244 Mr. J. Blackwall on the Salmon and Bull-trout. 



On the 12th of November 1844, a salmon was captured 

 weighing fifteen pounds, the weight of the lobes of roe, which 

 contained a large quantity of ova in an advanced state of deve- 

 lopment, being two pounds and three-quarters. 



A salmon captured on the 13th of November 1844 weighed 

 seven pounds and a half, and the weight of the lobes of roe, 

 which comprised ova almost in a fit state to be deposited, was 

 two pounds. 



A bull-trout taken on the 18th of November 1844 weighed 

 five pounds and a half, the weight of the lobes of roe, which 

 contained ova in an advanced state of development, being one 

 pound and a quarter. 



On the 11th of October 1847, a bull-trout weighing half a 

 pound was captured, whose lobes of roe, comprising ova nearly- 

 ready for deposition, weighed two ounces. 



A salmon weighing fifteen pounds and a half was taken on the 

 22nd of October 1847, and the lobes of roe, which contained ova 

 in an advanced state of development, weighed three pounds. 



The lobes of roe, comprising highly developed ova, taken from 

 a salmon weighing twenty pounds, which was captured on the 

 10th of November 1847, weighed three pounds and fourteen 

 ounces. 



Took the lobes of roe, containing ova on the point of being 

 deposited, from a salmon weighing sixteen pounds, which was 

 captured on the 26th of November 1847, and found their weight 

 to be four pounds. 



From these instances it is apparent that the weight of salmon 

 and bull-trout may be diminished one-fourth by the emission of 

 their ova alone, the weight of the collapsed ovaries with their in- 

 cluded germs being too insignificant to be taken into considera- 

 tion; and if to this cause of decreased ponderosity be added 

 another, namely deterioration in condition during the sojourn of 

 these species in fresh water, the absolute loss in weight may be 

 estimated at one-third or more, a circumstance which ought on 

 no account to be overlooked in attempts to determine their rate 

 of growth by marking individuals ; and this remark applies with 

 peculiar force when the subjects selected for experiment are kelts, 

 as, unfortunately, it is too commonly the practice to omit mea- 

 surement altogether on such occasions and merely to give a 

 statement of weight, which, unaccompanied by other data, is 

 evidently insufficient to decide the point in question. 



In drawing up this paper I have purposely avoided applying 

 the Scotch term grilse to young salmon which have not spawned, 

 as I entertain the opinion that few appellations employed by 

 ichthyologists have been more abused or have led to greater con- 

 fusion and misapprehension than this. 



