FISHERY BULLETIN: VOL. 80, NO. 2 



In the laboratory, all fish were identified and 

 measured for standard length (SL). Both saccu- 

 lar otoliths were removed from each English 

 sole. In cases where large numbers of P. vetulus 

 were captured, individuals were selected to 

 cover the size range of the sample. The otoliths 

 were mounted on microscope slides in the syn- 

 thetic mounting medium Protexx. 



One otolith from each fish was ground on 600 

 grit carborundum paper to a thin section along a 

 sagittal plane through the nucleus. The sections 

 were examined under 250X magnification, using 

 either bright-field or polarized illumination. 

 Counts of fortnightly rings were made on each 

 otolith. No fortnightly rings could be detected in 

 the central area of the otoliths, which apparently 

 represents the time the larvae are in the plank- 

 ton. Therefore, daily rings were counted from 

 the nucleus out to the first fortnightly ring. The 

 actual age of each fish was calculated by sum- 



FlGURE 1.— The study area. Sam- 

 pling stations are indicated by the 

 letters A through G. 



ming the number of daily rings in the nuclear 

 area, the number of fortnightly rings times 14, 

 and the mean age of first ring formation, which 

 was taken to be 5 d for this species (Larocheetal. 

 1982). 



The count of rings on each otolith was repeated 

 until the same count was obtained three times. 

 As a further check on the accuracy of the counts, 

 a set of 42 otoliths was recounted several months 

 later and a mean error computed. Counts of the 

 number of daily rings between fortnightly rings 

 on 40 otoliths and the number of fortnightly 

 rings between consecutive annual rings on 15 

 otoliths from older specimens were made as tests 

 of fortnightly periodicity. 



Individual growth curves of 25 fish were back 

 calculated by making radial measurements to 

 every other fortnightly ring along the same axis 

 from the nucleus to the anterior edge of the oto- 

 lith. From these measurements and the linear 

 relationship between otolith radius and standard 

 length of the fish, 3 lengths-at-age for the various 

 points in the life of an individual were calculated. 



RESULTS 



Counts of daily rings between fortnightly rings 

 yielded a mean of 13.95 with a standard devia- 

 tion of 0.68. The mean number of fortnightly 

 rings between consecutive annual rings was 26 

 with a standard deviation of 1.13. The mean dif- 

 ference between repeated counts of fortnightly 

 rings made a substantial period of time apart 

 was 1.45 rings. Figure 2 shows the daily and fort- 



3 A regression of standard length on anterior otolith radius 

 was performed on 60 data points. The resulting equation was: 

 F = 0.86x + 4.5, where Y is standard length in mm and jc is the 

 distance from the nucleus to the anterior edge of the otolith in 

 arbitrary units, r 2 for this regression is 0.98. 



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