O'Farrell and Larson: Year-class formation in Clupea palllasi 



133 



For fishes aged greater than 100 days: 



N = N - 



■"100 „-0.016la-100l 



(2) 



Combining the results of Equations 1 and 2 produced the 

 mortality-corrected spawning-date distributions. 



Growth 



To evaluate correlates of both inter- and intra-annual 

 variation in survival to the juvenile stage, we wanted to 

 compare growth rates of herring up to the juvenile stage. 

 However, because it was apparent that growth rates may 

 have differed for specimens spawned at different times of 

 the year, either a linear or nonlinear growth curve fitted 

 to size-at-age data would be erroneous (O'Farrell, 2001). 

 Larger (older) and smaller (younger) individuals would 

 have experienced different growth histories; therefore a 

 plot of size versus age for any sample of fish would not 

 reflect the growth history of any one cohort. Further- 

 more, consecutive samples rarely contained individuals 

 from any given cohort because older juveniles appeared 

 to leave San Francisco Bay. Finally, we did not have 

 data on size at age of larvae; therefore growth curves 

 would be incomplete. 



Instead, we used age at size to compare growth with- 

 in and between years. To do this, we computed the num- 



ber of otolith increments (days after yolksac absorption) 

 present in fish between 40 mm and 50 mm standard 

 length. This size group was chosen to analyze growth 

 because it was well represented in both in the 1998-99 

 and 1999-2000 spawning seasons. The mean and stan- 



