of the Fishery Board for Scotland. 



327 



On the 18th December, a collection of 410 herrings varied in size 

 from 110mm. to 165mm. (4| to 6| inches), the range being thus 56mm. 

 The mean was 137mm., the average 137*5mm., and the mode 141mm. 

 (a little over 5j inches). An examination of the millimetre table, or of 

 the curve (PI. XVII.) shows that there is in this case a slight fusion of 

 two groups, and that the beginning of the large group is probably about 

 libera. The 2-millimetre arrangement of the measurements is as 

 follows — 



1 09-110 111-2 113-4 115-G 117 3 119-20 121-2 123-4 



I 3135 89 17 



At the end of the series the 2-millimetre arrangement is this : — 



150-1 152-3 154-5 156-7 158-9 160 1 162-3 164-5 



II 12" 3 4 3 — 1 - t 



the mode being 141mm., the mean 137-5mm., and the computed average 

 135*9mm. The mode (5 T 9 g- inches) probably best represents the group. 

 These herrings are spring herrings about 2 years and 8 or 9 months 

 old ; those taken on the 17th appear to be the autumn series, about 2 

 years and 3 or 4 months old. On the 29th December, 16 herrings were 

 taken, from 108mm. to 154mm. 



A series of older herrings than these were caught in Aberdeen Bay in 

 May and June, 1901 and 1903. 



On the 30th May, 1901, the collection numbered 601, ranging from 

 1 42mm. to 228mm. ; and forming two series at least. The first contained 

 598 herrings, from 142mm. to 186mm. (5 J to 7| inches), or it might be 

 182mm. The modal size was 159mm. or 160mm., the mean 164mm., 

 and the computed average 162mm., or 6^ inches. These herrings are 

 in their fourth year, and, judging from their position in relation to 

 other series on the synthetic table, they are spring herrings, and thus a 

 little over three years old . 



There were other three herrings, measuring respectively 196mm., 

 207mm., and 228mm. (9 inches). 



Two collections were obtained in June. The first, on the 13th (1 903), 

 contained 557 herrings, and three series were present. The curve 

 (PI. XVII.) and the millimetre table show that the first great group is 

 not pure, but is slightly mixed with the next group of larger herrings, 

 represented on 30th May and on 28th June, and the measurements ex- 

 tend from 118mm. to 182mm., a range of 64mm., which is too large. 

 The first series begins at 118mm., and apparently extends to 163mm. 

 (4-| to 6 inches), but it might go to 167mm. The 2mm. arrangement of 

 the measurements at this part is as follows: — 



156-7 158-9 160-1 162-3 164-5 166-7 168-9 170- 1 

 19 17 13 6 9 4 6 5 



The modal size of the group is 138mm. or 139mm. (5| inches), the mean 

 is 140*5mm., and the computed average 14r8mm., or 5| inches. This 

 group is thus about 2cm. (f inch) less than the group on 30th May, and 

 I take it to represent autumn herrings in the fourth year, that is, which 

 want about three months of being three years old. The group of 405 

 spring herrings, taken in Aberdeen Bay on 18th December, above 

 referred to, were of about the same age (2 years and 9 months) and of 

 the same size as these. 



The spring herrings mixed with them number about 30, and range 

 from about 164mm. to 182mm. There were also four herrings measur- 

 ing 208mm., 223mm., 225mm., 234mm. 



On the 28th June, fifteen days later, but in 1901, 650 herrings were 

 taken at Lunan Bay, a little further down the coast, in 12 \ fathoms. 



