70 



PELAGIC FAUNA 



A large bristle-worm (Notopygos gigas), taken in angling off the Seychelles. Top, from above; 

 below, the ventral side. Two-thirds natural size. 



For gathering small pelagic fauna which could not be taken by dip 

 net we used a net of silk, 50 centimetres in diameter. It was suspended 

 over the side so that the creatures would drift into it with the current 

 (Fig. p. 72). Sometimes also we used a large pankton net of stramin; 

 and our large herring trawl on its way up from a bathypelagic haul 

 would always catch some of the animals of the upper water levels. Crusta- 

 ceans nearly always formed the bulk of the haul, and in the vicinity of 

 land there was always a number of free-swimming larvse of various 

 bottom dwellers like snails, mussels, worms, echinoderms, and so on. 



A selection of common epipelagic animals is shown in the figure on 

 page 71, which also illustrates the great variety of ways in which animals 

 can adapt themselves to pelagic life. Even pelagic animals are nearly 

 always heavier than water and must provide against sinking too deep. 

 To remain buoyant by swimming requires energy, but most fish and ce- 

 phalopods manage without special contrivances. A sphere sinks more 

 rapidly than a broad and flat object or a long and thin one. And so we 

 find that many pelagic animals are broad and flat, or rod-shaped like 

 the arrow- worms (Sagitta). Long extensions at the front, the back, or 

 the sides are common means of floating and these are particularly pro- 



