The annual occurrence of age marks in pilchards of juvenile age had 

 been proved in the follo"King wayl/: A stratified random samgle of scales 

 was prepared to represent equally all the months of the year. The labels 

 on the slides vrcro then masked, the slides mixed, and the scales examined 

 and measured vifithout Icno'i/ledge of the size' of th.i fish or the time of year 

 collected. ViTien the measurements thus obtained vere collated, it uas found 

 that the marginal increment vras narrov.'er at one season — the apring—than 

 at any other, and increased in width during the remainder of the year. Its 

 groi/rt-h was rapid in spring and early summer follo;/ing the formation of the 

 annulus in the i.'inter, and slight from late sumracr to v/inter. 



The foregoing demonstration was possible because young pilchards are 

 available near shore in California throughout the year and aru taken by 

 the bait fisheries. "Adult'' pilchards, on the other hand,, arc migratory, 

 departing for thuir spai/ming pilace at the time of maturity, in the spring, 

 and not reappearing until raid-summer. Hence, the commercial fishery for 

 adults is seasonal, and the scale material collected for this study does 

 not include an important period of the year's groirth. Despite this hiatus 

 in data, thu results aiscussed on pages 9ff and given gr^iphically in figure S, 

 indicate, as far as they go, that in adults, as in the young, the annulus 

 appears during one season of the year — the winter, and that the marginal 

 increment increases in width until the next annulus is formed. 



For critical proof of the valid:j.ty of scale reading, the annual groivth 

 increments on the scales were studied in search of peculiarities in dimen- 

 sions, marks or other- Irregularities associated consistently with certain 

 year classes such as Lea had discovered for th^ Nor^vegian herring (Lea 1919). 

 To provide homogeneous data, an effort v;as made to select scales consistently 

 from the same part of the body, namely the side, near the tip of the pectoral 

 fin. Unfortunately such selection vras unfeasible -viti inever the fish sampled 

 were in poor condition. Under these circumstances, scales were taken v/-herever 

 they could be found, often from the back or near the caudal peduncle, where 

 pilchard scales are characteristically smaller than elsewhere » For adjust- 

 ment to a common basis to permit comparative studies, therefore, scale mea- 

 surements were translated into terms of body length of the fish, by means 

 of Lea's formulae: 



^n ^n 



3- = pT- , and (1) 



^n - ^n-1 = "^n (2) 



Tifhere s^ is the distance from the center of the scale to a particular annulus, 

 n; S the distance from the center of tht; scal^j to the edge of the scale; 

 fn the length of the fish at the time the annulus n was formed; F the length 

 of the fish at the time of the observation; t^ the growth increment in the 

 year preceding the time the annulus n was formed. Hence, t =• f, ; ^2 = ^2~^\> 

 etc. The symbol "f" is the same as Lea's "1"; it abbreviates the term "fish 

 length" as "s" does "scale length". 



T7~~ 



-' I'.alford and Uoshcr, I9I43. 



108 



