BOLZ AND LOUGH: GROWTH OF ATLANTIC COD AND HADDOCK 



200 



175 



D 

 Q 



W 



CD 



<; 



25 



50 



75 



100 



— I — I — 1 I I I I I I I 



125 150 175 



Standard Length (mm) 



Figure 7. — Inverse regression of Atlantic cod growth curve with 95% confidence intervals for predicting age in days for a given 



standard length (mm). 



however, be noted that the size range available 

 for study limited the search for a settling check to 

 individuals >90 mm SL and does not preclude the 

 possibility that thinner, less discernible checks 

 may be found when greater numbers of juveniles 

 50-90 mm SL are analyzed. 



In both haddock and Atlantic cod diametral 

 growth (fjim) of the sagittae, lapilli, and asterisci 

 was linearly related to standard length (mm) 

 throughout the larval and juvenile periods. The 

 high correlation (r > 0.98) of this relationship 

 and its good agreement with measurements made 

 by Bergstad (1984) would allow the sagittal di- 

 ameter to be used as a check on the predictability 

 model outlined in Equations (5) and (6) for esti- 

 mating age from standard length. Estimated ages 

 for haddock larvae and juveniles based on maxi- 



mum otolith diameters may be obtained with the 

 following equation: 



Figure 6. — Inverse regression of haddock growth curve with 

 95% confidence intervals for predicting age in days for a given 

 standard length (mm). 



Y = 28.390 + 2.413Xi + 21.561X2 + 73.841X3 



(7) 



where Y = estimated age in days, 



Xi = sagittal diameter in mm, 

 X2 = lapillus diameter in mm, and 

 X3 = astericus diameter in mm. 



Table 6 provides a comparison of estimated ages 

 derived from otolith diameters with observed 

 ages derived from the number of daily incre- 

 ments. Although multiple regression analysis 

 using the three otolith diameters yielded a high 

 correlation coefficient (r = 0.9890) and nonsignif- 

 icant ^-values, the 95% confidence limits are 

 quite broad (±2 weeks) and should be used with 

 caution. Use of the sagittal diameter alone 

 (Y = 35.945 + 18.484Xi) provided a good fit 

 (r = 0.9861) for juveniles >90 mm SL but was a 

 poor age predictor for younger fish. If only the 

 sagitta is available for analysis, the relationship: 



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