410 Mr. J. BlackwalPs Notes on the Salmon. 



Young, given in the e Annals and Magazine of Natural History/ 

 vol. xi. p. 157, induced me once more to turn to them, under the 

 impression that they comprised evidence in favour of a conclusion 

 opposed to that arrived at by the latter observer. 



Concurring with Mr. Shaw as regards the history of the sal- 

 mon from its rupturing the external capsule of the egg to the pe- 

 riod when it acquires the migratory dress and descends to the sea, 

 Mr. Young has endeavoured to determine, by observations made 

 upon marked individuals, the growth of this species after its first 

 arrival in the salt water. 



In the months of April and May 1837, he marked a consider- 

 able number of descending smolts by making a peculiar perfora- 

 tion in the caudal fin by means of small nipping-irons ; in the 

 course of the ensuing months of June and July many of them 

 were recaptured ascending the river as grilse, and weighing se- 

 veral pounds each, more or less, according to the difference in the 

 length of their sojourn in the sea. Again, he marked a number 

 of descending smolts in April and May 1842, by clipping off the 

 adipose fin, and in June and July he caught some of them return- 

 ing up the river, the adipose fin being absent. One of these spe- 

 cimens, marked in April and recaptured on the 25th of July, 

 weighed seven pounds, and another, marked in May and recap- 

 tured on the 30th of July, weighed three pounds and a half. 



Many small grilse, marked after they had spawned in winter 

 and were about to redescend into the sea, in the course of the en- 

 suing summer were recaptured as finely formed salmon, ranging 

 from nine to fourteen pounds in weight, the difference still de- 

 pending upon the length of their sojourn in the sea. A specimen 

 marked as a grilse of four pounds in January 1842, was recaptured 

 as a salmon of nine pounds in July. 



A salmon which had spawned, weighing twelve pounds, was 

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

 from the sea on the 10th of July, weighing eighteen pounds. 



Such are the experiments detailed in the report of Mr. Young's 

 paper, and the inference deduced from them and others of a si- 

 milar kind is that the growth of the salmon in its transition from 

 a smolt to a grilse, from a grilse to the perfect state as to form 

 and aspect, and also in the perfect state, is extraordinarily rapid 

 during those portions of its existence which are passed in the sea, 

 but Mr. Young entertains the opinion that salmon rather dimi- 

 nish than increase while they remain in fresh water. 



Now, though it is an undoubted fact that great deterioration 

 in the condition and, consequently, in the weight of salmon uni- 

 formly takes place while they are engaged in perpetuating their 

 species, yet that the growth of young individuals which do not 

 accompany their congeners to the sea is steadily progressive, ob- 



