Royal Society of Edinburgh. 157 



ROYAL SOCIETY OF EDINBURGH. 

 Januarj' 9, 1843. — The following communications were read: — 

 1. " On the Growth of the Salmon ;" by Mr. John Young, Suther- 

 landshire. 



Mr. Young has here taken up the subject of the Salmon's grow^th 

 where it was necessarily left otF by Mr. Shaw. So far as the earliest 

 or freshwater state of the fish is concerned, he entirely agrees with 

 the observer just named. He then states the various opinions which 

 prevail regarding the more or less rapid growth of smolts and gi'ilse, 

 and shows by tabular lists (the result of frequently repeated experi- 

 ments) that the increase in their dimensions is extraordinary so soon 

 as they descend into the salt water. So far back as the months of 

 April and May 1837, he marked a number of descending smolts, by 

 making a peculiar perforation in the caudal fin by means of small 

 nipping-irons constructed for the purpose. He recaptured a consi- 

 derable number of them ascending the rivers as grilse in the course 

 of the ensuing months of June and July, and weighing several pounds 

 each more or less, according to the difference in the length of their 

 sojourn in the sea. Again, in April and May 1842 he marked a 

 number of descending smolts by clipping off the little adipose fin 

 upon the back. In June and July he caught several of them return- 

 ing up the river and bearing his peculiar mark, the adipose fin being 

 absent. Two or three specimens were exhibited to the Society. One 

 marked in April and recaptured on the 25th of July w'eighed 7 lbs., 

 the other marked in May and recaptured on the 30th of July weighed 

 3| lbs. As the season advances grilse increase in size, those being 

 the largest w^hich abide the longest in the sea ; they spawn in the 

 rivers after their first ascent, and before they have become adult 

 salmon. 



Mr. Young also described various experiments instituted with the 

 view of showing the transition of grilse into salmon. He marked 

 many small grilse after they had spawned in winter and were about 

 to redescend into the sea. He recaptured them in the course of the 

 ensuing summer as finely formed salmon, ranging in weight from 9 

 to 14 lbs., the difference still depending on the length of their so- 

 journ in the sea. He has tried these experiments for many seasons, 

 but never twice with the same mark. A specimen marked as a grilse 

 of 4 lbs. in January 1842, and recaptured as a salmon of 9 lbs. in 

 July, was exhibited to the Society : it bore a peculiarly twisted 

 piece of copper wire in the upper lobe of the caudal fin. Those 

 marked and retaken in 1841 were marked with brass wire in the 

 dorsal fin. With these and other precautions, Mr. Young debarred 

 the possibility of any mistake as to the lapse of time. Both grilse 

 and salmon return uniformly to their native streams ; at least it very 

 rarely happens that a fish bearing a particular mark is found, except 

 in the river where it was so marked. Salmon in the perfect state as 

 to form and aspect also increase rapidly in their dimensions on again 

 reaching the sea. A spawned salmon weighing 12 lbs. was marked 

 on the 4th of March, and was recaptured on its return from the sea 

 on the 10th of July, weighing 18 lbs. Mr. Young is of opinion that 



