of the Fishery Board for Scotland. 



77 



This table shows that although the mature and immature fish are found 

 covering a common ground of variation, the immatures in general have a 

 slightly less depth at the shoulder, relatively to the length of the body 

 (only) than the mature. A further and detailed examination of each of 

 the mature fish included in the figures of this table shows that the relative 

 depth of the body is not altogether affected by the length of the fish, all 

 lengths being represented in each of the above divisions. 



Regarding what is generally called the size of the herring, that is, its 

 bulk, opinions differ very much ; but there seems to be a general belief 

 that the fish vary in this respect according to the locality which they 

 frequent, and that such variation is pretty constant. The tables given 

 above show that so far as length and size at the shoulder go, there is not 

 such a marked difference between our local forms as is often supposed ; 

 but in respect to bulk there is some ground for the belief. This is not so 

 much due, I think, to an actual difference in the size of the fish, as partly 

 to the difference in the size to which the roe or milt attains, and 

 especially to the amount of fat developed before the spawning season. 

 For instance, the Campbeltown and neighbouring herrings seem to have 

 larger roes and milts, when fully ripe, than those of the South-East Coast of 

 Scotland, and there is nearly always to be found in them, especially in 

 those frequenting Loch Fyne, a much larger quantity of fat along the 

 intestine, air bladder, &c. This has a considerable influence in the 

 estimation of size by bulk, but it does not necessarily mean a longer or 

 even deeper fish, as may be seen when they are compared without these 

 adjuncts, as, for instance, in the spent condition. Of course, in estimating 

 the size of these herrings, care must be taken only to compare those in 

 actually the same sexual condition ; for estimation by cran measurement 

 will be influenced a good deal by this, even where the herrings are 

 supposed to be assorted into fulls, spents, maties, &c. Lastly, the size 

 of mesh generally in use in the various localities will affect these results. 



From this examination of the general size of the herring at all seasons 

 and in all localities around Scotland, it appears to me inadvisable to lay 

 too much stress on the not very extensive differences of length which are 

 found among them, as indicating that these herring belong to more than 

 one race or variety. The difference apparent in such a comparatively 

 limited examination as we can undertake may be partly caused by circum- 

 stances attending the capture of the fish. But there can be little doubt 

 that the effect of temperature, not only on the developing ova, but more 

 especially on the young and growing fish, as well as the amount of food at 

 their command, must have considerable effect on the ultimate size of the 

 fish, and these effects — perhaps considerable in one season so far as the 

 numbers of fish go, only to be corrected in another more favourable — will 

 to some extent influence the proportion of small and large fish in the 

 shoals frequenting the spawning grounds. We can scarcely, then, I think, 

 distinguish as regards size the herring of any particular locality, or, per- 

 haps, even seasons, by a preference over the others, without further 

 confirmatory evidence, such as might be brought out by an examination 

 of differences in other characteristics and the common presence of one or 

 more of such specially in the fish of any one place or season. 



Size of Head. 



In dealing with this question, as well as with the position, length, (fee, 

 of fins and other external characters, the results, so far as yet worked out, 

 must be stated in even more general terms than was necessary in referring 

 to the size of the whole fish. We can scarcely class the herrings under 



