THE SEA FISHERIES 277 



net is fishing the catch of the port net is sorted and the 

 net is prepared ready to shoot the moment the other net 

 comes on board. While in most other trawls the " doors " 

 are attached directly to the wings of the net, in a later type 

 there is inserted between each door and the net itself a 

 pair of warps the lower of which sweeps along the ground 

 tending to drive fish inwards. In this way a wider area 

 of the sea bottom is swept, and by using glass floats on 

 the headline of the net its vertical opening is increased. 



The great trawling grounds extend from the White Sea in 

 the north, along the coasts of Norway, around Iceland 

 and the Faroe Islands, the north of Scotland, the whole 

 of the North Sea, and the Baltic, in all the waters that 

 bathe the western shores of the British Isles, in the English 

 Channel, the Bay of Biscay, southward along the coast of 

 Portugal to the coast of Morocco (Fig. 56). Over all this 

 area the catches vary much in composition, owing to the 

 geographical distribution of the fish. The most important 

 food fish caught in the trawl are the haddock, the cod, the 

 plaice, the whiting, the hake, the coalfish and the dog-fish. 

 Other kinds taken in smaller quantities are all flat-fish such 

 as the sole, the turbot, and the brill ; the skates, gurnards 

 and many others. The catches of trawlers are divided into 

 white-fish or round-fish such as the cod, and flat-fish. 



Trawling is chiefly carried out in water down to 100 

 fathoms in depth, but some of the big trawlers when out 

 for hake on the continental slope of the Atlantic have fished 

 in water as deep as 500 fathoms, although 200 to 300 is the 

 more usual depth. WTien fishing over rough ground, round 

 rollers or "bobbins" may be attached to the foot-rope to 

 prevent it catching in the rocks. 



Although, as described below, herring are usually caught 

 near the surface there are certain times when they frequent 

 the bottom and an industry has recently sprung up for 



