GENERAL DISCUSSION 



INTRODUCTION 



The programme of the Symposium included three 'general discussions' on 



the subjects: 



(i) Is it relevant to construct a comparative population dynamics? 



(2) The response of populations to exploitation and the operation of density 

 related factors. 



(3) The management of exploited populations (intended as a summary of 

 the Symposium). 



Discussion on these three topics was opened by brief, prepared statements 

 by D. H. Chitty, M. E. Solomon and G. C. Varley and M. Graham respec- 

 tively. In practice, the discussions tended to depart from the intended topics, 

 to overlap with each other, and often to develop ideas first put forward in 

 the discussions following the papers. The records have therefore been 

 combined and rearranged and are presented here under the seven headings 

 listed below. Some of the remarks made were repetitive or irrelevant to a 

 printed version and so have been omitted; otherwise the spontaneous 

 spoken remarks have been subject to only minor editing. 



CONTENTS 



Page 



1. Characteristics of stable populations 361 



2. Oscillations and trends ........ 3^3 



3. The influence of environmental change ..... 368 



4. Behaviour and comparative population dynamics . . -370 



5. The response of populations to exploitation and the operation of 



density-related factors . . . • • • -373 



6. Terminology ......... 37^ 



7. Mathematical models . . . . • • • .381 



I. CHARACTERISTICS OF STABLE POPULATIONS 

 S. J. Holt: I think that today, when we were discussing the 'damping 

 effect' of age-groups, we were confusing 'life-span' and 'mature life-span'. 

 In fact the critical relation is that between the mature life span and the 

 frequency of reproduction. For example, an anchovy in tropical waters with 

 a two-year life-span, shows no more fluctuations than does a cold-water 



