SHLOSSMAN and CHITTENDEN: REPRODUCTION OF SAND SEATROUT 



F— 



Figure 12. — Scale from a spring spawned 

 338 mm TL Cynoscion arenarius captured 

 in September showing two annuli (A). The 

 first annulus shows cutting over in the lat- 

 eral field and changed spacing of circuli as- 

 sociated with secondary radii in the an- 

 terior field. The second annulus shows cut- 

 ting over in the lateral field and a clear zone 

 between circuli in the anterior field. A false 

 annulus iFi had a few secondary radii but 

 lacked changed spacing between circuli or a 

 clear zone and distinct cutting over and was 

 absent on most scales. 



A- 



Ik^ 



f^ 



%%■ 



L 



Figure 13. — Scale from a late summer spawned 300 mm TL 

 Cynoscion are^arn/ .s captured in December showing one annulus 

 I A). Note the cutting over in the lateral field and secondary radii 

 in conjunction with a clear zone between circuli in the anterior 

 field, 



SO that their first annulus primarily formed from 

 April through July. Marginal increments in spring 



I'^ihiiiliii, 



fish were smallest in late summer and fall, so that 

 their first annulus formed primarily from Sep- 

 tember (possibly August) through November. 

 Therefore, both spring and late summer fish 

 primarily formed their first annulus at about 0.5- 

 0.75 yr of age. 



Fish with one annulus were 136-329 mm TL. 

 The percentage having a first annulus increased 

 with size: 1) 8% at 150-199 mm Thin = 518), 2) 24% 

 at 200-249 mm (n = 268), 3) 52% at 250-299 mm in 

 = 77), and 4) 71% at 300 mm and greater (n = 14). 

 Fish with two annuli were 265-338 mm TL. 



Back-calculated lengths were smaller than 

 lengths at age determined from length frequen- 

 cies. Lengths at annulus formation for spring fish 

 using Jones' (1958, equation 2) formula were 

 81-257 mm TL, and the mean was 162 mm with 

 95% confidence limits of 154-171 mm. Back- 

 calculated lengths at annulus formation for late 

 summer fish were 96-255 mm TL, and the mean 

 was 178 mm with 95% confidence limits of 169-186 

 mm. These data support analyses of marginal in- 

 crements that indicate the first annulus primarily 

 forms at 0.5-0.75 yr, because lengths at age I de- 

 termined from length frequencies were 220-280 

 mm TL for spring fish and 210-250 mm for late 

 summer fish. The back-calculated size range of 

 81-257 mm TL for spring fish agrees with their 

 sizes at age during summer and early fall (Fig- 

 ures 4, 5). Similarly, the back-calculated size 

 range of 96-255 mm TL for late summer fish agrees 



661 



