24 



THE SCIENTIFIC AND ECONOMIC ASPECTS 



of the pilchard to shoal more densely during the night and 

 thus to minimise the danger of attack from predatory fishes. 



Fishermen generally state that dogfish will not enter into 

 the midst of a close shoal, owing to the pollution of the water 

 by the excrement of the densely packed mass, but prefer to 

 harass the flank, carrying on as it were a kind of guerilla 

 warfare, and it is possible therefore that in venturing almost 

 upon the shore at day-time, as the pilchard undoubtedly does 

 during the height of inshore migration, the fish feel a certain 

 amount of security from their natural enemies. 



That a return to deeper water at dusk certainly does take 

 place is evidenced by the fact that when the drift nets are 

 shot parallel to the shore the catch is invariably taken on the 

 one side of the fleet. 



The present authors, on certain occasions when the fishery 

 was being carried out close to the coast line, have observed 

 the actual movement of a shoal coming off the shore. The 

 experience, however, is by no means a common one, and fisher- 

 men agree in stating that a good catch can generally be antici- 

 pated when the occurrence is sufficiently evident to be seen 

 and heard. 



So far as our personal observation is concerned, it may be 

 stated that at the time of movement we have seen the surface 

 of the sea presenting an appearance as if fine rain was falling 

 upon it. A peculiar rustling sound, similar to the wind dis- 

 turbance of fallen leaves, accompanied this visual impression, 

 but this is seldom sufficiently pronounced to be detected by the 

 ordinary observer, though many experienced fishermen assert 

 that they can " hear the fish coming " even when the light is in- 

 sufficient for them to see the appearance of the surface of the 

 water. In the course of our personal experience we have never 

 found such a statement, when made by a fisherman, to be in- 

 correct if we may take the extent of a catch as evidence. It may 

 be stated also at this point that many fishermen are able to 

 detect the presence of pilchard by their sense of smell, and 

 this is quite credible when we consider the peculiar rankness 

 of the odour emitted from the freshly caught fish. 



But whatever speculative views we may enter-tain with 

 regard to the actuating cause of this supposed movement off 



