328 Part III. — Eighteenth Annual Report 



one female was ripe and three females were spent, while the remainder were 

 unripe (or, in the case of the males, possibly spent). Of the 207 specimens 

 caught off Aberdeen in the latter half of August and first half of Sep- 

 tember 95 were females, and of these 84 were spent ; nine were ripe. The 

 males were either unripe or spent. In October, 12 fish were sent from 

 Kilbrennan Sound; of these, five were spent females. It is to be inferred, 

 then, that on the West Coast spawning takes place in July and part of 

 August. The lower and upper limits of the spawning season it is so far 

 not possible to fix. The mackerel caught off Aberdeen had ceased 

 spawning by the middle of August. The smallest ripe male was 27*7cm. 

 in length ; the smallest ripe female was 28'9cm. long. The smallest ripe 

 male and ripe female mackerel recorded by Cunningham* were 30*3 and 

 29 '5cm. long respectively. He considered that this form had a short 

 spawning period in the vicinity of Plymouth — viz., from the middle of 

 May to the end of July. 



Weights of Ripe and Unripe Mackerel. 



The accompanying Table (XV.) gives some particulars of the weight 

 of ripe and unripe mackerel at various sizes. The average weight is 

 given for all the mackerel at each size, the number of specimens from 

 which the average is made being indicated by a number within brackets. 

 In most instances the average weight of the unripe male exceeds that of 

 the ripe male. In two cases— viz., at 32 and 35cm. — the ripe male exceeds 

 the unripe by 10 and 7 grammes respectively. At 33cm. the unripe 

 male exceeds the ripe by 39 grammes. There is much greater variation in 

 the relation of the ripe and unripe females to one another. Cunningham 

 records a ripe male of 42 # 5cm. length weighing 524 grammes; the 

 only ripe male of this size which I have weighed was 837 grammes in 

 weight. The numbers, which are given in Table XV., are not sufficient to 

 permit of any detailed discussion. It is, however, very evident that, so 

 far as they go, they point out, in several cases, that the ripe and unripe 

 males are of very similar weight, and so with the ripe and unripe females, 

 while in other instances they diverge considerably. 



* Loc. cit. 



[Table. 



