254 THE COMMERCIAL SEA FISHES OF 



he never perceived the shoal to swim in a contrary 

 direction. 



Migrations. Many theories have been broached to 

 account for the migrations of the herrings, and it is still a 

 subject which requires much elucidation. 



Some suppose that this fish is not, strictly speaking, 

 migratory, that is, that it does t not travel comparatively far 

 from the locality in which it was hatched, reared, and came 

 to maturity, but simply changes from shallow to deep 

 water, in accordance with temperature and the supply of 

 food ; one proof advanced being that certain definite 

 varieties are present in certain waters. Where they conceal 

 themselves is certainly remarkable ; thus along the Devon- 

 shire and south-west coast of England, Mr. Dunn observes 

 that should a gale spring up numbers are taken in nets 

 purposely anchored parallel to the shore, and that they are 

 meshed on the land side, although this locality had been 

 unsuccessfully swept by seines and nets a very short time 

 previously. 



That herrings, in common with other species of the 

 herring family, will occasionally disappear from one local- 

 ity, sometimes re-appearing in another, is well known. 

 From 1690 to 1709, a very extensive herring fishery 

 existed at Cromarty ; about the latter year an immense 

 shoal was driven ashore near the town : they left the 

 vicinity in a single night, and for upwards of half a century 

 no shoals re-appeared : still this may have been simply a 

 coincidence. 



In Sweden it has been supposed that certain cycles occur 

 during which herrings are found on their coasts ; that the 

 fish at the commencement of one of these cycles arrives late 

 in December or January ; by degrees they come earlier, 

 and as soon as their advent is in October, it is considered 



