250 POPULATION'S OF THE SEA 



The Other and main period of intense aggression which comes in 

 late summer and early autumn, and which gives rise to dominance 

 and dispersal of either sex by both sexes would lead to the dispersal 

 of individuals at small distances from each other thus ensuring for 

 each fish a better chance to get food. 



Of importance to all these ideas is the finding that grunting 

 (whether in courting or aggressive display) only affects fish which 

 are not more than 2 ft away from each other, and no evidence 

 was found that it triggers off mass stimulation ; and secondly, that 

 the "flaunting" display, an essential component of natural court- 

 ship in the cod, seems to be a visual releasing mechanism, although 

 it takes place only in crepuscular light. There can be no doubt 

 that at these times of great aggression (September to November) 

 and again at prespawning aggression as well as during actual 

 spawning the ocean where the cod shoals are congregated must be 

 full of the sound of cod grunts. 



This suggests that the use of hydrophones to find cod would be 

 of value, but only seasonally. But it also emphasizes that the 

 accurate recording, identifying, and classifying of underwater 

 noises of all kinds is an important section of the contributions 

 which beha\ior study has to make to oceanographical problems. 



W^ithin the whole field of behavior research possibly no general 

 class of experiments is so well known as those into the ability of 

 animals to show insight into configurational problems, of which 

 Koehler's investigation of the detour performances of chimpanzees 

 is a classical example. Thorpe (1958) reviewed some of this work 

 briefly so far as it relates to fishes. \A hat it is desired to stress 

 here is that this kind of study has relevance to the design of 

 traps of all kinds used in the capture of fishes, crustaceans, etc., 

 and that it could well lead to substantial modifications in design 

 in traditional trapping techniques. Arising out of a general propo- 

 sition to study configurational learning in the cod, Miss Brawn 

 was led on to a general study of the ability of cod to learn detours. 

 She has discussed and illustrated this additional avenue of 

 exploration (1959). 



The late Sir John Graham-Kerr, one-time Chairman of the 

 Fisheries' Advisory Committee of H.M. Development Commission, 



