78 ANNALS OF SCOTTISH NATURAL HISTORY 



limestone bed of the Alt Smoo above, and free access to 

 nearly 3 more miles of water? I think so, and in further 

 notes I have to offer I think I can prove that this coloration 

 in fishes is dependent upon light to a very large extent ; 

 dependent also upon the colour of the water and bottom, in 

 and on which they feed ; though we believe there are other 

 causes besides, which appear to be more obscure to our senses 

 at present. 



When I come to consider some of the other lakes and 

 streams, the object of dwelling upon these peculiarities of the 

 Alt Smoo trout may become more apparent. 



CRASSPUIL TROUT. 



I will now speak of another loch in the Durness district 

 viz. Loch Crasspuil. This loch contains most lovely 

 trout, perhaps more closely allied to Loch Leven trout both 

 as regards appearance and in the number of the csecal 

 appendages, as well as in the flavour of their flesh. The 

 natives look upon them, indeed, as a cross between sea-trout 

 and burn-trout, having silvery scales and growing to a large 

 size. This loch is united to the sea by a shallow stream, 

 and there is every reason to believe that these trout were 

 at one time migratory, but are now confined ; the most of 

 the burn water being diverted, and a sluice put on to supply 

 and regulate water to a mill-wheel at Balnakeil. 



On the i 3th June 1882, having obtained the minister's 

 coble, my man and I endeavoured to obtain samples of 

 these fish. At first they rose very freely, but I was dis- 

 appointed with the size, none which were caught being up to 

 the -|- lb., and the lot perhaps averaging \ Ib. They were 

 wonderfully silvery : belly shiny white, covered with minute 

 silvery scales ; back very clear green ; and sides spotted 

 with small dark spots, all being covered with the lovely clear 

 scales. The silvery colour is easily accounted for. The water 

 of the loch is clear and bright green, or dark green, according 

 to the depth, over a bottom of pure white or light yellow sand. 

 The green of the trout's back follows the green of the water, 

 the silvery white the colour of the bottom. The spawning- 

 ground is good, not wide, but nearly a mile long, and runs 



