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XXVII. — On the Effect of Temperature on the taking of Salmon with Rod and Fly in 

 the River Spey at Gordon Castle in the Autumns of 1898, 1899, 1900, and 1901. 

 By George Muirhead, Commissioner for His Grace the Duke of Richmond and 

 Gordon, K.G. (With Four Plates.) 



(MS. received April -lb, 1903. Read June 1, 1903. Issued separately September 12, 1903.) 



The Duke of Richmond and Gordon's salmon fishings on the Spey extend on both 

 sides of the river from the Boat o' Brig, where the Highland Railway crosses the stream 

 between Keith and Elgin, to the sea, a distance of about nine miles. 



The river here varies in breadth from 50 to 140 yards, and in depth from 2 feet, 

 where the stream is broad, to about 10 or 12 in some of the pools. Its course is rapid, 

 the fall being about 1 6 feet to the mile, and its volume is quickly increased when there 

 is much rain, or when snow melts in the Monadhliadh and Grampian Mountains. 



There are many excellent pools for salmon fishing with the rod on the Gordon Castle 

 water, and in them large numbers of fish are usually taken with the fly every year 

 during the month of September and the first half of October. 



His Grace's guests at Gordon Castle fish for salmon in the Spey there with rod and 

 fly only, no other lure than the fly being used. They are all well-known and skilful 

 salmon fishers, who generally visit Gordon Castle during the salmon rod-fishing season 

 every year, and in the autumns of 1899 and 1900 they included His Royal Highness 

 the Prince of Wales. The pools which are fished, and the arrangements connected with 

 the fishing, were the same in each of the four seasons above mentioned. 



The usual experience of salmon fishers with rod and fly is, that whilst the fish may 

 take well on certain days, yet, on other days, which do not appear to differ from 

 these in any way whatever, they can scarcely be induced to rise to it. This peculiarity 

 was particularly observable in the Gordon Castle water in the autumn of 1897 ; and as 

 it then occurred to me that the cause of it might be on account of changes in the 

 temperature of the water from day to day, I made careful observations of the tempera- 

 ture of the river during the rod-fishing season in the four following years. 



The temperature of the water in the Spey was taken twice a day near Gordon Castle 

 at nine o'clock in the morning and four o'clock in the afternoon, being the most con- 

 venient hours for ascertaining approximately the lowest and the highest temperatures 

 for the day, and the results are indicated by the dark blue line on the Diagrams. The 

 red line shows the daily mean temperature of the air at the station of the Scottish 

 Meteorological Society at Gordon Castle during the same period. The red columns 

 indicate by their respective heights and the figures marked immediately above each of 

 them the average number of salmon which were caught by each ' rod ' daily during the 



TRANS. ROY. SOC. EDIN., VOL. XL. PART III. (NO. 27). 5 h 



