n 



152 NORTHERN ZOOLOGY. 



" The growth of the fry is very rapid. On the 20th of April the rivers were 

 full of salmon-smoults, varying from six to nine inches, having attained that length 

 in about three weeks. They were in the finest possible condition, covered with 

 small silvery scales, differing in shape from those of the trout or par. They are 

 very tender, and constantly die a short time after being touched. During the 

 months of March, April, and May, the rivers abound with kelts, or spawned sal- 

 mon, descending towards the ocean, and smoults, or fry, pursuing the same course." 

 Dr. Knox, in the appendix to the able paper from which the foregoing passages 

 are abridged, remarks that there are two circumstances which persons of sound 

 judgment and great experience with regard to the salmon question still think un- 

 decided, or at least demanding a more extended proof. The first is a series of 

 experiments to determine the growth of salmon-fry from the state of the egg to its 

 attaining the length of six, seven, eight, or nine inches, before which it is seldom 

 seen by the angler, and after which it ceases to be found in fresh-water rivers ; 

 secondly, proof that the fish we call salmon-fry, taken in salmon-rivers by angling 

 during the months of April and May, do really proceed to the ocean and return 

 after a period to the rivers as grilse, Salmon-trout*, and salmon. The facts 

 ascertained by Dr. Knox, in conjunction with the previous observations of others who 

 have attended to the subject, go towards the answer of the first question ; and the 

 following extract from Sir William Jardine's paper may be considered as a reply 

 to the second. " It has always been a subject of dispute whether the fry returned 

 to the rivers as grilse in the same season in which they descended. I have had no 

 doubt of this for several years, but it was very difficult to prove. In the Tweed I 

 have killed grilse early in the season, so small as to weigh only two pounds, and 

 seen them gradually increase in size as the season advanced ; the intermediate size, 

 however, between the fry and the two pound grilse was wanting. During the two 

 years which the fisheries of Sutherland have been in the possession of the Duke, a 

 set of experiments have been instituted by his factors, one of which leaves no doubt 

 upon the subject. Last spring, several thousands of the fry were marked in the 

 different rivers, among others by Mr. Baigrie, in the Laxford and Dinard, on the 

 west coast. In the Laxford, the first grilse (marked in April as fry) returned on 

 the 25th of June, and weighed three pounds and a half. Many others were got 

 during the season, from this weight to six pounds and a half, returning to the rivers 

 where the fry were marked, which was known by a particular mark being used in 

 each, and showing that a return to their breeding ground was as frequent, or rather 



* Dr. Knox considers our Salmon-trout to be merely a variety of the Safmo salar. 



