556 NATURAL HISTORY OF AQUATIC ANIMALS. 



"The going out of the Herrings is generally a much quicker process than their coming in, and 

 as it is more difficult to catch Herrings whilst they are leaving the coast we know very little about 

 it. After the Herrings have left the coast they do not stay outside any length of time, but imme- 

 diately go out to sea to seek food and enjoy the greater protection which the deeper water affords. 

 When the Herrings have been to the coast for the purpose of spawning they generally leave the 

 coast in a northerly direction. 



"With regard to the extent of the annual migrations of the Herrings I have already mentioned 

 the different opinions, and I will only add here that the larger a school of Herrings is the greater 

 will be the extent of territory where they must seek their food, and the' farther from the coast must 

 they extend their migrations. It is not known from direct observations how far the largest schools 

 of Herrings extend their migrations, but certainly much farther than Macculloch, Nilsson, Boeck, 

 and their followers assert. 



" The annual migrations of the Herrings may be influenced by physical 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 place 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 Herring's 

 migrations, as I have had occasion to remark before. 



"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 

 afford 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 summer 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, evt n in cases when the desire to propagate was 

 undoubtedly the principal cause. 



"As the spawning Herrings, on account of their being packed more closely together and on 

 account of the steady course which they pursue, are more exposed to the persecutions of their 

 enemies, and as this danger of course increases the nearer they get to the coast, they generally go 

 into deep water immediately after having spawned, in order to find the necessary shelter, and 

 leave the coast much quicker than they came. The larger Herrings seem likt-wi e to thrive better 

 in the open sea than near the coast, and consequently do not stay there longer than is absolutely 

 necessary. Nencrantz, however, goes too far when he supposes that the Herrings leave the coast 

 only to escape unpleasant physical conditions; for instance, cold or violently agitated water. It 

 has already been mentioned that want of space or the persecutions of enemies have in former 



