802 



Fishery Bulletin 90(4). 1992 



Sample; SC-1 



LM^U 



" " Mean Ratio 



Sample: SC-2 



CO 



lii 4 

 >< 



i 3 



o 



9 1 

 in 



\±± 



1 li i "" 



- - Mean Ratio 



12 3 4 5 6 



age 



Figure 3 



Transects of Sr/Ca ratios across annuli of adult female Santee- 

 Cooper (SC) striped bass Morone saxatilis. Mean ratios are 

 plotted across all ages. 



24 



20 - 



O 



0. 



Q 16 



LU 

 _l 

 Q. 



s 

 < 



CO 12 



u_ 



O 



> 



o 



g 8 



O 



m 



J Sample MD-1 , Trial 2 (Step=20/jm) 



> 



Strontium was not detected in the Patuxent River 

 juvenile striped bass otolith until it reached ~8mmSL 

 (Fig. 5). Because larvae less than this size tend to utilize 

 freshwater nurseries (Houde and Rutherford 1992), 

 this further verified that freshwater residence results 

 in low levels of otolith Sr. 



Discussion 



Annulus formation 



Rate and season of annulus formation in striped bass 

 otoliths are critical to interpretation of the results on 

 annual and seasonal changes in otolith microchemistry. 

 Heidinger and Clodfelter (1987) validated the hypoth- 

 esis of yearly annulus formation for young (<5 years 

 old) striped bass. However, no directed research has 

 documented the time of annulus formation in striped 

 bass otoliths or scales despite their widespread use in 

 fisheries (e.g., Beamish and McFarlane 1983). Several 

 investigators have made the observation that annuli are 

 not observed until spawning season in scales (Merriman 

 1941, Robinson 1960) and otoliths (M. White, S.C. 

 Wildl. Mar. Resour., Bonneau SC 29431, pers. com- 

 mun.). Based on these limited observations and the 

 general trend of spring annulus formation in other 

 North American temperate fishes, it was assumed that 

 annular check formation occurred during or just prior 

 to the spawning season (February-April). 



Salinity effect on otolith 

 microchemistry 



Sample MD-1, Trial 3 (Step=13/jnn) 



SOum Contour. Slep=13(jn<- — ^------a. 



StV^rn Contour, Step=2Qunv 



2 3 4 5 6 7 



Figure 4 



Number of sampled points between annuli checks at two step sizes. Contours for a 

 hypothetical SOpim annular increment are plotted at 13 and 20jim step sizes. 



Because Chesapeake samples 

 had substantially higher Sr/Ca 

 ratios than South Carolina sam- 

 ples, there appears to be a salin- 

 ity effect on the ratio. This con- 

 clusion is further substantiated 

 by the juvenile otolith that was 

 examined and showed nondetect- 

 able Sr/Ca ratio during the early- 

 larval period, a time when Chesa- 

 peake tributary larvae generally 

 occur above the salt-wedge 

 (Uphoff 1989, Houde and Ruth- 

 erford 1992). Patterns in otolith 

 Sr/Ca in adults were consistent 

 with expected seasonal changes 

 in ambient salinity. The range of 

 ratios found for Chesapeake 

 striped bass was similar to those 

 found by Kalish (1989) for 12 

 marine species (Sr/Ca 0.0018 



