MOKSNESS and WESPESTAD: AGE AND GROWTH OF LARVAL PACIFIC HERRING 

 30 



a 



■D 



c 

 a 

 ex 



OJ 



c_ 

 Ul 



a 



20 



10 



- 



-10 



— r~ 

 10 



— r~ 

 20 



—I — 

 30 



40 



— 1 — 

 50 



— \ — 

 60 



— I 

 70 



Actual age in days 



Figure 2. — Discrepancy between estimated age (real age 

 minus estimated age) and actual age of Pacific herring as a 

 function of actual age. y = 8.3 - 0.014 x, r = 0.05. 



20 



 Age 46 days 

 o Age 62 days 



1 — I — ' — I — ' — I — < — I — ' — I — ' — I — ' — 1 — ' 

 25 35 45 55 65 75 85 95 



Standard length (mm) 



Figure 3. — Relationship between estimated age and stan- 

 dard length in Pacific herring larvae of same age. Age 46 

 days: y = 39.63 - 0.14 x. r = 0.04; age 62 days: y = 59.53 - 

 0.06 X, r = 0.27. 



fourth order polynomial, provided the best fit to 

 the initial length of the larvae. 



The average daily growth rate ( ± 1 SD) calcu- 

 lated from all otoliths with the fourth order poly- 

 nomial is presented in Figure 5 along with the 

 estimated minimum, maximum, and average 

 growth rate obtained from the hemng measured 

 at termination of the experiment. The relation- 

 ship shows that there is a high similarity in the 

 trends of the gi'owth curves between the differ- 

 ent age groups. The daily gi'owth rate calculated 

 from the standard length of the larvae at termi- 

 nation of the experiment showed an average of 

 0.66 mm/d, a minimum of 0.31 mm/d, and a max- 

 imum of 1.48 mm/d. Estimation of the average 



growth rate, using these data, gives an average 

 growth rate of 0.73 mm/d. 



DISCUSSION 



The results of this study show evidence of 

 daily increments in the otoHths of Pacific her- 

 ring, agreeing with earlier investigations on the 

 same species (McGurk 1984a). A difference of 

 eight days was observed between the estimated 



100 

 80 

 60 

 40 

 20 

 



200 400 600 



Otolith radius (jjm) 



800 



Figure 4. — Relationship between otohth radius (.x) and stan- 

 dard length (i/) of the Pacific herring larvae. A:y = 8.1461 



0.96. C: y 



r = 0.98. B: y = 2.6738 + 0.1123 x. 

 = 15.6952 * lO'"-™'" ^', r = 0.98. 



511 



