642 



Fishery Bulletin 100(3) 



Table 1 



Standard length (mm) at age for Prionotus carolinus and P. evolans from two different geographic regions. Fishes older than age 6 

 are not included because they were typically represented by only individual fishes, nd = no data. 



Age (yr) 







1 

 2 

 3 

 4 

 5 

 6 



^ Average lengtli values converted from fork length using equations in Wong (1968; Tables 2 and 3). 



-' Values are medians converted from fork lengths as reported in McEachran and Davis (1970, p. 347-348). 



' Values estimated as a median from Richards et al. (1979; Fig. 7i. 



plemental feed with vitamins and oils was given at least 

 once each week. Their ration was approximately 10% of 

 their body weight/day; this ration was adjusted 1-3 times 

 weekly to reflect the changes in weight during the experi- 

 ment. Uneaten food was removed daily. Three to seven fish 

 were removed from each replicate aquarium after 16, 26, 

 36, 46 days (total n=75), measured to the nearest 0.1 mm 

 SL, and preserved in 95% ETOH. Growth rates between 

 the replicate tanks varied from 0.21 to 0.44 mm/d accord- 

 ing to least squares, linear regression of standard length 

 on date of removal. Eleven of 86 fish initially placed in the 

 aquaria died during the experiment and were not used for 

 validating microincrement deposition rate. 



After preservation, both sagittae were extracted from 

 each fish, mounted on a coded glass slide in nail polish, 

 sanded along the sagittal plane, and swabbed with im- 

 mersion oil. After a fluorescing increment was located in 

 the ocular crosshairs using a ultraviolet light source, the 

 light was turned off and I counted the microincrements 

 from the crosshair to the otolith margin on three separate 

 dates. An average of these three counts was used to esti- 

 mate increment number from the tetracycline mark to the 

 peripheral edge. 



Daily age and growth 



Sagittal microincrements were examined from other 

 postsettlement P. carolinus and P. evolans juveniles col- 

 lected during August-October 1991 at locations in Great 

 Bay (New Jersey), Delaware Bay, and continental shelf 

 sites between Chesapeake Bay and Long Island Sound. 

 Fishes were collected with bottom trawls and seine nets 

 and either preserved in 95% ETOH or frozen. Specimens 

 for aging were subsampled in a stratified (1-mm length 

 category) random manner to proportionally represent the 

 complete size range of each independent sample. 



Otoliths were mounted on coded slides in nail polish 

 and sanded to the core along one side of the sagittal plane 



or embedded in an epoxy resin and sectioned to the core 

 (Secor et al., 1992). I counted microincrements through a 

 compound microscope, typically at 400x by using polar- 

 ized light, on three separate occasions. If the range of all 

 three counts was >20%' of the mean count, then the speci- 

 men was excluded from further analyses; this criterium 

 resulted in 14 of 137 specimens being rejected. The mean 

 increment count for sagittae was used to estimate "otolith 

 age" in days. Daily age included four additional days — an 

 estimate of the time between hatching and the date of 

 first ring deposition. Hatching dates were calculated by 

 subtracting daily age from date of capture. 



Annual age and growth 



Size attained by the end of the first growing season was 

 estimated from P. carolinus and P. evolans juveniles col- 

 lected during later winter and early spring cruises by 

 the National Oceanic and Atmospheric Administration's 

 National Marine Fisheries Service (see also McBride et 

 al., 1998). Fishes were sampled with bottom trawls during 

 two consecutive cruises (February 1993 and March-April 

 1993), which included a total of 447 stations (Fig. 1). The 

 effective period of sampling for searobins was actually 

 February-March (only one searobin was caught in 160 

 tows made during April). 



At sea, only fishes <120 mm SL were saved because 

 larger fishes were presumed to be older than 1 year (see 

 Richards et al., 1979). Fishes were kept frozen to preserve 

 the otolith structure. Specimens were subsampled from 

 each independent sample (i.e. tow) in a stratified (5-mm 

 length intervals), random manner This subsampling ap- 

 proach was chosen again to moderate the resulting sample 

 size while proportionally representing the complete size 

 range of each independent sample; this approach also 

 exaggerates the size range by dampening the modes of re- 

 sulting size-frequency data. Sagittae were mounted in nail 

 polish on a coded glass slide, sanded, and polished along 



