Quinonez-Velazquez: Age validation and growth of Melanogrammus aeglefinus and Pollachius virens 



313 



B 



^Pp i^ 



YS 



X 



Figure 4 



Light micrographs of sagittae showing different landmark checks. (A) Sagitta from a 

 13.7-mm-SL, 37-day-old haddock. (B) Sagitta from a 12.4-mm-SL, 50-day-old pollock 

 N = nuclear check, H = check at hatching, and YS = yolksac check. Bar of photograph 

 represents 10 |am. 



around the nucleus. It was the first mark presented 

 in larval otoliths (Bolz and Lough, 1983; Radtke and 

 Waiwood, 1980; Campana. 1989). Outside the 

 nucleus, four to eight irregularly spaced increments 

 were bounded by a discontinuous zone which ap- 

 peared to be the yolksac check (Bolz and Lough, 

 1983). Laurence ( 1974) reported that at 7^C yolksac 

 exhaustion occurs 6-7 d after hatching for haddock, 

 and Fridgeirsson (1978) observed that at 7.2°C 



yolksac exhaustion occurs within 6 d for haddock 

 larvae and 8 d for pollock larvae. From the regres- 

 sion of larval length to sagittal diameter, I estimated 

 that yolksac resorption occurs at a standard length 

 of 5.0 mm in haddock (at 3.5°C) and 5.1 mm in pol- 

 lock larvae (at 5.0°C), corresponding to a mean age 

 of 9 and 5 d, respectively. Fridgeirsson ( 1978) reported 

 that haddock start independent feeding at 6-10 d 

 after hatching and pollock at 8-10 d after hatching. 



