74 BRAIN AND BODY OF FISH 



It would appear that the vibrations of the screw and the dis- 

 turbance produced by the oars is not sufficient to frighten the fish, 

 but the noise produced by " beating " is so alarming that the fish 

 dive to the bottom and are then enmeshed in the nets, which extend 

 some seven fathoms down below the tliree fathom level, at which 

 the net commences ; the reaction of the fish to loud noises is to make 

 them dive ; if they did not dive they would swim safely above the 

 net. Nature does not visualise that the danger is below, and in 

 swimming from the noise they become entrapped in a danger in 

 the depths. Another Clupeoid, the pilchard, is readily alarmed by 

 noises ; and the firing of a heavy gun at a distance of twenty miles 

 has, according to Couch, been known to cause the fish to sink. 



Another example of noise being used in fishing is in the method 

 of seining for grey mullet that has been practised in Chichester 

 harbour from time immemorial ; this fish is very difficult to catch 

 with a net ; when surrounded by the net, they endeavour to leap 

 the cork line, to obtain their freedom. The fishermen, to prevent 

 the fish leaping, beat the water frantically with an oar ; others wade 

 waist deep making the welkin ring with shouts and oaths ; here 

 again the fish fail to reach safety and dive to destruction. 



This method of fishing for mullet is not confined to the fishermen 

 of our south coasts. We have been told by one of the naturalists 

 of the Ministry of Agriculture and Fishery, R. S. Winpenny, of 

 the fishing for mullet in Egypt in which similar methods are 

 employed 



As a result of the above observations an examination of the brain 

 of the grey mullet was undertaken and the size and structure of the 

 acoustic tubercles and central acoustic area examined. Here is a 

 fish which has well defined reactions to noises, and it was to be 

 expected that this area of the brain would show some specialisation 

 in connection with the function of audition. It was, therefore, not 

 surprising to find that this fish has a very well-developed central 

 acoustic lobe. 



