does not, however, preclude further development 

 of local stocks in the Gulf of Alaska, the Gulf of 

 Mexico, and several other areas. Very recent egg 

 and larvae research suggests, however, that even in 

 the North Atlantic very large populations of sand 

 lance and blue whiting are being exploited at very 

 low proportions of their potential yield. 



The Southern Hemisphere does have under- 

 utilized demersal stocks, particularly in the waters 

 off both coasts of South America and New 

 Zealand, and further development will occur off 

 West Africa. This is tempered, however, by the 

 fact that nearly 70 per cent of the Continental 

 Shelf areas of the world Ue in the Northern 

 Hemisphere, and most of these areas are rather 

 intensively exploited. As a rough estimate, we 

 might assume that demersal fish stocks are now 

 providing about 60 to 80 per cent of their total 

 potential, given present techniques and market 

 preferences. The ultimate potential may be much 

 greater. 



Pelagic fish stocks (tuna, sardines, jacks, 

 anchovies, hakes, etc.), have considerable potential 

 for increased production. As with demersal fish, 

 utilization is now most intensive in the Northern 

 Hemisphere, and the potential for growth is 

 greatest in the Southern Hemisphere and in the 

 Arabian Sea. It is extremely difficult to fix the 

 degree of utilization of pelagic forms in realistic 

 terms, but obviously only a small percentage of 

 the biological potential of pelagic fishes is being 

 utilized, perhaps less than 5 per cent. 



Of the major shellfish and invertebrates, clams 

 have been Uttle touched. Oyster stocks are under 

 considerable pressure, but shrimp, despite very 

 strong market demands, are still capable of sup- 

 porting much greater production. 



If we look beyond present forms of fish 

 considered marketable and present areas con- 

 sidered capable of supporting economically profit- 

 able operations, the following considerations are 

 relevant. Most of the world catch of marine fish 

 comes from waters over the Continental Shelf at 

 depths less than 200 fathoms. Only about eight 

 per cent of the surface area's of the oceans may be 

 classified as shelf areas. The remaining 92 per cent 

 encompasses the continental slopes and deep basin 

 regions. It is estimated by Bogdanov (1966) that 

 about 90 per cent of the world's catch is taken 



from the small area defined as continental shelf 

 waters. As might be expected, on economic 

 grounds, man's fishing efforts are centered on 

 regions which are most accessible and where 

 environmental conditions operate to concentrate 

 fish. 



On a per unit basis, waters beyond the shelf are 

 producing only one-eightieth as much as the shelf 

 waters. The productivity of mid-ocean waters, at 

 least of the forms now most useful to man, would 

 be expected to be lower than over the shelf, of 

 course. Very large parts of the high seas have 

 primary productivity less than one-fifth that of the 

 present fishing areas, and in many cases it is less 

 than one-tenth. No primary production occurs 

 below a depth of about 150 meters. Nevertheless, 

 the degree of utilization in the open oceans is even 

 smaller than the expected availabiUty of fish. 



There are great quantities of squid, lantern 

 fishes, pomfrets, bristle mouth, jacks, tuna-like 

 fishes, etc., which inhabit open ocean regions, but 

 effective utilization of many of these will call for 

 development of new harvesting technology. Per- 

 haps as much as 40 to 60 per cent of estimated 

 biological potential is tied up in fish and shellfish 

 inhabiting the open oceans. If fishing systems were 

 stabilized at present efficiency levels there would 

 be Uttle hope of really major increases in the 

 harvest of pelagic fishes in the open oceans (and of 

 some pelagic forms which overlie the shelf as well). 

 There are, however, some underutilized and un- 

 used fish stocks which are available for harvest 

 with conventional gears. Such potentials are avail- 

 able in varying degree in almost all areas of the 

 world. 



Present knowledge is admittedly not very defin- 

 itive as to the areas and resources that will supply 

 future catches. At the moment it seems likely that 

 continued fisheries growth over the next decade 

 will come largely from continued geographic ex- 

 pansion. Production will increase in the Southern 

 Hemisphere as a result of greater efforts to utilize 

 the hakes and sardine-like fish off Africa and the 

 East and West coasts of South America, and 

 pelagic fishes off New Zealand and Australia. 



There will be some expansion in demersal 

 fisheries from these same waters, but the increase, 

 relative to current production, will not be large. In 

 the Indian Ocean (Arabian Sea) there is apparently 



VII-14 



