but others conceivably might support fisheries rivaling those of the 

 Japanese islands or those of the American west coast. 



There are in addition vast sea areas as yet totally unexplored 

 for tuna possibilities., Our imperfect but growing stock of knowl- 

 edge concerning the oceans and the tunas suggest that concentrations 

 of these fish occur in regions marked by fairly definite types of 

 oceaji circulationo The essential features seem to be the propaga- 

 tion or the accumulation of planktonic organisms in unusual concen- 

 trations affording food directly to the tunas or to the small fishes, 

 squids and other marine animals which in turn are fodder for the 

 tunas o The apparently effective types of circulation are: mass ujd- 

 wellings off continental edges generated by certain prevailing wind 

 systems i, interfaces between major ocean water masses of contrasting 

 hydrographic properties, divergence-convergence combinations related 

 to wind systems J and other oceanic situations causing convergence if 

 on sufficient scale. It is probable that the concentrations of tuna 

 are roughly proportional to the intensity and stability of these cir- 

 culation systems but also modified by particular biological require- 

 ments of the fish themselves. Since many of the regions with the 

 above listed types of circulation have not been assayed as to in- 

 tensity and there is little precise knowledge on the biological re- 

 quirements of tuna^, their effectiveness in supporting large tuna 

 resources cannot be predicted. 



Nonetheless, study of current chsirts of the oceans is impres- 

 sive for the number of totally unexplored situations which seem to 

 fill at least some of the requirements for supporting large tuna 

 populations. For instance the equatorial circulation of the Atlantic 

 and Indian Oceans may be expected to have a divergence-convergence 

 system similar to that of the Pacific which has already proved ef- 

 fective in supporting a considerable tuna population. In the Atlan- 

 tic and Indian Oceans, however, the systems are geographically short- 

 er from east to west and the accumulated effect of winds with long 

 fetch may therefore be less pronounced. Also with reversing monsoons 

 in the Indian Ocean there may be seasonal interruptions which may 

 destroy the integrity of the system periodically. The huge gyral 

 in the northeastern Pacific may constitute an even more effective 

 convergence than the more linear one stretching across the western 

 north Pacific Ocean. The north flowing current at certain seasons 

 along the west coast of Australia bears similarities to those off 

 the west coasts of SoiTth America and Africa which 'haVe aTiready 

 proved to harbor tuna populations of note. Even the interface of 



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