308 EIGHTH PACIFIC SCIENCE CONGRESS 



the times and conditions under which these occurrences take place, and 

 even of the fluctuations in relative numbers of fish appearing from time 

 to time. But this would still be insufficient: the cannery operators 

 need to have some indication of the level of abundance in order to be 

 able to decide the amount of fishing equipment (craft and gear) which 

 could be brought to bear on the stocks, and thence the amount of pro- 

 cessing equipment which would be required to handle the catch. 



There are probably two broad avenues of approach to this prob- 

 lem. One is by way of evaluation of the area in terms of basic pro- 

 ductivity and measurement of food chains. This would be possible 

 only for stocks endemic to the area and not to transients. The other 

 approach is by way of special sampling which, in the case of pelagic 

 stocks, may include aerial observation. It may be noted that in this field 

 of work there is urgent need to elaborate and improve the methodology 

 of searching and sampling, and that in such improved methods, even 

 greater use must be made of reference to oceanographic factors as de- 

 terminants of the behaviour of the fish. 



In the more general sense of the productivity of an area, the ocea- 

 nographer must take a leading role, and the task of the fishery biologist 

 is to develop the understanding of the nutrition of the economic species 

 in order to be able to use the data on food availability. 



We now turn to the other two problems concerning abundance. 

 The structure of the problem was symbolized by Russel, in his well- 

 known equation, which says that the difference in a stock of fish, be- 

 tween one season and another, can be represented by the balance 

 between. 



Growth + Reproduction and Natural Mortality + Fishing Mor- 

 tality. We may take these four elements as the plan for our enquiry. 



Growth:— The growth of any individual may be taken to be the 

 result of the operation of factors which may be considered in three 

 groups— genetic, food supply, and the environmental factors affecting 

 food procurement and the subsequent metabolism; between these arise 

 interactions. In the past fishery biology has concerned itself chiefly with 

 measuring and describing the ontogenetic manifestations of growth: it 

 has made little analysis of growth itself as physiological process. The 

 initial approach made by fishery biology to growth has furnished a 

 useful description of growth phenomena at what might be called their 

 grosser level, and some attempt has been made to measure the relations 

 between these phenomena on the one hand, and food availability and 

 environmental conditions on the other. Whether much further progress 

 can be made along this line before more detailed enquiry is made into 

 the physiology of growth might be questioned, but both types of enquiry 



