Structiire of the recrtiitment diagramo - The diagram reads from bottom 

 to top, beginning with the production~of~eggs within the female and iead= 

 ing through successive stages to net recruitment at the topo At the left 

 are variables pertaining to population densities (intrinsic inflaences)^ 

 and in the middle are the survival rates (dependent variables) upon which 

 the two categories of influences (independent variables) operate to affect 

 the recruitmento Algebraic notations relate equivalents o Thus the frae-= 

 tion "number of eggs hatched** over "number of eggs spawned" equals the 

 "egg survival rate", and the ''number of eggs hatched" also equals the "den= 

 sity of larvae", at least initiallye Correlation notations are given as 

 arrows pointing from tha independent to the dependent Tariabie with a sign 

 to indicate whether the correlation should be negative or positive.? and 

 where inde terminates, ioe,, depending on the way the independent variable 

 is expressed;, the plus=minus sign (=) is usedo 



Discussion of the recraitment diagram ,, - It is not intended that the 

 recruTTment diagram should be an outline of precedure. Rather it indicates 

 a complex of relationships too extensive and inclusive of too many subjects 

 ■apon which data are, for the most partj non-sxistent at present and diffi = 

 cult to obtain in the fut'ureo It illustrates tha manifold phases of the 

 recruitment problem and should serve as a reminder of the fragmentary nature 

 of less comprehensive treatanentSo 



This commentj however^ should not discourage effort to solve the prob- 

 lem of recruitment by some less comprehensive or abbreviated process,, If 

 the survival rate in certain stages of life is relatively constant from 

 year to year these stages can, without risk, be ignored » If this be done 

 and high correlation is found, much time will have been saved. If, on the 

 other handj the results turn out to be indeterminate, it would merely mean 

 that the stages that were ignored did, infact, have variability and should 

 have been consideredo Since that requires data for which there are ccw no 

 collection facilities, we will merely have to decide between surveying 

 the significance of available data or neglecting themo It is clear, how^ 

 ever, that a program for determining additional aspects of certain reproduc= 

 tire attributes of the pilchard population and also of oceanographic con= 

 ditions, including study of that portion of the marine fauna which may 

 exert predation on any stage of the pilchard, should be started at the 

 earliest opportunity.) 



Discussion of an abbreviated recruitment analysis » - It is interest- 

 ing to speculate on how limited a view would have to be taken if one were 

 confined to data already available or in process of becoming available o 

 The diagram opposite gives a scheme of correlation analysis on what 

 appears to be fairly reasonable grounds » It ignores intra-ovarian, and 

 eggs, mortalityo Such sampling of eggs on the spaTming grounds as has been 

 made is impressive in the relative constancy of the numbers found and fails 

 to suggest important variability in survivaio 



The scheme includes only the oceanographic extrinsic variable affect= 

 ing larval survival because it hardly seems that competition between 



