MR YOUNG ON THE GROWTH OF GRILSE AND SALMON. 345 



fresh to salt ; and in proof of this I may refer to the following fact, that, with the 

 exception of the early state of parr, in which the growth is admitted to be slow, 

 salmon actually never do grow in fresh water at all, either as grilse, or in the 

 adult state. All their growth in these two most important later stages takes 

 place during their sojourn in the sea. Not only is this the case, but I have also 

 ascertained that they actually decrease in dimensions after entering the river, and 

 that the higher they ascend the more they deteriorate, both in weight and quality. 

 In corroboration of this I may refer to the extensive fisheries of the Duke of 

 Sutherland, where the fish of each station of the same river are kept distinct from 

 those of another station, and where we have had ample proof that salmon habi- 

 tually decrease in weight in proportion to their time and distance from the sea. 



I have also instituted another series of experiments for the purpose of shew- 

 ing the relationship of the grilse and adult salmon, and connecting, as it were, 

 these two final stages with each other. In the spring of 1841 I marked a number 

 of spawned grilses soon after the termination of the spawning season. I took a 

 net and coble, and fished the rivers for the purpose ; and all the spawned grilse of 

 4 Ib. weight were marked, by putting a peculiarly twisted piece of wire through 

 the back fin. They were immediately thrown into the river, and of course disap- 

 peared, making their way downwards with the other spawned fishes to the sea. 

 In the course of the next summer we again caught several of these fish which we 

 had thus marked with wire as 4 Ib. grilse, grown, in the short period of four or five 

 months, into beautiful full-formed salmon, ranging from 9 Ib. to 14 Ib. in weight, 

 the difference still depending on the length of their sojourn in the sea. 



Again, in January 1842, I repeated the same process of marking 4 Ib. grilses 

 which had spawned, and were therefore about to seek the sea ; but, instead of 

 placing the wire in the back fin, I this year put it in the upper lobe of the tail or 

 caudal fin. On their return from the sea we caught them, salmon as before. 

 Two of these fish, marked as grilse on the 29th of January, and weighing at that 

 time 4 Ib., were caught as salmon on the 4th and 14th of July, weighing respec- 

 tively 8 Ib. and 9 Ib. They were transmitted, at your request, to the care of Mr 

 GOODSIE of the College of Surgeons, for preservation by that gentleman, in whose 

 hands they may now be seen, in confirmation of my statements on the subject of 

 the salmon's growth.* 



I may here state, that the motive which first induced me to mark both grilse 

 and salmon was the desire to ascertain whether the fish of a river were a breed 

 peculiar to that river alone ; that is, whether the same individuals, after descend- 

 ing to the sea, returned to their original spawning grounds, or whether, as many 

 supposed, the main body returning shorewards from their feeding grounds in dis- 

 tant parts of the ocean, and progressing southwards along the coasts of Scotland, 

 were thrown into, or encouraged to enter, estuaries and rivers by various acci- 

 dental circumstances, and thus, that the numbers obtained in these estuaries and 



* The specimens above referred to are now in the Museum of the Royal Society. 



