OCEANOGRAPHY AND FISHERIES 307 



At this point we are concerned only Avith the types of fauna found 

 in various situations, with the task of characterizing an area in respect 

 of the composition of its fauna and, for situations whose fauna is known, 

 with evolving means of predicting variations in the distribution of ele- 

 ments of that fauna and of ontogenetic stages of those elements. 



The role of oceanography in this phase of the programme emerges 

 very clearly; it must first furnish the description of the physical, chem- 

 ical and biotic properties of the water masses and in this way it cor- 

 responds to soil science coupled with climatology. Then, when the 

 distribution patterns are revealed, the role of oceanography corresponds 

 to that of meteorology in furnishing predictions as to the conditions 

 which are likely to be found, and the task of the fishery biologist then 

 is to predict the behavioral response of the fish stocks to such conditions. 



4. Oceanography and the Abundance of Fish 



In this part of the programme we may consider three types of prob- 

 lems having common basis. We are concerned with the natural abun- 

 dance of fish in an area, a problem which has practical meaning only for 

 unexploited areas, although a method of estimating potential natural 

 abundance of an exploited stock might solve many of the problems 

 concerning abundance under conditions of exploitation. Next we are 

 concerned with the fluctuations in abundance which have manifested 

 themselves in all exploited stocks, whatever the degree of exploitation. 

 Finally, we are concerned with the special problem of the effect of fish- 

 ing operations on the abundance of the stock. 



The measurements of natural abundance of stocks in virgin areas 

 is a task of peculiar- difficulty which demonstrates, perhaps more than 

 anything else, the special character of the work of fisheries science and 

 the abstruseness of its problems. A simple example will serve to indi- 

 cate the nature of the problem and the difficulties. Somali fishermen 

 have for many years been catching tunas off the Somali coast, and for 

 some years a few small canneries have been processing this catch for 

 export market. The canneries would like to expand their operations 

 and therefore require to increase their catch of tuna; the question is: 

 do substantial stocks of tuna, accessible to fishing craft operating from 

 Somalia, inhabit the waters on the Arabian Sea east of Somalia, or, are 

 the occurrences from which the fishermen have made their catch merely 

 sporadic invasions from a principal area lying somewhat remotely from 

 Somalia? This, it will be noted, is not a simple distribution question, 

 for the tuna are well known to a^Dpear in these waters. It might be a 

 question of ontogenetic distribution pattern and the determination of 

 this possibility could lead to development of a system of prediction of 



