BIOLOGY OF THE ATLANTIC MACKEREL 



J 57 



Moore (loc. fit.) has shown that there are successive batches of eggs ripened by 

 an individual female during the course of the season. This introduces the uncertainty 

 as to whether any particular enumeration has included, on the one hand, all batches 

 destined to be spawned dining the ciurent season and, on the other hand, none that 

 were destined to be spawned during a following season. The difficulty of making a 

 correct decision is amply portrayed by the thorough study by Clark (1934) on the 

 California sardine, Sardinops caerulca, a species which, like the mackerel, spawns 

 successive batches. Clearly this subject requires additional study to provide statisti- 



80 



a 



<60 



x 



Ul 



K 

 £40 



20 



20 



8 



=f" 



YEARLINGS- 



P*W 



TWO 

 YEAR 

 OLDS 



6 



40 



20 



22 



26 



28 30 32 34 



LENGTH, CENTIMETERS 



36 



40 



OVER 

 40 



9 



10 



! I 



14 



12 13 



LENGTH, INCHES 



Figure 2.— Length and age at which mackerel reach reproductive maturity. The upper panel shows, by 2H cm. length groups, 

 the percentage of each sex matured. The lower part shows by half cm. length groups, the numbers examined for determina- 

 tion of percentage of maturity. 



cally adequate data, and deserves such study because the ability to compute the num- 

 ber of eggs that can be produced by a population of known size-composition or, con- 

 versely, to compute the size of a parent population of known size-composition from the 

 known numbers of eggs found in a spawning area would provide useful, if not indis- 

 pensable, data for elucidating several perplexing problems connected with the fluctua- 

 tions of fish populations and the management of fish resources. See pages 164 and 

 165 for an example of the uses of such data. 



