CONSIDERATION OF INDIVIDUAL FISH 95 



herring is within the Arctic Circle ; there they continue for many 

 months in order to recruit themselves after the fatigue of spawning." 

 After describing the separation of the shoals into the eastern and 

 western " brigades," Pennant goes on to say, " Were we inclined 

 to consider this partial migration of the herring in a moral light, 

 we might reflect with veneration and awe on the mighty Power 

 which originally impressed on this most useful body of His creatures, 

 the instinct that directs and points out the course, that blesses and 

 enriches these islands, which causes them at certain and invariable 

 times to quit the vast polar deeps and offer themselves to our 

 expecting fleets. That benevolent Being has never, from the earliest 

 records, been once known to withdraw this blessing from the whole, 

 though He often thinks proper to deny it to particulars ; yet this 

 partial failure (for which we see no natural reason) should fill us 

 with the most exalted and grateful sense of His providence, for 

 impressing so invariable and general instinct on these fish towards 

 a southward migration, when the whole is to be benefited, and to 

 withdraw it only when a minute part is to suffer." 



Although much time has been devoted to the investigation of the 

 habits and life-history of the herring since Pennant wrote the above, 

 there is still much that is obscure in the movements of the shoals 

 of this the most abundant and valuable of our food fish. 



The egg and young, and some of the spawning grounds are well 

 known ; and, as will have been gathered from the preceding pages, 

 the herring is remarkable in that it is practically the only com- 

 mercial species of bony marine fish which has demersal eggs, that is 

 eggs which are laid on the bottom and there undergo their develop- 

 ment (Fig. 96). 



Even the other members of the herring family, such as the sprat 

 and pilchard have pelagic eggs. The egg of the herring varies from 

 0-92 to I mm. in diameter, and the average number of eggs carried 

 by an adult female is about 30,000. This is quite a moderate 

 number for a marine fish and is far below that produced by most 

 pelagic-egg producing species. In most districts where herring 

 abound there is evidence of two main spawning seasons, one in the 

 spring and the other in autumn, and this fact has given rise to the 

 theory that there are two main races of herring, spring and autumn- 

 spawning herring. This question of the races of the herring will be 

 briefly touched upon later. 



The development of the herring does not present any exceptional 

 features, and since it is described in some detail "in the works of 

 Cunningham! and Mcintosh, « further reference to it is omitted here. 



' Marketable Marine Fishes. London, 1896. 

 « British Marine Food-fishes. London, 1897. 



