THE GROWTH FORM OF POPULATIONS 



321 



it is an adaptive response to the rigors of 

 winter. For such cases the concept of mean 

 density or balance in time seems to have 

 less validity than it has for species with 

 overlapping generations. 



concludes that these data are of consider- 

 able value in that they reflect the compara- 

 tive abundance of the species, in a local 

 area at least, from year to year. He is con- 

 cerned with the course of the Miramichi 



a: 



ixl ^ 



^— </5 



o 

 UJ o 



< ^ 



(T. 

 UJ 

 Q. 



a: 



UJ 

 CD 



10.000 - 



5.000 - 



NOVEMBER 



DECEMBER JANUARY FEBRUARY MARCH : 



Fig. 114. Smoothed population trends of three arthropod species inhabiting tussocks. Dotted 

 line P. subcrassus; solid line, H. pallidulus; dash line, A. aphidioides. ( From Ford. ) 



Some valuable data on the fluctuations 

 of populations of salmon over a long period 

 of observation are reported by Huntsman 

 (1937, 1938), who comments that the 



fishery near Chatham, New Brunswick, 

 Canada, on the Atlantic Coast. 



Figure 115 plots the salmon catch and 

 mean rainfall in inches for July to August 



ii "1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ii 1 1 1 1 1 1 II 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 



1870 1880 1890 1900 1910 1920 1930 

 TIME IN YEARS 

 Fig. 115. Fluctuations of salmon populations in the Miramichi fishery, 1870 to 1936. Rainfall 

 appears at the top of the graph. ( From Huntsman. ) 



"fluctuations in fish abundance and their at Chatham from 1874 to 1936. Rainfall is 



causes is the central fisheries problem" of interest, for Huntsman beheves it is one 



(1938). There are statistics on the salmon of the most significant factors that aflFect 



catch from about 1870 on, and Huntsman the fishes when they are young and still liv- 



