310 



ON AN EXPEEIMENT IN THE KEEPING OF SALMON 



occasion (November 26th) seven of the females were weighed after 

 spawning, with the following results : — 



(a) 



(c) 

 (d) 



(e) 

 if) 

 (9) 



These give an average of 1 lb. 6 oz. nearly. The weights cannot 

 be compared individually with those taken before spawning, since 

 to obviate as far as possible excessive physical strain on the fish the 

 weights before and after spawning were not taken in any definite 

 sequence. If, however, the average weight 1 lb. 6 oz. be compared 

 with that of the twelve mature females enumerated in the first list 

 (thus omitting No. 1 for obvious reasons), namely 1 lb. 8-5 oz., the 

 average weight of spawn removed works out at 2ioz., or 10*2 per cent 

 of the average weight of fish. Assviming, on the other hand, that 

 the females spawned were the seven heaviest of the mature females 

 in the first list, then the latter give an average weight of 1 lb. 10| oz., 

 and the highest possible average weight of spawn removed would 

 thus be 4 J oz., or 17 per cent of the average weight of fish. 



On November 15th, 1907, i.e. at the time of the second spawning, 

 the weights were again taken of seven fish, of which the females were 

 weighed both before and after spawning. These were as follows : — 



Males 



(1) 

 (2) 



2 lb. 8 oz. 



9 R 



Females (1). Before spawning, 21b. 10 oz. After spawning, lib. 14 oz. 



(2) 2 10 1 12 



(3) , 2 „ 12 „ „ 1 „ 14 „ 



(4) ,) ^ }) ,, ,, -I ,, 4 ,, 

 i'^) )) 3 ,, ,, ,, 2 ,, -J ,, 



The average weight of these five females at this date is therefore 

 2 lb. 12"8 oz., while the average weight of spawn removed from them is 

 13*2 oz. This weight of spawn thus constitutes as much as 29'5 per 

 cent of the average total weight, and amounts in one individual (No. 2) 

 to one-third of the total weight of the fish. On June 19th, 1908, four 

 of the salmon were weighed and measured as representing an average 

 sample of the twelve that remained at the Laboratory. The figures 

 obtained were : — 



