Bolz and Burns: Age and growth of larval Clupea harengus 



389 



growth increments were counted from the image pro- 

 jected by a drawing tube onto a Hewlett-Packard 

 graphics tablet interfaced with an HP-87 microcom- 

 puter. All counts were made at a magnification of 

 800x. Three counts were made on one sagitta from 

 each larva, and those otoliths with a repeatable in- 

 crement count of >90% were used in the growth 

 analysis. The other sagitta was counted once for com- 

 parison. Campana et al. ( 1987) found that detection 

 of increments during the first 15-20 days posthatch 

 are probably too fine to be resolved. In a previous 

 study by Lough et al. (1982), it was found that the 

 mean age of a 3-increment larva was approximately 

 22 d; consequently, a correction factor of 19 was added 



to the number of increments recorded in order to es- 

 tablish each larva's estimated age in days from hatch 

 (Stevenson et al., 1989; Townsend et al., 1989). Mea- 

 surements of the anterior-posterior diameters 

 (otolith length) of the sagittae and the lapilli were 

 made to the nearest micron. 



Results 



Larval herring growth 



Otoliths were dissected, mounted, and analyzed for 

 a combined total of 1,746 larval herring. Growth with 



