FISHERY BULLETIN: VOL. 81. NO. 4 



The otoliths were viewed and photographed with a 

 Semco Nanolab-7 SEM. 



Radtke and Waiwood (1980) have shown that cod 

 larvae shrink in length as much as 15% within 15 min 

 of death and another 5% following preservation in 

 ethanoL The amount of shrinkage was dependent on 

 the size of the larvae. In order to correct for shrink- 

 age, an algorithm developed by Theilacker (1980) for 

 estimating the differential shrinkage of northern 

 anchovy, Engraulis mordax, larvae with length was 

 applied in this study to both cod and haddock 

 larvae: 



lnL = ln^ + 0.289<r°- 434 *i*2' 



-0.680 



where L = standard length (mm) of the larvae 

 prior to death and alcohol fixation; 



X[ = standard length (mm) of the pre- 

 served specimen; and 



X, = length of handling time (min) from 

 death until preservation (assumed 

 to be about 20 min in the present 

 study). 



Although cod and haddock larvae are less fusiform in 

 shape than northern anchovy, the percentage of 

 shrinkage with length agrees closely with the findings 

 of Radtke and Waiwood (1980). It therefore 

 appeared reasonable to use Theilacker's (1980) 

 algorithm as a correction factor for the size range of 

 larvae collected in this study. All lengths referred to 

 in the results and discussion portions of this paper 

 are reported as corrected lengths unless otherwise 

 stated. 



RESULTS 



Growth of Atlantic Cod and Haddock 

 Otoliths 



The inner ear of adult teleosts contains three otoliths 

 within its membranous labyrinths: 1) The sagitta 

 located within its sacculus; 2) the lapillus housed 

 within the utriculus; and 3) the asteriscus situated 

 within the lagena. When viewed under a compound 

 microscope with transmitted light, the otoliths of cod 

 and haddock larvae were composed of a series of light 

 and dark rings (Fig. 2) which corresponds to the 

 heavily calcified incremental zones and the organic- 

 rich discontinuous zones of Watabe et al. (1982). 

 The sagittal increments (1 incremental and 1 discon- 

 tinuous zone) were segregated into three or more 

 regions delimited by distinctly thicker, darker, dis- 

 continuous zones referred to as checks or check 



rings. The innermost region or nucleus had a mean 

 diameter of 16.2 jum (SD = 2.8) in cod and 14.7 jum 

 (SD = 6.8) in haddock When viewed under SEM, the 

 nucleus was composed of a central amorphous core 

 surrounded by a more structured area in which 1 or 2 

 irregular increments (Fig. 3) were discernible in some 

 specimens. Proceeding outward from the nuclear 

 check ring were 2-8 faint increments bounded by a 

 discontinuous zone which appeared to be syn- 

 onymous with the yolk-sac check found by Radtke 

 and Waiwood (1980) in larval cod otoliths and with 

 the "first heavy ring" noted by Geffen (1982) in 

 otoliths of herring (Clupea harengus) and turbot 

 (Scophthalmus maximus). The mean diameter of the 

 area enclosed by the yolk-sac check was 27.2jU.rn (SD 

 = 3.8) in cod and 23.5 ju.m (SD = 2.8) in haddock. Be- 

 tween the yolk-sac check and the edge of the otolith 

 were an average of 8 (haddock) to 11 (cod) 

 increments of <1 jum followed by thicker rings of 

 1-3 jum. 



The sagittae and lapilli of an individual larva con- 

 tained about the same number of increments, and 

 both pairs of otoliths were present in all cod and had- 

 dock, regardless of length. In larvae < 7.0 mmSL, the 

 sagitta and lapillus were both circular with centrally 

 positioned nuclei and were of equal size. Cod larvae 

 with a 10.0 mm SL had sagittae with maximum 

 diameters 1.8 times greater than those of the lapilli, 

 and by 25.0 mm in length the difference had further 

 increased to 2.3 times (Fig. 4). The same trend was 

 evident in haddock larvae, and sagittae in larvae with 

 a 10.0 mm SL had a maximum diameter 1.5 times 

 greater than that of the lapilli. Growth of the sagitta 

 was relatively greater in the anterior- posterior plane, 

 and the otolith was oval in the larger larvae. The 

 lapillus remained roughly circular; however, deposi- 

 tion was not uniform and the nucleus became eccen- 

 tric in larger larvae (Fig. 3). 



No discernible asterisci were present in cod larvae 

 with sagittae having >37 increments. Extrapolation 

 from the plot of otolith diameter vs. standard length 

 (Fig. 4) indicated that the asteriscus first appeared 

 when the larvae reached a length of about 9.0 mm 

 Once initiated, the asteriscus grew more rapidly than 

 the lapillus and would be expected to surpass it at a 

 length of 90 mm. No asterisci were found in the had- 

 dock larvae examined. 



Atlantic Cod and Haddock 

 Larval Growth 



Figure 5 is a plot of the standard lengths (range: 7.8- 

 24.9 mm) of 99 cod larvae vs. their number of sagittal 

 increments (range: 13-66). Assuming that the num- 



830 



