— Hr 
The fishing was carried on off the west coast of Scotland, at the Shetlands, in the 
waters north of and on the Dogger Bank, and southward towards the coast of Hol- 
land. Only off the west coast of Scotland and the Shetlands were any fat herring (matjes) 
caught, the catches otherwise consisting entirely of grown fish with large roes and milt, 
or spawning and spent fish. 
A study of the samples collected from the fishermen’s drift net hauls gives an ex- 
actly similar result. These samples show the length of each individual fish in cm., the 
sex, and degree of maturity of the genital organs*). In addition to this, the age of each 
individual, and size at all different periods of growth, (L,, ts, t;, etc.)**) have been deter- 
mined on the basis of the scales collected. 
Only in the waters west of Scotland and round the Shetland Isles are immature 
fish found early in the season, and in the autumn, some few samples from the southern 
half of the North Sea may be found to contain a greater or lesser admixture of imma- 
ture fish. 
As regards age, by far the most part of the fish are over three years old; in the great 
open sea fishery carried on in the northern half of the North Sea, the rule seems also 
to be that the three year old fish are slightly represented in the samples. (See Table 
p. 63). 
Distribution of the youngest year classes. 
The drift nets of the North Sea fleet are thus evidently adapted to the capture of 
grown herring, and other implements must be used if it is desired to obtain information 
as to the distribution of the younger, immature age classes. 
Such investigations have not previously been made in the open waters of the North 
Sea. Information is to hand from the different countries bordering on the North Sea 
as to the occurrence of small herring along the coasts, and these fish have also in many 
places been measured and described, as for instance in Scotland, (Firth of Forth, Moray 
Firth), England (Plymouth) Holland, Germany, and Denmark. No closer investiga- 
tion of their subsequent growth and habitat has, however, been made. It is also a matter 
of great difficulty to study these conditions on the open coasts of the North Sea, the 
services of a steamer and the employment of many kinds of implements being required. 
The question appeared to me however, to be of the utmost importance for the study 
of the natural history of the herring in the North Sea. I therefore made, in 1912, several 
cruises in the North Sea with the “Michael Sars” exclusively for the purpose of studying 
the distribution of the younger stages of herring, my Assistants, E. Koroep and E. Lea, 
accompanying me. The cruises were carried out in June —July, and October—November, 
in order to compare the conditions prevailing in summer with those of autumn. The 
implements used were a fine-meshed trawl of the same construction as those employed 
by the Swedish fishermen, and a fleet of drift net composed of a series of nets of greatly 
varying width of mesh. 
The drift nets used were as follows: 
a) Sprat net. Width of mesh (from knot to knot)........ il em. 
b) — | N SE TURIN irs NS OL Mec ee 1.2 » 
*) See note p. 52—53. 
**) Examples will be found in Publ. de Circ. No. 53, pp. 139—159. 
