range much too great for comfort in view of the and Edwards 1962, Meseck 1962, Schaefer 1965, 

 pressing need for protein foods and the urgency of Alverson 1965). As the Graham and Edwards 

 fishery management and development problems, estimate involves only bony fishes, a comparable 

 If, however, these yield forecasts are examined in figure based on their techniques would be some- 

 light of the methods and assumptions which what higher. A mean value for these estimates 

 various authors have employed, the range (55 to would be about 85 miUion metric tons. 

 2,000 million metric tons) is understandable and. Those scientists who have based their analyses 

 to a degree, reconcilable. It is necessary, first, to on theoretical energy flow through the food chain 

 distinguish between production and yield. Produc- show estimates on the high side of the projected 

 tion is the total product of the biological activity total yield. There are some obvious reasons why 

 including some that is taken by non-human preda- these projections or estimates would be higher 

 tors. In no case is primary production fuUy than those based on past catch patterns. Several of 

 harvestable. Table 1 provides specific estimates of the authors have, in fact, estimated the biological 

 world marine fish and shellfish potential by potentialities of the system; they estimate total 

 various authors, the year the forecast was made, gross production at some stated trophic level 

 and the technique employed in making the esti- independent of physical and/or economic capa- 

 mate. Several estimates are given for some authors bility by man to intervene. Thus, Chapman's 

 who employed several techniques and various 2,000 million metric tons represents theoretical 

 assumptions in their forecasts. Where multiple total available biological production, as does Pike 

 values are given the underlined figure is the one and Spilhaus's 1 80 to 1 ,400 million metric tons, 

 commonly attributed to the author. When realistic limitations based on technological 

 Examination of Table 1 brings out certain capabilities and human tastes and preferences are 

 relationships among %ese estimates. Those based imposed, the figures are much lower (e.g., Schaefer 

 on extrapolation frt.m existing catch or fishing 200, Pike and Spilhaus 200, Bogdanov 80 and 

 patterns give values at the low end, ranging from Graham and Edwards 60 million metric tons). If 

 50 to 160 million metric tons (Firm 1960, Graham one adds to Graham and Edwards' figure other 



Table 1 

 ESTIMATES OF TOTAL OCEAN YIELDS OF AQUATIC ANIMALS 



^°''^^^^^ Year Method Author 

 (million metric tons) 



21.6 1949 ext.' Thompson 



55.4 1955 ext. FAQ 



50 to 60 1960 ext. Finn 



55 (bony fishes) 1962 ext. Graham 8( Edwards 



55 (by 1970) 1962 ext. Meseck 



^(bony fishes) 1962 ext. mf.^ Graham & Edwards 



66 (by 1970) 1965 ext. Schaefer 



70 (by 1980) 1962 ext. Meseck 



60 to 80 1965 ext. Alverson 



70 to 80 1965 ext. ef. Bogdanov 



115 (bony fishes) 1962 mf. Graham & Edwards 



160 1965 ext. Schaefer 



200 1965 mf. Schaefer 



200 1965 mf. Pike & Spilhaus 



1,000 1966 mf. Chapman 



180 to 1,400 1962 mf. Pike & Spilhaus 



2,000 1965 mf^ Chapman 



Source; Schaefer and Alverson (1968). 

 ext. = Extrapolated from catch trends or existing knowledge of world fish resources. 



2 



mf. = Energy flow through food chain. 



VII- 10 



