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Fishery Bulletin 90(3). 1992 



during the Rutgers Marine Field 

 Station trawl survey. A 4.9m ot- 

 ter trawl (6.3 mm mesh cod end, 

 19 mm mesh wings) was towed 

 for 2 minutes at a total of 14 sta- 

 tions, which were representative 

 of a variety of habitat types. 

 Four replicate trawls were taken 

 at each station. 



\ 



Otolith increment analysis 



More detailed information on 

 planktonic stage duration, settle- 

 ment patterns, and growth of 

 young-of-the-year tautog was 

 derived from analysis of otolith 

 increments. To validate a daily 

 rate of increment formation, the 

 number of increments following 

 a tetracycline-induced fluores- 

 cent mark on the sagitta was 

 compared with the actual num- 

 ber of days elapsed. Juvenile 

 tautog (19-63 mm SL) were im- 

 mersed for 24 h in a 500mg/L 

 solution of oxytetracycline dihyd- 

 rate in natural seawater (20-25 

 ppt) diluted with distilled water 

 to about 17 ppt. They were then 

 held in laboratory aquaria, fed 

 daily with Artemia, and pre- 

 served in 95% ethanol after 6-30 

 days. The sagittae of these indi- 

 viduals were removed, embedded 

 in Spurr resin, and polished in 

 the sagittal plane to the central 

 primordium on both sides, using 

 a series of 400-1500 grit sand- 

 paper and alumina powder (0.3 

 fim), following the methods of 

 Secor et al. (1991). The number 

 of increments following the tetracycline mark was 

 counted with UV microscopy at 400-1000 x magnifi- 

 cation. 



The degree of correspondence between otolith size 

 and fish size was determined for 55 juvenile tautog by 

 comparing radial measurements of the rostrum, post- 

 rostrum, and antirostrum (Fig. 3) with standard 

 lengths. Radial measurements were made with an 

 image analysis system attached to an Olympus BH-2 

 microscope, using a magnification on the monitor of 

 160 X or 410 X, depending on the size of the otolith. 

 The relationship between otolith radial measurements 

 and length (SL) of the fish was determined by regres- 



PR 



AR 



/ 



\ 



Figure 3 



Ground and polished left sagitta of a 38.7 mm SL juvenile Tautoga onitis. (upper) Photo- 

 graphed at lOOx magnification; scale bar = 200fim. R = rostrum. PR = postrostrum. 

 AR = antirostrum. Tip of the rostrum was partially destroyed during polishing, (lower) 

 Closeup view of central region (400 x ). Arrow points to transition between pelagic and 

 demersal stage increments. Scale bar = 50/jm. 



sion analysis. Because preliminary analysis of a 

 matched set of sagittae foimd no significant differences 

 between left and right radius measurements (paired 

 comparisons ^tests: n 8, P>0.10 for all three radii), 

 either sagitta was used in subsequent analyses. 



Increments were counted for a series of tautog (n 37, 

 7.6-62.8 mm SL) collected from early- July through late- 

 September in 1988. Larval and juvenile increments 

 were distinguished on the basis of an apparent settle- 

 ment mark in the sagittae (see below). Increments were 

 counted independently on three different dates by the 

 same reader, and the results were averaged. Prelim- 

 inary counts of matched sagittae found no difference 



