1 ho 



Fishery Bulletin 94(1), 1996 



habitat changes, have been associated with acces- 

 sory primordia formation in the otoliths of other fish 

 species (Gartner, 1991; Sogard, 1991; Toole et al., 

 1993 ). Atka mackerel accessory primordia were found 

 proximal to the first translucent zone in adult otoliths 

 but none were observed in larval otoliths, suggest- 

 ing that these structures were formed after their first 

 April and before the following spring. The appear- 



ance of the accessory primordia coincides with a time 

 in the life history of Atka mackerel when young fish 

 may be undergoing migration and habitat changes 

 within the water column. Catch data from the three 

 scientific surveys described in this study seemed to 

 indicate that Atka mackerel migrate from nearshore 

 surface waters, where larvae are found between fall 

 hatching and the following spring, to offshore sur- 



Larval Atka mackerel 



o 



Aug 



Month 



Figure 4 



Comparison between the average monthly length of larval Atka mackerel collected 

 from the northeastern Pacific Ocean (FOCI) and the monthly midpoint of the larval 

 length range from northwestern Pacific Ocean Atka mackerel (Gorbunova, 1962) 



400 



300 



~ 250 



E 



E 



£ 200 

 o> 



c 

 <b 

 _1 



150 



-FOCI 



NRIFSF 

 -AFSC RACE 



D 



o smallest fish with 1 observed otolith translucent zone 



100 



Isl translucent zone formation 



JAN JUL JAN JUL JAN JUL 



Month 



Figure 5 



Combined average seasonal lengths of Atka mackerel larvae collected from nearshore surface waters from Sep- 

 tember to June 1977-86 by FOCI and of young fish collected both from offshore larval surface tows from June to 

 August 1991 by NRIFSF and from the 1991 nearshore summer bottom trawls ( 100-200 meters) by AFSC-RACE 

 scientists. The smallest fish (180 mm FL) observed with a single translucent zone were captured in May from 

 nearshore bottom trawls. FOCI = Fisheries-Oceanography Coordinated Investigations; NRIFSF = National Re- 

 search Institute of Far Seas Fisheries; AFSC-RACE = Alaska Fisheries Science Center's Resource Assessment 

 and Conservation Engineering division. 



