DYNAMICS OF CERTAIN NORTH SEA FISH POPULATIONS 245 



itself become possible through a true increase in the size of the population 

 resulting from the very large influx of young fish that is known from age 

 composition data to have occurred since the war, starting with the very large 

 year-class born in 1947. Although the data do not exist that would enable 



1905 



TURBOT 



PLAICE 



HADDOCK 



1913 1920 



1930 1938 1946 1950 



-^Yea^s 



Fig. 2.— Data of total landings of Fig. i, expressed as logarithms of ratio (x lo) of mean value 



1906-57, for each species. 



events before the last war to be examined in this way, it seems difficult to 

 escape the conclusion that the sole population has indeed been increasing 

 throughout the century. If the increase continues at the same rate the sole 

 population of the North Sea will, in some twenty or thirty years' time, 



