290 BRITISH FISHERIES 



a greater size, and for all practical use they are, 

 they may as well be carted away for manure. 

 It is true that they produce spat, which may 

 lead to the formation of new mussel-beds in 

 better localities, but there is no scarcity of mussel 

 spat in most localities. The mussel, however, is 

 a sedentary animal. It is fixed on the place 

 where it grows, and has a most limited range 

 of movement. It is quite different with the small 

 flat fishes on the shrimping grounds or on the 

 "Eastern Grounds" of the North Sea. The 

 investigations made on the life-history of the most 

 abundant of these fishes — the plaice — show that 

 it lives during the first two years of its life on 

 shallow, sandy flats, grows there till it is about 

 6 to 9 inches in length, and then begins to migrate 

 outwards into deeper water. These shallow inshore 

 areas are therefore " fish-nurseries " which "feed" 

 the fishing grounds offshore where the larger fish 

 are found. On the other hand, the mature plaice 

 on the latter areas spawn, and the eggs drift in- 

 shore, where the little fish, when it is hatched, 

 passes through its post-larval and immature stages. 

 In the " Eastern Grounds " of the North Sea we 

 have such a fish-nursery on a large scale — a 

 nursery which owes its position to physical causes. 

 The general drift of the surface water in the 

 North Sea is such as to cause small objects floating 

 on the surface to move down the north-east coast 

 of Great Britain as far as Norfolk, while at the 



