Miller et al.: Relation between otolith size and larval size at hatching for Gadus morhua 



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Radius of laplllus at hatching (|im) 



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Figure 7 



Relation between the residuals from mean SL and mean water tem- 

 perature at collection and (A) the area of the lapillus (LA) and (B) the 

 lapillar radius at hatching (LR) for newly hatched cod larvae on the 

 Scotian Shelf Shown on each plot are the predicted linear relation- 

 ships and 95'7f confidence intervals of the mean and of individual pre- 

 dictions. Regression relationships are Residual = 0.00021 (±0.00027) x 

 LA - 0.102 (± 0.143), n = 37, r- = 0.01, P = 0.89; and Residual = 0.013 

 (±0..21) X i,fl- 0.184 (±0.28), /! =37.;-'- = 0.001, P = 0.85. 



The implications from our results for studies on 

 other species are less clear It is important to note 

 that one would not expect all species to exhibit the 

 same plasticity in size at hatching, or in the rela- 

 tionship between fish size and otolith size at hatch- 

 ing. Hence, for some species there is little variation 

 in initial size at hatching. In these species the error 

 introduced by assuming a single, universal size at 

 : hatching is probably small. However, it is important 

 to recognize that back-calculation techniques all as- 



sume a common origin for the family of size-at-age 

 lines that are modeled. The methods differ only in 

 the definition of the origin (fish size at zero otolith 

 size, biological intercept, or otolith size at zero fish 

 size), but all assume a single value. Indeed Campana 

 ( 1990) noted that relatively little attention had been 

 paid to the effects of variation in the intercept term 

 of back-calculation methods; most attention had been 

 paid to variation in the slope. However, for species 

 that are known to vary widely in hatching size (e.g. 



