316 



Fishery Bulletin 97(2), 1999 



90 



Melanogrammus aeglefimis 



60  



30 



90 1 



90 1 



60 



30 



1991 



1 1 1 1 1 



50 100 150 



;^ 



1993 



Pollachius virens 



Age (days) 



50 100 150 



Age (days) 



Figure 6 



Estimated age versus length for larval and juvenile pollock and had- 

 dock. Lines were fitted by using the Laird-Gompertz growth model. 

 Parameters of the model are shown in Table 5. 



from the predicted length at hatching throughout the 

 size range of larvae and juvenile collected. Otolith 

 growth increments are suitable for estimating age, 

 and the analysis of length-age data for young had- 

 dock and pollock on Emerald and Sable Island Banks 

 suggests that the growth rate increases sharply at 

 the transition from a pelagic to demersal life stage. 

 Thus, pelagic and early demersal growth likely rep- 

 resents distinct "stanzas" in the growth history of 

 these gadoids, and these "stanzas" may have differ- 

 ent effects on recruitment variability. Rapid juvenile 

 growth may increase juvenile survivorship by de- 

 creasing the time during which juvenile are exposed 

 to predators (Houde, 1987). Interannual variation in 

 juvenile growth rates may influence interannual 

 variation in juvenile survivorship. Additional com- 

 plicating factors during the pelagic phase of juvenile 



fish, such as different residence times and diel mi- 

 grations in the water column (Koeller et al., 1986), 

 reduce the possibility of identifmg correlations be- 

 tween interannual variation in growth rates and 

 environmental factors, and thereby allow predictions 

 of recruitment success. 



Acknowledgments 



This study was supported by funding from the Natu- 

 ral Sciences and Engineering Research Council of 

 Canada (NSERC) to the Ocean Production Enhance- 

 ment Network (OPEN) program. Support from 

 Instituto Politecnico Nacional, COFAA, and CoNaCyT- 

 Mexico was also provided to the author. I am most 

 grateful to numerous colleagues from Dalhousie, 



