ARE THE WORLD-WIDE DECLINES IN SARDINE 

 CATCHES RELATED?* 



By John C. Marr and James E. Bohlke 



South Pacific Fishery Investigations, U.S. Fish and Wildlife Service 

 ^50-B Jordan Hall, Stanford, California, U.S.A. 



Large fluctuations in the catches of marine fishes, especially pelagic 

 species, have long been known and may, in a sense, be considered to 

 have given the original and major impetus to the birth and growth of 

 the science of fishery biology. Indeed, such fluctuations have been 

 observed to occur in so many different species and areas that one might 

 suppose them to be a characteristic feature of the great fisheries. It is 

 significant, however, that fishery biologists are not in general agreement 

 as to the causes of these fluctuations. 



Recently there have been major declines in the catches of some of 

 the sardines; declines which have caused great economic hardship and 

 have, at least in one instance, resulted in a greatly expanded research 

 effort (Anonymous, 1950). We refer especially to the Japanese land- 

 ings of Sardinops melanosticta, the North American landings of S. caeru- 

 lea, and the Portuguese landings of Sardina pilchardus. These landings 

 are shown in Figure 1. 



The North American data include landings in Canada and the 

 United States. Relatively small landings made in Mexico are also in- 

 cluded since 1940. It has been demonstrated (Schaefer, Sette and Marr, 

 1951) that from the inception of the fishery until 1942, the growth 

 of the fishery, as shown by the annual catches, followed a logistic curve 

 characteristic of the growth of many industries. Some of the deviations 

 about the curve are clearly related to economic conditions; the eco- 

 nomic depression of the early 1930's, for example, is reflected in the 

 reduced catches during that period. From 1934 until 1944 the annual 

 catch fluctuated around an average of about 550,000 metric tons. Fol- 

 lowing 1944 the catches have declined, in some seasons catastrophically 

 so, but with a short-lived partial recovery in 1949 and 1950. The basic 

 causes of this decline have not been completely elucidated, but the 

 major immediate causes include a series of smaller than average year- 

 classes and a probable shift in the distribution or migratory behavior 

 of the fish; the relation of an intensive fishery to these factors has not 



* Published by permission of the Director, U.S. Fish and Wildlife Service. 



183 



