BOLZ AND LOUGH: GROWTH OF ATLANTIC COD AND HADDOCK 



JZ 

 -P 



cn 



c 



X) 

 L. 

 O 



"D 



C 



o 

 -p 

 cn 



200.0 



100.0 -■ 



50.0 -■ 



25. -- 



12.0 



-Q 0088R 



ln(L) = 1. 1987 + 4.8438(1 - g " ) 



-I — I — ^- 



-I — \ — U 



4 — I — U 



J I \ L 



J I L 



25 



50 



75 



100 



125 



150 



175 



AgG in Days 



Figure 2. — Gompertz growth curve and equation fitted to plot of In standard length and number of otolith increments (estimated age 



in days) for 189 larval and juvenile haddock collected on Georges Bank. 



L = 738.0(1 - e-0.3763[(fl+D)/365-0.1649])^ (2) 



where D = Julian date of hatch. 



Based on the 1981 season, an average hatch-date 

 of 15 April {D = 105) was employed in the present 

 model. An average length of 19.9 cm would have 

 been attained on 1 January, by fisheries science 

 convention the date at which an individual is con- 

 sidered to be 1-year-old. 



The predicted hatch-length of 4.02 mm was 

 within known limits (Colton and Marak 1969). 

 The average growth rate of 0.21 mm/day (Table 3) 

 through the first month was slightly lower than 

 that of haddock, which is consistent with previous 

 findings (Bolz and Lough 1983). At approxi- 

 mately 192 days the larval and juvenile growth 

 curve intersected the von Bertalanffy curve calcu- 

 lated for adult Atlantic cod by Penttila and Gif- 

 ford (1976): 



Atlantic Cod Larval and 

 Juvenile Growth 



Although there were few larger individuals 

 amongst the 157 larval and juvenile Atlantic cod 

 examined, the apparent pattern was similar to 

 that seen in haddock. A Gompertz growth curve 

 also provided a good fit when the natural log of 

 standard length (range: 4.6-104 mm) was plotted 

 (Fig. 4) against age in days (range: 7-151): 



ln(L) = 1.3915 + 6.2707(1 - e-o.oo53/?)_ 



(3) 



L = 1481 0(1 - e-01200((i?+D)/365-0.6160)^ (4) 



For purposes of the model a mean hatch-date of 15 

 March (D = 74) was assumed. An average At- 

 lantic cod would be expected to have achieved a 

 length of 26.1 cm by 1 January (Fig. 5). 



Predictability 



Since it is desirable, especially during field sur- 

 veys when direct analysis of otoliths is impossi- 

 ble, to be able to predict age from a given length, 



227 



