SECT. 3] EASTERN BOUNDARY CURRENTS 277 



depth), a condition essential for maximal development of phytoplankton 

 populations (Sverdrup, 1953). 



Quantitative studies of the rate of production of organic matter in the oceans 

 by the carbon- 14 method have been reported by Steeman Nielsen and Jensen 

 (1957). Over large parts of the ocean the average rate of carbon fixation was 

 found to be less than 0.2 g C/m 2 /day. In the regions of eastern boundary currents 

 the following ranges of values were measured : 



Canary Current 0.11-0.67 g C/m 2 /day 



Benguela Current 0.46-2.5 (3.8 in Walvis Bay) g C/m 2 /day 



California Current 0.24-0.9 g C/m 2 /day 



Recently on a station near the northern limits of the Peru Current, a rate of 

 1.02 g C/m 2 /day was measured (Holmes, Schaefer and Shimada, 1957). In the 

 same region extremely high values of surface chlorophyll "a" (up to 2.0 mg/m 3 ) 

 were reported. 



Standing crops of zooplankton are also large in eastern boundary current 

 regions, with values in nearshore waters as high as the maximum values in high 

 latitudes. Friedrich (1950) has prepared a chart of zooplankton concentrations 

 in the Atlantic (using Meteor and other data) on which the highest values are 

 found beyond 50°N and 50°S, and in small areas off the southwest coast of 

 Africa, with somewhat smaller values in the Canary Current. Detailed charts 

 of the zooplankton distribution in the Pacific (NORPAC Committee, 1960; 

 Holmes, Schaefer and Shimada, 1957; Reid, 1962a) show similar features, with 

 highest values beyond 40°N and 50°S and in the regions of the California 

 and Peru Currents. Extreme values of more than 1600 parts of zooplankton per 

 billion (10 9 ) parts of water are found in small areas of the Bering Sea, and the 

 California and Peru Currents, diminishing to less than 25 parts/ 10 9 over 

 most of the subtropical anticy clonic gyres. 



The principal economic value to man of these regions lies in the large mid- 

 and low-latitude concentrations of fish of commercial importance. A significant 

 element of these resources consists of clupeoid fishes with short food chains (as 

 the California sardine, and the Peruvian anchovy) and their predators (such as 

 bonita, yellowfin tuna, and cormorant and other producers of guano) (Walford, 

 1958). An impression of the magnitude of these resources can be gained from 

 estimates of the anchovy population along the Peruvian coast. During 1956 

 the production of Peruvian bird guano was approximately 330,000 tons. The 

 principal food of the guano birds is anchovy (Engraulis ringens) ; and if one 

 compares the phosphorus content of guano and of the fish (Hutchinson, 1950; 

 Goldberg, in litt.), it appears that the minimum conversion factor is about 13 

 to 1. Thus at least 4.3 x 10 6 tons of fish were consumed to produce this much 

 guano. At the same time other predators, including man, are attacking the 

 same species; and the commercial catch of anchovy in 1959 was nearly two 

 million tons (Popovici, in litt.). If one estimates that at least four million tons 

 of anchovy can be removed in a year from the inshore water of Peru, by birds 

 and man, this is equivalent to about one-seventh of the annual world landings 



