536 



Fishery Bulletin 90(3). 1992 



SL in their first growing season, with a modal size of 

 75 mm in October (Fig. 6). One-year-old fish reached 

 a size of 110-170 mm SL by the end of their second sum- 

 mer, with a modal size in September of 155 mm. 



Comparison of otolith ages (total increment counts) 

 with standard lengths provided a general estimate of 

 juvenile growth. The resulting relationship was best 

 described by a square-root equation (Fig. 7), indicating 

 a slight decline in absolute growth rate with age. If the 

 data are fit to a linear equation, a slope of 0.47 results, 

 thus estimating an average rate of 0.47 mm/day dur- 

 ing the early juvenile stage. Substantial variability was 

 evident, especially among older individuals (Fig. 7). 



To obtain an estimate of growth based on length- 

 frequency distributions, we compared length with the 

 date of capture for 236 juveniles collected only by throw 

 traps in 1988. When the mean length each week was 

 regressed on time (Julian date), the resulting slope pro- 

 vided an estimated growth rate of 0.52 mm/day (Fig. 8). 



Discussion 



Spawning patterns 



Based on the seasonal occurrence of eggs and larvae, 

 the peak spawming period for tautog in the Mid-Atlantic 

 Bight and inshore New Jersey waters is during the 

 summer. Spawning appears to follow a geographical 

 progression, beginning earlier in the southern part of 

 the region. Consistent with this pattern, Eklund and 

 Targett (1990) report that gonosomatic indices of adult 



D 



-o 



C 

 D 



JUL 10 JUL 30 AUG 19 SEP 8 SEP 28 



Date of collection 



Figure 8 



Mean and range in standard length of juvenile 

 Tautoga onitis collected on a weekly basis in 1988. 

 All fish were collected with throw traps, primarily 

 from artificial seagrass substrates. The regression line 

 was fit to means for each sampling date (n 13). 

 Numbers above ranges are the number of tautog col- 

 lected each week. 



tautog off Maryland and northern Virginia are highest 

 in May. 



The egg collections in New Jersey and high egg and 

 larval abundances in areas such as Narragansett Bay 

 (Bourne and Govoni 1988) demonstrate that tautog 

 spawn primarily inside estuaries or nearshore waters. 

 The MARMAP collections indicate that spawning 

 activity involves offshore continental shelf waters as 

 well, since all of the tautog larvae obtained during 

 MARMAP surveys were preflexion stage. 



Otolith deposition patterns 



Otolith increments of juvenile tautog can be reliably 

 used to obtain valuable age and growth information. 

 The strong correspondence of otolith size (based on 

 radial measurements) with fish size suggests that ac- 

 curate back-calculation of size-at-age is possible. In- 

 crements on the sagittae are deposited on a daily basis 

 and can be readily separated into planktonic and 

 demersal stages, due to the distinct contrast in micro- 

 structure at the time of settlement. We did not, how- 

 ever, test increment deposition rates under conditions 

 of poor or negative growth. These conditions have 

 resulted in less than daily increments in other species 

 (Geffen 1982, Lough et al. 1982, McGurk 1984, Alhos- 

 saini and Pitcher 1988, Siegfried and Weinstein 1989, 



