FISHERY BULLETIN: VOL. 71, NO. 4 



(column A, Figure 3) were 2-yr-olds prior to 

 formation of the second annulus. The greatest 

 percentage of fish with the second annulus at 

 the centrum edge occurred in September. An- 

 nulus formation on the centrum may take long- 

 er than on scales and otoliths because vertebrae 

 are larger and structurally more complex. 



958 



Figure 2. (left) — Vertebral sections of the northern 

 puffer showing the increase in margin width after forma- 

 tion of the first annulus: (a) young-of-the-year female cap- 

 tured in November, (b) female captured in May with the 

 first annulus just visible at the centrum edge, (c) age I male 

 captured in September, (d) age I male captured in 

 November. 



20-1 



lO 



A 



30 



20H 



ID 







-r-r-T+ 



April 

 N = 50 



■4+x- 



May 

 N = 93 



J^ 



,jPIppii 



-p-p- 



30- 

 20- 



10- 

 0- 



20 



I OH 







April 

 N = 24 



U- 



May 

 N = 25 



X 



30- 

 20- 



10- 

 0- 



June 

 N = 5I 



l|' IM J ' H 1 tl P ? , , P , . 



IxJ 



< 



o 



a: 



UJ 



Q- 



20- 



10- 

 0- 



^m- 



40-1 

 30 



20- 

 10 

 



40- 

 August 30- 



N=52 20H 



10 



July 

 N = I6 



WU^ 



I I I 1 I I I I 



Sept.-Oct. 

 N = II5 







August 

 N=29 



1 ^ 1 I I  t1 



20 



lo-H 

 o 



-4#^ 



H^ 



50 

 40- 

 30 

 20 



10- 

 



Sept.-Oct. 

 N=39 



WW- 



30- 

 20- 

 10- 



0- 



Nov. 

 N = 25 



T — r — p-T — t — I V 'I' I 'r 

 5 10 



^ 



MARGINAL WIDTH (ocular micrometer units) 



Figure 3. — Frequency distributions of margin width; 

 (distance between the last annulus and the centrum edge 

 of vertebral centra from the northern puffer: (A) with 

 a single annulus, (B) with two annuli. 



Yasuda (1940) showed that annuli on vertebrae 

 of Scombrops sp. were formed 1.5 mo late: 

 than on otoliths. In older fish the length of timi 

 for annulus formation may be extended furthe: 

 because of the decreasing annual addition t< 



h 



h 



