of the Fishery Board for Scotland. 



323 



(b) The Annual Groups. 



In dealing with the numerous collections of larger herrings, it will 

 not be necessary to refer to them all in detail. The method T. adopted 

 in elucidating the rate of growth and the age of the herrings in the 

 various collections was as follows. After determining the rate of growth 

 and the sizes for the first and second year, I set down on a very large 

 and long sheet, divided into centimetre and millimetre squares, all the 

 other collections, showing the range of sizes and the average or modal 

 size, that is, the size at and around which the great bulk of the herrings 

 in a collection were aggregated. Very little consideration was required 

 to allot almost all the collections in a particular month to the proper 

 year, and in the accompanying Table I have represented the modal sizes 

 of the collections in this manner, and also in some cases (by a cross) the 

 sizes of individual herrings or small collections. 



There are a few general considerations that may be referred to. The 

 collections were in nearly every case made by means of a small-meshed 

 net fixed outside the cod-end of an ordinary large otter trawl, which was 

 dragged along the bottom for an hour and more. Several miles of 

 bottom were thus trawled over, and this is probably the explanation that 

 a mixture of herrings of different series occurs in a few of the collections. 

 In most instances this has not happened, the groups being very distinct; 

 but in some there are a few, or many, herrings either larger or smaller 

 than the limits of the series, and in one or two collections the spring and 

 autumn series seem to be more or less blended. They are referred 

 to below. 



The larger fully adult herrings are not well represented in the collec- 

 tions, probably from their more pelagic habitat. The small herrings in 

 their second year are also not very fully represented until the winter, 

 doubtless due to the fact that they were able to escape through the 

 meshes of the net. They are well shown, however, in the collections 

 made in the Firth of Forth by the Garland, with a fine-meshed shrimp- 

 trawl, and also in Lochfyne, as above described. 



In May certain collections of small herrings were obtained in the 

 Firth of Forth with the small -meshed net around the otter-trawl. On 

 the 9th, in from 7 to 11 fathoms, 161 were taken. The smallest was a 

 single herring measuring 71mm. (2|| inches), representing the herrings 

 in their second summer, and about one year old, more or less. The next 

 measured 94mm. (3^ inches, and was the smallest of a group of 154 

 herrings, apparently the largest of which measured 139mm. (5^ inches). 

 The modal size was 112mm. (4 T 7 ^ inches), the mean 116 5mm., and the 

 arithmetic average 114mm. (4^ inches). There were other four herrings, 

 from 142mm. to 149mm., and a single one at 187mm. The four referred 

 to might belong to the group ; but the indications of other series are 

 against this view ; the series might, on the other hand, so far as the 

 millimetre table indicates, have stopped at 130mm. or 133mm. In 

 either case, the modal size is unaffected, and the average but slightly. 



On the 10th May, twelve herrings were taken, nine of which were 

 from. 117mm. to 135mm. in length, and three from 140mm. to 153mm. 



On the 13th, the collection contained 114 herrings, forming a compact 

 series from 97mm. to 126mm., there being another at 133mm., which is 

 taken as the end of the group. The modal size was 114mm. (41 inches), 

 the mean 115mm., and the arithmetic average 112'3mm. 



If the herrings in this group in the three collections are combined, 

 the number is 277, the apparent range of sizes from 94mm. to 139mm. 

 (3yJ to 5^ inches), the modal size 113mm., the mean 116 5mm., and 

 the average 113'7mm. (4 J inches). 



