HALES: ROUND SCAD IN THE SOUTH ATLANTIC BIGHT 



Figure 8.— Scanning electron micrograph of a sagittal section through the primordium of a lapillus 

 oiDecapterus punctatus. P is the primordium and crosshatches denote daily increments. The pattern 

 of otolith growth of juveniles was consistent in most otoliths. 



to approximately increment 100, then gradually 

 became thinner and more difficult to count. Growth 

 interruptions appeared in outer portions of otoliths 

 of large fish, and growth records were more irreg- 

 ular. 



Round scad grew rapidly for 120-150 days until 

 reaching sexual maturity at approximately 110 mm 

 FL (Fig. 9). The von Bertalanffy [FL = 161 (1 - 

 exp (-0.012 (age - 29.5)))] and Gompertz [FL = 

 1.17 exp [4.76 (1 - g- 0.026 (age)) jj g^wth equations 

 provided good and nearly identical fits (r^ = 0.96 

 and 0.97, respectively) to the observed data. Specific 

 growth rates (Table 9) for juveniles were initially 

 high, decreased sharply until sexual maturity, then 

 decreased more gradually throughout the time 

 period for which age determination was possible. 

 The largest specimen for which reliable counts 

 could be determined was 143 mm FL, although 

 most specimens at that size could not be assigned 

 an age. 



The age of round scad for the entire size range 

 (FL up to 21 cm) that was collected in the South 



E 

 E. 



X 



t- 

 o 



z 



LU 



_l 



CO 



o 



160 



120 



80 



40 - 



FL = 161 (1 - exp 1 -0.012 (age - 24.3)]} 



— FL = 1.17 exp (4.76 [1 - exp (-0,026 * age)]) 



50 



100 



150 



200 



250 



AGE(d) 



Figure 9.— Von Bertalanffy (thin line) and Gompertz (heavy line) 

 growth equations. Sexual maturity of Decapterus punctatus is 

 reached at approximately 110 mm FL in 120-150 days. 



Atlantic Bight could not be determined from daily 

 increments on the lapillus. The age of all specimens 

 <120 mm FL could be determined, but only half of 



261 



