HISTORICAL TRENDS AND STATISTICS OF THE 

 SOUTHERN OSCILLATION, EL NINO, AND INDONESIAN DROUGHTS 



William H. Quinn, David O. Zopf. Kent S. Short, and Richard T. W. Kuo Yang' 



ABSTRACT 



A 116-yr Southern Oscillation index record was used in conjunction with environmental data and 

 reports from various authors on disturbances to the anchoveta fishery, marine bird life, etc. off the 

 Peruvian coast, to infer the occurrence of past El Nino type events and their intensities. The resulting 

 long time history substantiates our earlier report that certain Southern Oscillation index features are 

 excellent precursors of subsequent El Nino type events. We suggest that statistics derived from this 

 time history could be useful in the management of the Peruvian anchoveta fishery and for providing 

 long-range outlooks on El Nino type activity. 



Anomalously heavy precipitation in the central and western equatorial Pacific and Indonesian 

 droughts were closely associated with El Nino type events. 



In recent years the world demand for fishmeal has 

 continued to increase, as has the world population. 

 The Peruvian anchoveta fishery, which ordinarily 

 provides over half the world's supply of fishmeal, 

 has become a critical resource; and anything that 

 affects the output of this fishery is of world-wide 

 significance. Johnson and Seckel (1977) reported 

 that the catch in this fishery declined from a high 

 of over 12 million tons (about V.-> of the total world 

 catch of all fish) in 1970 to about 2 million tons in 

 1973. Although overfishing in 1970-71 may have 

 contributed heavily to this decrease in anchovy 

 catch, the strong El Nino of 1972-73 was undoubt- 

 edly also a major cause for the precipitous decline 

 in catch (Figure 1). However, the 1975 catch was 

 still only about 257c of the record 1970 catch, the 

 1976 catch remained low, and the target for 1977 

 has now been reduced to 2 million tons of an- 

 choveta and other fish such as sardines and hake. 

 Apparently the unfavorable environmental condi- 

 tions caused by the very weak event of early 1975 

 and the moderate El Nino of 1976-77 have not only 

 contributed to the delay in recuperation of the 

 fishery, but also are causing a further degradation 

 of it. In early October 1977 the Fisheries Ministry 

 of Peru said (according to a Reuters wire service 

 report) that the stocks were believed to be so low 

 that the anchoveta fishing, which was suspended 

 in May 1977, would not resume until the second 

 half of 1978. 



'School of Oceanography, Oregon State University, Corvallis, 

 OR 97331. 



Statistical information pertaining to the histor- 

 ical occurrence of El Nino type events is presented 

 to: 1) aid in long-term fishery assessment (Peru- 

 vian anchoveta fishery); 2) provide a basis for 

 speculative long-range outlooks on event occur- 

 rence (beyond a year in advance); and 3) guide 

 long-range predictions ( 1-12 mo in advance). Rela- 

 tionships between El Nino type events. Southern 

 Oscillation index trends, index component trends, 

 and Indonesian droughts are shown and discussed. 



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1975 



Manuscript accepted January 1978. 

 FISHERY BULLETIN: VOL. 76, NO. 3. 1978. 



Figure l. — The Peruvian anchovy catch for the period 1962-76 

 as obtained from the Industrial Fishery Products Market Review 

 and Outlook for June 1977 'National Marine Fisheries Service 

 19771. The 1976 figure is a preliminary value. The 1977 figure is 

 the Peruvian Fishery Ministry target value for anchovies and 

 other species such as sardine and hake, as reported by Reuters 

 wire service on 19 October 1977. 



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