50 



Fishery Bulletin 91(1), 1993 



2.3 



2.5 2.6 2.7 



Log TOTAL LENGTH (mm) 



2.8 



2.9 



Figure 6 



Length-weight relationship for male Tautoga onitis collected 

 in coastal waters of Virginia, 1979-86. 



weights (Tables 2,3) increased with age for both sexes 

 (P<0.01). 



Estimates of mean back-calculated size-at-age (Tables 

 4,5) suggest that growth for male and female fish is 

 similar. However, we analyzed the data by sex to com- 

 pare with previously reported values. Greatest incre- 

 mental growth in TL for both sexes occurred during 

 the first year and then declined rapidly. Growth in the 

 second year was only 40-49% of that recorded for the 

 first year for both sexes (Tables 4,5). Only small differ- 

 ences in back-calculated lengths-at-age occurred be- 

 tween the sexes to age-13 (Tables 4,5), and these were 

 not statistically significant. Males usually had a slightly 



larger growth increment at each successive age 

 throughout the life span. 



Estimates of empirical length-at-age (Table 6) com- 

 pared favorably with both back-calculated estimates 

 (Tables 4,5) and observed growth (Tables 2,3). K-va\ue 

 for male tautog (0.090) was greater (Table 6) than that 

 calculated for females (#=0.085). Males were also larger 

 in size (TL) when compared with females of compa- 

 rable age (Fig. 8), although the differences were not 

 statistically significant. Males and females achieved 

 50% of L„ between ages 6 and 7, and 75% between 

 ages 14 and 15. ANCOVA analyses indicated no sig- 

 nificant differences between slopes of regression equa- 

 tions of length-at-age for male and female tautog 

 (/ r =2.600, P>0.05) or for homogeneity of means around 

 regression slopes (F=2.979, P>0.05). 



Derived length-at-age estimates from von Bertalanffy 

 growth equations were later used in regression equa- 

 tions to calculate weight-at-age. Although correlation 

 coefficients were high (r=0.81) in the analysis of WT 

 on TL, variation in weight-at-age within age-groups 

 was considerable, and estimates of growth based on 

 weight were less reliable than estimates based on TL. 



Sexual dimorphism and reproductive biology 



We observed two different morphological males in fish 

 we examined. Approximately 15% of the fish we classi- 

 fied initially as females, based on external characteris- 

 tics, were later determined upon dissection to be males. 

 Generally, these non-dimorphic males were fish smaller 

 than 550mmTL and less than age-10. However, sev- 

 eral approached the largest sizes observed for other 

 males. Pigmentation of non-dimorphic males was a dull 

 mottled brown, with remnants of disrupted lateral 

 bands, and was similar to that noted for females. In 

 contrast, dimorphic males were typically grayish with 

 distinctive white markings on ventral and dorsal mar- 

 gins of pectoral and caudal fins and on the chin. The 

 anterior skull and rostral region were also blunter and 

 more massive in dimorphic males than for those noted 

 in females and non-dimorphic males. Both types of 

 morphological males were considered as males in analy- 

 ses of age and growth and sex ratios. 



Gonadal maturation was evident in both sexes by 

 age-3. Age-2 fish, collected only in late March and early 

 April, were immature with undeveloped gonads. GSI 

 values for females plotted against date of capture (Fig. 

 9) indicated peak spawning from April through June, 

 with the highest GSI recorded in May. GSI values de- 

 clined rapidly after July. Although not shown, the GSI 

 of tautog collected inside and at the mouth of Chesa- 

 peake Bay peaked somewhat earlier, in mid-May, and 

 started to decrease by mid-June, whereas a small per- 

 centage (usually -20%) of running ripe fish were 



