NOTE Anderl et al Is the first annulus missing on the otolith of Pleurogrammus monopterygius? 



167 



ertheless, it appears evident that translucent-zone 

 formation (stage 1 ) is most common in late winter to 

 spring. 



Comparisons of larval and adult otoliths 



The increase in size between otoliths of spring- 

 caught larvae and otoliths of adults with at least 

 one translucent zone suggests that the first trans- 

 lucent zone is formed considerably later than the 

 first April after fall hatching. Because study on 

 the marginal increment identified late winter to 

 spring as seasons of translucent-zone formation, 

 it appears that the first translucent-zone is prob- 

 ably formed during the fish's second spring (af- 

 ter two winter seasons). Results from the daily 

 increment counts did not conclusively support our 

 hypothesis. Some support may be gleaned from 

 the deposition pattern of the otolith daily incre- 

 ments viewed with light and SEM micrography 

 where two regions of narrow increments were 

 observed between the otolith core and the first 

 translucent zone, suggesting two periods of slow 

 growth, probably during the first two winters. 



Seasonal length data 



Seasonal larval length frequencies from FOCI 

 data and Gorbunova (1962) were very similar, 

 suggesting that the growth characteristics of the 

 Kamchatka Atka mackerel do not differ greatly 

 from those of the Northeastern Pacific fish dur- 

 ing the first nine months of life. Therefore it 

 would seem that length at age in the early years 

 should be similar between Atka mackerel from 

 the two regions. 



When seasonal lengths from FOCI, NRIFSF 

 larval surveys, and the AFSC-RACE summer 

 bottom trawl survey are combined (Fig. 5), it be- 

 comes very apparent that spring-captured Atka 

 mackerel at lengths of 180 mm FL (the smallest 

 fish observed with a translucent zone) must have 

 already lived through two winters, further support- 



Figure 3 



The following SEM micrographs were taken along frontal 

 sections of otoliths with two translucent zones that came 

 from fish 250 mm-280 mm FL captured during summer bot- 

 tom trawls in 1991. (A) This panel shows a zone of very nar- 

 row increments surrounding the otolith core. Increments 

 radiating from several accessory primordia are clearly evi- 

 dent. (B) Well-defined increments are observed with regu- 

 lar periodicity in the opaque zone proximal to the first trans- 

 lucent zone. (C) The increments narrow in width until they 

 become obscure and disappear into the groove structure that 

 is the first translucent zone. Bars = 50 /jm. 



ing the hypothesis of a missing first-year translucent 

 zone. 



The various sites where Atka mackerel were found 

 may provide clues to the early life history of this spe- 

 cies. Life history changes, such as metamorphosis or 



lift W '.'i 







