26 THE EXPLORATION OF THE SEA [PART I 



used their otter trawls for the capture of herring, by so manipu- 

 lating them that the nets sweep through the water before 

 descending to the bottom, or fish a considerable part of the sea 

 while being hauled. But as a rule quite different kinds of fishing 

 apparatus have to be employed for the capture of pelagic animals. 

 The drift net and the seine employed in the Firth of Clyde for 

 the capture of herring are commercial fishing instruments and are 

 little used for scientific investigations. The drift net is simply a 

 vertical wall of netting of great dimensions which is allowed to 

 drift in the sea near the surface. Fishes striking against it are 

 enmeshed, since the diameter of the meshes is less than the 

 average diameter of the body of the fish. The seine net used in 

 Loch Fyne is a large net which is " shot " round the shoal of 

 herring, and is then hauled so that it forms a huge pocket in which 

 the fish are contained. 



The tow-nets. The tow-net of the naturalist, that is the 

 traditional instrument, is a conical bag of some fine fabric, such as 

 muslin or silk, or even fairly coarse canvas. This bag, which is 

 about three or four feet in length, is attached to a ring of iron by 

 means of a wide hem or strip of some stronger material. The end 



Fig. 12. The ordinary surface tow-net. 



of the net may simply be the termination of the cone of fabric, or 

 there may be a bottle of metal into which the catch of the net is 

 washed when it has been hauled. The net is towed by three 

 bridles which are attached to equidistant parts of the ring, and 

 which are then attached to the tow rope. It is towed at a low 

 rate of speed. When the tow is completed the net is hauled, 

 turned outside in and the catch, which consists of small, usually 

 microscopic organisms, adhering to the walls of the net, is rinsed 



