224 



Fishery Bulletin 90(2). 1992 



100 



80 



□ 60 - 



40 - 



Jan March May 



Month 



Figure 9 



Percentage of Lophius americanus vertebrae having a 

 marginal width less than one ocular unit by month. Number 

 of vertebrae examined is indicated. No vertebrae were col- 

 lected during June. 



The regression of vertebral radius (VR) on TL re- 

 vealed a strong linear relationship between the two 

 variables. The regression equation based on 682 

 vertebrae from both sexes was as follows: 



TL = 11.077(VR) + 40.018 (r2 0.97). 



This indicates that growth of vertebrae is proportional 

 to growth of the fish, thereby satisfying the second 

 criterion. 



Monthly mean marginal increments were plotted for 

 all age groups combined (Fig. 8). Sample size was not 

 large enough to plot the age-groups separately. How- 

 ever, inspection of the data indicated that the seasonal 

 progression of marginal increment was similar for all 

 age-groups. Percentage of vertebrae showing a very 

 small marginal increment (less than 1 ocular unit), in- 

 dicating that little or no growth had occurred since the 

 annulus was deposited, was also plotted (Fig. 9). The 

 annuli were found to be closest to the edge of the 

 vertebrae in May. Marginal increments were highest 

 in December-February, following a period of growth 

 during July-December. The percent of vertebrae with 

 thin margins showed less variation than marginal in- 

 crements. The percent was highest in May and de- 

 creased as the season progressed. These plots indicate 

 that May is the time of annulus formation, and only 

 one checkmark is formed per year. This appears to 

 fulfill the third criterion that states that growth checks 

 must be formed at approximately the same time each 

 year; however, because data were pooled from several 

 years, this cannot be stated with certainty. Although 

 there was a decrease in the marginal increment from 

 February to March, there was no corresponding rise 

 in the percentage of very small margins (i.e., the mean 



10 12 



10 12 



Age (yrs) 



Figure 10 



Mean observed lengths-at-age for Lophius americanus. 

 Vertical bars indicate ranges of total length observed for 

 each age. Sample sizes are indicated. 



value of marginal width was not lowered by the pres- 

 ence of marginal widths < 1). Although the relatively 

 small sample sizes preclude making definitive conclu- 

 sions, these data suggest that some process is causing 



