On the Growth of the Salmon. 375 



1843, January 9. — Dr Abercrombie, Vice-President, in 

 the Chair. 

 1. On the Growth of the Salmon. By Mr Andrew Young, In- 

 vershin, Sutherlandshire. Communicatedby James Wilson, 

 Esq. 



Mr Young has here taken up the subject of the salmon's growth 

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

 earliest or fresh-water 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 grilse, and shews by tabular lists (the result of frequently 

 repeated experiments), that the increase in their dimensions is ex- 

 traordinary 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 de- 

 scending smolts, by making a peculiar perforation in the caudal fin, 

 by means of small nipping irons constructed for the purpose. He 

 re-captured a considerable 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 diff'er- 

 ence in the length of their sojourn in the sea. Again, in April and 

 May of 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 returning up the river, and bearing' his peculiar 

 mark, — ^the adipose fin being absent. Two of these specimens were 

 exhibited to the Society. One marked in April, and re-captured on 

 the 25th of July, weighed 7 lb. ; the other, marked in May and re- 

 captured on the 30th July, weighed 3^ lb. As the season advances 

 grilse increase in size, those being the largest which 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 shewing the transition of grilse into salmon. He marked 

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

 to re-descend into the sea. He re-captured them in the course of 

 the ensuing summer as finely-formed salmon, ranging in weight from 

 9 to 14 lb., the difference still depending on the length of their 

 sojourn in the sea. He has tried these experiments for many sea- 

 sons, but never twice with the same mark. A specimen marked as 

 a grilse of 4 lb. in January 1842, and re-captured as a salmon of 

 9 lb. in July, was exhibited to the Society. It bore a peculiarly 

 twisted piece of rnppe}- wire in the upper lobe of the caudal fin.. 



