332 



Part III — Twenty-fourth Annual Report 



These spring herrings are live years of age, and they appear to be the 

 first annual series which attains maturity. 



The second group of herrings comprised 248 females and 282 males. 

 The beginning of the series is where the fusion with the younger series 

 occurs, at 251mm., but it probably extends back to about 23-5cm. 

 (9| inches), judging from the form of the curve. The place where it 

 ends is not so immediately clear. The following shows the arrangement 

 in 2mm. groups :— 



270 272 274 276 278 280 282 234 286 288 290 292 294 296 298 300 302 304 306 308 



Female, 11 7 11 f> 5 2 1 2 2 - 2 1 - - - 1 - 1 - - 



Male, - 14 11 7832244-1 - - - - - - 1 - -> 



25 18 18 13 8 4 3 6 6 - 3 1 - - - 1 - 2 - 



And the measurements under the millimetres are these: — 



276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 



Female, 3 2 4 1 2 1 1 - 2 1 1 - - 2 



Male, - 3 5 2 2 1 1 - 2 2 2 2 2 - - 1 - 



676332-3 2 433--3- 



It appears from this that the group terminates at 281mm. (llyg- 

 inches), the rest of the herrings belonging to, at least, one older group. 

 The modal size is 257mm. (10^ inches), the mean is 266mm. (or 261mm. 

 on the extension of the group back to 240mm.), and the average as com- 

 puted is 262 1mm. (10 T 5 6 inches). 



The males begin and end like the females, have exactly the same 

 modal size, while the computed size is 261mm. 



The group comprising both sexes contains 530 herrings, with the 

 same range, modes, and means, the computed average size being 261 -5mm. 

 These herrings are six years of age. 



The rest of the herrings numbered 10 females and 12 males: the 

 former ranged in size from 283mm. to 305mm. (11| to 12 inches), and 

 the latter practically the same, 283mm. to 304mm. These herrings are 

 seven years old, and although the range of size shown is only 22mm. 

 and 21 mm., it is probable, judging from the 2mm. table given above, that 

 the three herrings at about twelve inches (300mm., 304mm., 305mm.) 

 are at least a year older still. Growth in length, as is well known, is 

 much retarded when the fish attain to maturity and afterwards, as is 

 shown, indeed, by comparing the modal sizes of the two series under 

 discussion, the growth indicated in a year being only about 19mm. 

 (| inch). 



It will be noticed that in both series the males are more numerous 

 than the females, and that, while in the second or older series the size 

 of the males and females is the same, the males in the first group are 

 appreciably smaller than the females. In both lots of males of this 

 series measured, the mode in the *5cm. curves is at 23 5cm. ; in the 

 older group one of the modes is at 25*5cm.; and the other at 26cm. 

 When all the males are considered together, the mode in the '5cm. curve 

 is at 23 - 5cm. in the younger group and at 25'5cm. in the older group. 

 In the two lots of females, the cusp in one case in the younger group 

 was at 23-5cm., and in the other at 24*5cm. ; in the older group both 

 the cusps or modes were at 25'5cm. 



There was thus a greater number of small males than of small females 

 in the younger series, but this does not necessarily denote that the 

 male reaches maturity at a smaller size than the female. 



In March, another lot of these spring herrings from the Forth were 

 measured. They were forwarded to the laboratory, and placed in weak 

 formaline solution for a time ; they were measured by the laboratory 

 attendant, who also determined the sexes in most of them by opening 

 the fish ; doubtful cases were determined by myself. 



