of the Fishery Board for Scotland. 



63 



three years. Every season we obtain more data from the marking of 

 kelts, especially those of Tay fish, whose scales are examined. In each 

 instance this mark is distinctly visible, and in none of the numerous ex- 

 amples is it absent. As these fish were all marked in the kelt stage 

 they must have spawned, and when we find this distinguishing feature 

 on their scales and not on those of some other salmon, we may reasonably 

 conclude that the latter have not spawned, at least within recent years. 

 This, though satisfactory to the student of scales, is not the only evidence 

 we have to trust to. The ''wired" smolts that returned in the year 

 after marking were undoubtedly maiden fish, and come under the some- 

 what misleading name of grilse. It was impossible for the small spring 

 salmon to spawn as grilse in the winter of 1 906, and again return as clean 

 fish by February 1907, and the same remark applies to the young sum- 

 mer fish captured in April and early in May. In all the Tay marking 

 there is no instance of a fish returning in the clean condition earlier 

 than the July after its descent as a kelt. This argument will not, how- 

 ever, apply to the "wired" smolts of 1905 which were retaken in July 

 and August 1907, one of which weighed 27 lbs., representing a growth of 

 about a pound per month while absent from the river, and its scales 

 bore no Spawning-mark. The growth of this fish is very noticeable, but 

 would be still more remarkable could we admit that the scales were not 

 to be depended on and that it might have spawned. Were this the case, 

 it must have spawned as a grilse toward the end of 1906, and the pro- 

 cess naturally entails a considerable loss of weight, which would have to 

 be recovered on the salmon's return to the sea. It also implies an ab- 

 stention from food during the time the fish was absent from the marine 

 feeding grounds, so that, on the hypothesis that the fish had spawned 

 and was not on its first return, we would have to account for a greatly 

 increased power of assimilation, exercised over a shorter period than 

 twenty-seven months. 



Reverting to the young summer fish, we find that the recaptures in 

 April and May after two years of sea feeding had developed scales such as 

 we would expect, with two annual rings (outside the parr markings), sur- 

 rounded by 4 to 8 lines of the third summer's growth, and no trace of a 

 Spawning mark. Allowing that as smolts they were 2| years old, their 

 age on recapture would be about 4| years. 



The autumn salmon form the next group, and here we notice the 

 longer sea feeding of the third summer exhibits 8 to 16 lines outside the 

 second annual ring. Their age is about 4| years. It may be asked why 

 a distinction is made between summer and autumn fish, when both are 

 nearly the same age and differ little in the number of lines of their third 

 summer's feeding ; but the reason is that the summer salmon are gener- 

 ally of a lighter weight than those arriving a few months later, and there 

 are differences in their scales which point to their life-history being 

 dissimilar, and indicate the need of further investigation regarding their 

 antecedents. The 27-pounder of the autumn class has already been men- 

 tioned. It was a male, and probably had grown more rapidly than a 

 female would have done. At least this seems the rule with spring fish, 

 as would appear from an analysis I have made of the weights of a con- 

 siderable number of both sexes, selecting those only which the scales 

 showed to be maiden fish rising five years old, and I find that over a 

 series of years the males averaged 22| lbs. while the females averaged 

 17^ lbs. These were caught by the rod in the upper Tay, and when the 

 sex was at all doubtful, it was determined by dissection. 



It may not be out of place to mention that there are nearly three 

 females to one male in the case of the spring fish referred to, whereas 

 among summer fish which I have recorded, males are much more numerous 



