420 



THE HERRTNO FAMILY. 



or thereabouts, when the adult habitat is adopted. Here, 

 again, in about three weeks, the young sand-eel grows from 

 17-18 mm. to about 30 mm. Sand-eels of larger sizes are 

 caught at the surface, as almost everywhere, the universal 

 distribution of this species being well known.' 



An inspection of the diagram given here will show that 

 this description will apply in almost every detail to the spring- 

 herring. The sand-eel has a slightly greater average length 

 (30 mm.), on leaving the surface-water, than is the case with 

 the herring, but at this late stage the adult characters are 

 being assumed, and the herring, although shorter, is more 

 robust. The similitude between these two species is completed 

 by the demersal spawning-habit and the occurrence of two 

 spawning-periods during the year, the earlier of which is the 

 more important. These facts serve to emphasise the im- 

 portance of investigations amongst the humbler species of fish 

 which are not themselves used, to any important extent, for 

 human consumption, a study of their life-history affording 

 valuable clues to further knowledge of the more important 

 food-fishes. 



The estimation of the growth of the young herrings is 

 complicated by the double spawning-period, with a space of 

 less than two months intervening. It is probable, however 

 (see diagram), that a maximum length of about 70 mm. (nearly 

 8 inches) is reached by the expiration of 12 months, and this is 

 increased to 12.5 mm. (5 inches) b};- the end of the second year. 

 Spawning probably takes place at the latter end of the third 

 year, when a length of 8 to 9 inches may be reached. 



The mean curve in the diagram for the spring-herring 

 would give a growth-rate as follows : — 



