FISHERY RESEARCH 329 



it has reached a length of about one and a half inches and 

 can swim too rapidly to be captured by the tow-net. At 

 this stage the fish congregate in shoals and their movements 

 become very hard to follow. We have no really efficient 

 instrument for catching them in the open sea, but they may 

 be caught by fishing off sandy shores and in estuaries by 

 means of very fine-meshed seine nets. In fact recent 

 research points rather to the fact that it may not be 

 necessary to search in the open sea for the herring at this 

 stage in its life-history, for it is beginning to be realized 

 that the numbers present in the estuaries are very great 

 and probably quite sufficient to give rise to the large supplies 

 of adult herring caught by the fishermen in the open sea. 

 At certain seasons of the year, for instance, the whitebait 

 that abound in the Thames estuary consists almost solely 

 of young herring (Plate 119). When the herring reaches a 

 length of three or four inches it probably leaves the estuaries, 

 and little is as yet known of its movements until it grows 

 to a size large enough for capture by the nets. In the case 

 of quick-growing fish probably the end of the second 

 year is the time at which they are large enough to appear for 

 the first time in the net catches ; the fish would then be 

 about six inches in length. But more usually the herring 

 are not large enough to be taken in the drift nets until 

 they are three years old, or at any rate in their third year. 

 It is difficult to follow the movements of the adult fish. 

 They are too delicate to be marked like the plaice. Any 

 one who has handled a fresh herring knows how easily 

 the scales come off and if the fish is returned to the water 

 with many of its scales removed the large surface of bare 

 skin thus exposed soon becomes infested with bacterial 

 and other parasites and in a very short time the fish 

 succumbs. It is therefore practically impossible to mark 

 the herring with any hope of their survival. 



