to 

 distinguish the valuable from the useless or harmful features, and by 

 showing how the valuable features may be applied. 



One has at the outset to state that obstructions are clearly so very 

 different that it is necessary to consider carefully the precise conditions of 

 each. Weirs have, no doubt, certain features in common — the height is 

 well defined, the sill is more or less uniform, the water above is almost 

 invariably smooth ; yet the down-stream face may be gently sloping, or it 



