348 



Fishery Bulletin 101(2) 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 



Month 



Figure 4 



Catch per unit of effort for juvenile striped mullet in South Carolina estuaries from 

 rotenone surveys, 1986 to 1991. n = 4246. 



regimes showed that most of these fish were recruiting 

 into mesohaline and polyhahne sahnities. One difference 

 in the rotenone data was that few juveniles were caught 

 at ohgohahne sites during the recruitment time period. 

 Young-of-the-year striped mullet were caught at euhaline 

 sites starting in May when the mean size was greater than 

 40 mm. Specimens captured by plankton net in freshwater 

 and oligohaline salinities had very low abundances. The 

 plankton net did not catch any juveniles in euhaline sa- 

 linities. Catch per unit of effort (CPUE) for the rotenone 

 surveys also demonstrated increasing abundance from 

 February to May (Fig. 4). 



Size frequencies in the different salinity regimes for the ju- 

 venile aging study ( Fig. 5) showed young-of-the-year striped 

 mullet (fish less than 200 mm) were found mostly at meso- 

 haline and polyhaline salinities. The earliest occurrence of a 

 young-of-the-year specimen in the juvenile aging study was 

 a 25-mm specimen captured in December of 2000. 



Age validation 



The variability in the physical parameters during the age 

 validation experiment approximated the diurnal varia- 

 tions in tidal creek habitats. Temperature and salinity 

 ranged from 14.2° to 19.0°C and 21.3 ppt to 29.0 ppt . Dis- 

 solved oxygen ranged from 6.2 mg/L to 8.1 mg/L during 

 the experiment. 



There was no detectable growth during the experiment — 

 probably a result of the short duration of the experiment. 

 Age ranged from 57 to 121 days and moan age was 83 ±17.4 

 days. The mean ago did ineroaso over tho course of the ex- 

 periment with each collection (65.3 ±1.45 days, 82.2 ±2.47 

 days, and 102.5 ±3.59 days, respectively). 



The OTC mark was visible under UV fluorescence on 

 all the specimens examined. A paired /-test between the 

 number of days after OTC marking and the number of 

 increments counted after the OTC mark showed that the 

 two variables were not significantly different (P=0.000, 

 /=0.000, df=29, F=1648.0). Regression analysis (Fig. 6) 

 indicated that the slope of the line running through these 

 points did not differ significantly from 1.0 (r2=0.998). These 

 analyses allow the acceptance of the null hypothesis that 

 the increments counted were deposited daily. 



There was an 84.5% agreement between the original age 

 and the second age read for the subsample of 69 specimens 

 that were re-aged. An age bias plot (Fig. 7) showed the 

 difference between the two ages for each specimen and 

 the original age assigned to that specimen showed no de- 

 tectable age bias. In addition, the coefficients of variance 

 for each set of ages were similar (originally assigned age 

 CV=0.434 and the second blind read age CV=0.429). An 

 ANOVA comparing the mean ages for each group (original 

 age=170.7 ±8.93 and blind read second age mean=170.6 

 ±8.80) also showed no significant differences (P=0.00, 

 df=68,F=6878.8). 



Growth 



Growth of striped mullet from the juvenile aging study was 

 described by the equation 



Total length = 0.342 (Age)> "39 ±19.4 



(r2=0.741 atP=0.001). 



Size at ago was more variable in fish larger than 90 mm TL 

 (Fig. 8); however, there was still clearly a strong relationship. 



