Sogard et al Early life history of Tautogs onitis in the Mid- Atlantic Bight 



533 



between left and right (paired comparisons (-test: 

 P>0.10), with the two sides differing by <2%. Thus, 

 either sagitta could be used for increment counts. 



The mean duration of the planktonic stage was 

 estimated by the mean number of increments preceding 

 the settlement mark. Birth and settlement dates were 

 estimated by subtracting the number of total incre- 

 ments and juvenile increments, respectively, from the 

 date of capture. Assuming that initial increment for- 

 mation occurred at about the time of hatching, as in 

 other wrasses (Victor 1982), our estimates of birthdates 

 should correspond within a few days to the date of 

 hatching. 



Juvenile growth rates 



We used three independent methods to estimate 

 growth rates of young-of-the-year juveniles during the 

 summer. The relationship between otolith age (total in- 

 crements) and standard length was fit to a linear equa- 

 tion, using the slope as an estimate of daily growth. 

 We also examined the progression of mean lengths for 

 tautog collected on a weekly basis in 1988 (primarily 

 from artificial seagrass experiments). Weekly mean 

 lengths were determined and regressed on time, with 

 the slope of the resulting equation used as a second 

 estimate of daily growth. Growth rates based on these 

 two indirect estimates were compared with a third, 

 direct measurement of individual tautog growth in field 

 caging experiments by Sogard (In press). 



Results 



Reproductive seasonality 

 and larval distribution 



In the Great Bay-Mullica River 

 estuarine system, tautog eggs oc- 

 curred in plankton collections 

 from April through August, with 

 peak abundances in June and 

 July (Table 2). Initial occurrence 

 and peak abundance of eggs 

 were earlier in the Mullica River 

 than in the bay and adjacent in- 

 let, suggesting that spawning 

 began earlier in the season in the 

 upper part of the estuary, and 

 continued later in the summer in 

 the lower estuary and offshore 

 waters. Tautog larvae in weekly 

 plankton collections in Great Bay 

 (Table 1) occurred in July and 

 August of 1989 (n 12) and July of 

 1990 (w 9). Larvae were collected 



in the offshore MARMAP surveys from May through 

 October, with a peak in July (Table 3, Fig. 2). 



Based on geographic distribution of larvae, spawn- 

 ing was concentrated in southern New England waters 

 (Fig. 2). Spawning activity in continental shelf waters 

 appeared to follow a northward progression through 

 the summer, beginning as early as May in the southern 

 part of the region (Table 3). 



Daily increment validation 



Results of the validc.tion tests indicated that increments 

 on sagittae of juvenile tautog were deposited on a daily 

 basis. The slope of the regression comparing the actual 

 number of days elapsed with the number of increments 

 following tetracycline marks did not differ from 1 

 (P>0.05, r2 0.86, Fig. 4). Comparison of sagittal 



