422 THE HERRING FAMILY. 



There is considerable difference of opinion with regard to 

 the varieties of herring which frequent the coast of Scotland. 

 Dr Heincke came to the conclusion that the Baltic herrings 

 were of two varieties, and that each of these varieties could be 

 subdivided into a summer- and an autumn-variety according to 

 their spawning-period. The spring-herring of the Baltic appear 

 to spawn in brackish, shallow water, and in the Schlei they 

 spawn in water that is practically fresh. They thus form a 

 transition-type, through the shads, to the regular freshwater 

 demersal-spawning fishes. 



Duncan Matthews, after an exhaustive examination of a 

 great number of Scotch herrings, was led to believe that the 

 summer- and winter-herrings could be distinguished by small 

 structural features, such as the ' more posterior position of the 

 dorsal, pelvic and anal fins, the doubtfully smaller head and the 

 slightly lesser size ' of the former, but he considered that the 

 differences were not sufiSciently defined to warrant the term 

 ' variety ' being applied. If it were a difference of size alone 

 the larger mesh of the nets used in the winter would probably 

 account for the fact. All questions with regard to the later 

 rate of growth and the prevailing abundance of herrings of 

 different sizes are complicated by the fact that herring-nets 

 catch i^ractically only one size of herring. (See Rate of 

 Growth.) Valenciennes gives 13^ inches as the maximum 

 length attained by the North Sea herring. 



So far as one can pronounce with any certainty upon a very 

 difficult point, we may say that the herring attains sexual 

 maturity at a length of 8 — 9 inches, and this is probably during 

 the third year. 



From the diagram it will be seen that the sizes 3 inches 

 and 5 inches may be taken to represent a rough average of the 

 size of a herring when one year and two years of age re- 

 spectively. 



The Pilchard. (Glupea pilchardus, Walb.) 



This member of the well-defined clupeoid group of food- 

 fishes is intermediate in size between the herring and the sprat, 



