THE SALT-WATER FISHERIES OF BOHUSLAN. 197 



must they extend their migrations. It is not known from direct obser- 

 vations how far the largest schools of herrings extend their migrations, 

 but certainly much farther than 21acCuUoch, Ifilsson, Boeek, and their 

 followers assert. 



44. The annual migrations of the herrings may be influenced by phys- 

 ical causes both as regards their time and their direction. It is well 

 known that favorable, mild weather accelerates, whilst bad weather 

 retards the approach of the herrings to the coast,^^ and that wind and 

 current may bring a much greater number of herrings to one part of the 

 coast than to another near it. The general rule, however, is that the 

 herrings, when coming in to spawn, visit the j)lace where they were 

 born. When the herrings come in to seek food, they will generally go 

 to those waters where they have been accustomed to find food in the 

 greatest abundance ; those physical causes, therefore, which have an 

 influence on the occurrence of food will also influence the direction of 

 the herrings' migrations, as I have had occasion to remark before. 



45. The annual migrations of the herrings are chiefly caused by the 

 desire to propagate the species and to seek food. For spawning, the 

 herrings need a suitable bottom for depositing their eggs, a bottom 

 which also must contain a sufficient quantity of food for the young 

 herrings and aftbrd shelter for them. All these requirements are only 

 met near a coast. Even if herrings, as has sometimes been said, not 

 without a show of reason, spawn on the Dogger-Bank or other still more 

 distant banks in the North Sea, this does not disprove our assertion, for 

 it is doubtless only the greater ease with which the young fish can reach 

 the coast from these banks which has made it possible for the herrings 

 to spawn there.®'^ 



The grown herrings must again go to the ocean to seek their food, 

 which they chiefly find in the currents and those waters which come 

 from the Polar Sea. In some places, however, they find the required 

 food during some part of the year near the coast ; and thus there may 

 be fishing towards the end of simimer and the beginning of autumn, as 

 on the western coast of Norway, or during autumn and winter, as on 

 the coast of Bohuslan. The influence which the desire for food exercises 

 on the annual migrations of the herrings has sometimes been overrated, 

 so that it has occasionally been considered as the chief cause, even in 

 cases when the desire to propagate was undoubtedly the principal cause. 



As the spawning herrings, on account of theii' being packed more 

 closely together and on account of the steady course which they pursue, 

 are more exjDosed to the persecutions of their enemies, and as this danger 

 of course increases the nearer they get to the coast, they generally go 



•>' See 13. This is applicable cliietiy to those Lerriugs which spawn iu spring (that is, 

 after the close of winter when the ice is breaking up). On coasts hke those of Nor- 

 way and Scotland, laved by warm currents of the sea, this is less noticeable. 



''^It is therefore not improbable that the young herrings which in such large number 

 are found near the western coast of Norway are at least in part the offspring of her- 

 rings which have spawned on the North Sea banks. 



