mr 
on exelusively along the coast, in bays or fiords. The only great fishery at this time of 
year is the Norwegian spring herring fishery, which is carried on especially in March— 
April, and the Bohuslän fishery in January. 
The months from May to August form the season for the great Scottish and northern 
English fishery; May for the west and north-west coast of Scotland, June—July for 
the Shetland Isles and the east coast of Scotland, and August also for the coast of nor- 
thern England. 
For the last four months of the year, the herring fishery is for the most part restrieted 
to the southern waters of the North Sea: in September from the Tyne to the Dogger 
Bank, in October from the Dogger to Lowestoft and Yarmouth, and in November and 
December between the coasts of England and Holland. 
Following the successive appearance of the fish from the Shetlands southward, the 
fishermen shift from one fishing ground to another. It would be very natural, from this 
occurrence of the herring, to deduce a great migration from the ocean north of the 
North Sea southward to the shallower waters of the banks in its southern part; a 
theory, which, as we have seen, is of very ancient origin. 
Difference of opinion as to the migrations and race of the herring. 
In course of time, however, as more extensive experience was obtained, many doubts 
and differences of opinion arose concerning this migration theory. The fishermen noticed 
that the herring were not everywhere of the same “sort”; that different sizes and “quali- 
ties” appeared at different times and in different parts of the North Sea. This led many 
to conclude that there were in the North Sea a great number of different local races of 
herring, each with a very restricted area of movement, and that the peculiar seasonal 
occurrence was only due to the fact that the fish, during the period of developement 
of the genital organs, congregate in denser shoals, rendering fishery profitable. Between 
these two extreme opinions, that of a great general migration and that of a number of 
local races, various other theories have arisen, and there exists a great number of works 
dealing with the different hypotheses. 
Scientific works on the subject have also, ever since the time of Linn£, distinguished 
between different races or varieties of herring; there has, however, as LILLJEBORG ob- 
serves, always been a difficulty in classifying them according to definite and constant 
characteristics. Linné, in his “Fauna Suecica”, distinguishes between two varieties, « 
and #; the first he designates harengus, or herring in the true meaning of the term, the 
second membras or “Stremning’’; the herring of the Baltic. It is very natural that Swe- 
dish investigators should be well acquainted with the difference between the herring 
of different waters, since the coast line from the Gulf of Bothnia in the north round to 
Bohuslän presents opportunities of studying herring living under extremely different 
conditions. Sweden has therefore also furnished most valuable contributions to the 
natural history of this fish. Thus Ninsson, in his “Scandinavisk Fauna” of 1855, 
divides the races of herring as follows: 
1) The ocean form, including a) Norwegian spring herring and b) Goteborg or Bo- 
hus herring. 
2) North Sea coastal water forms, a) Kulla herring, and b) Norwegian summer or 
autumn fish. 
3) Baltic forms, including the “Stromning”’. 
