THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY, 



[SECOND SERIES.] 

 No. 28. APRIL 1850. 



XXII. — Notes on the Salmon and Bull-trout, 

 By John Blackwall, F.L.S. 



In a short paper on the Salmon, Salmo salar, published in the 

 ( Annals and Magazine of Natural History/ vol. xi. p. 409, I 

 have endeavoured, on physiological principles, to establish the 

 fact, that the growth of that valuable fish is not by any means so 

 rapid as it is commonly supposed to be by ichthyologists. Ob- 

 servations having relation to this subject and also to the oeconomy 

 of the bull-trout, Salmo eriox, have been continued to be made, 

 as suitable occasions presented themselves, up to the present 

 period, on a plan similar to that previously adopted, and I am 

 induced to insist upon the decided advantage which a recourse 

 to physiological phenomena possesses in investigations of this 

 kind over the customary practice of mechanically marking fish 

 as objects of experiment, in consequence of the various sources 

 of error to which the latter mode of proceeding is exposed. 



Persons, in their endeavours to determine the rate of growth 

 in fish by marking specimens, too frequently employ subordinate 

 agents to carry their intentions into effect, to whom not only 

 their system of marks is of necessity made known, but the anti- 

 cipated result is also communicated. Now should it so happen 

 that the agents are dependent upon their employers, or in any 

 respect interested in making the event appear to coincide with 

 their preconceived opinions, the desired object may be easily 

 attained either by secretly marking specimens of a larger size 

 than those which they were instructed and perhaps observed to 

 select for the purpose, and by exhibiting them alone when re- 

 captured, or by adapting the marks to fish subsequently taken, 

 whose dimensions appear to be best suited to promote the end 

 they have in view. Besides, it often happens that all the par- 

 ticulars of the undertaking transpire, and becoming widely cir- 

 culated, other parties resident in the neighbourhood may apply 

 similar marks to fish of different sizes captured in the same 



Ann. $ Mag. N. Hist. Ser. 2. Vol. v. 16 



