354 



Fishery Bulletin 101(2) 



140 



120 



E 100 

 E, 



^ 80 H 

 a 



40 - 



Oligohaline 

 Mesohaline 

 Pulyhaline 

 Eiuhaline 



Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

 lytonth 



Figure 12 



Mean size per month for young-of-the-year striped mullet stratified by salinity 

 regime for pooled data from 1986 to 2000. n = 8714. 



to validate daily growth increments. Another more recent 

 study by Chang et al. (2000), using wild-caught striped 

 mullet marked with OTC, also validated daily growth 

 increments in Taiwanese estuaries. 



The variation in physical parameters of temperature, 

 salinity, and dissolved oxygen throughout the validation 

 experiment approximated the existing conditions found in 

 the harbor during this time period. Food sources may have 

 differed between the tank and the tidal creeks; however, 

 the fish were observed feeding on the growth on the sides 

 of the tank in addition to ingesting the floating commercial 

 food during most of the experiment. Because the mullet 

 were observed actively feeding during this experiment, 

 starvation stress probably did not affect increment depo- 

 sition. In addition, concurrent collections of wild striped 

 mullet for the juvenile aging study revealed size and age 

 distributions similar to those for specimens used in the age 

 validation part of our experiment. 



Validation of daily growth increments is an important 

 step in providing estimates of growth and age for larval 

 and juvenile fishes. Accurate age and growth information 

 enables better examinations of recruitment, population 

 dynamics, and other important aspects of the life histories 

 of juvenile fishes. Validation of daily growth increments in 

 striped mullet allows for more accurate estimates of age in 

 adults and juveniles, in particular, and thus this process 

 helps to determine the first growth increment. Validation 

 also helps determine different aspects of size at age in ju- 

 venile striped mullet, sexual differentiation, and develop- 

 ment, and a more precise determination of spawning time 

 periods in adult striped mullet through hack calculation 

 of birlhdates. 



Growth 



Growth of newly recruited fish during the January-April 

 time period was relatively low when compared to the rest 

 of the year. This time period also coincided with the time 

 of heaviest recruitment of these juvenile mullet. How- 

 ever, when we look at mean size per month for all of the 

 juveniles pooled together, we find a similar growth curve 

 in both the historical and current data. It was not until 

 May, when the juvenile striped mullet reach a mean size 

 of greater than 40 mm, that growth increased markedly. 

 The results of the growth curves from our study appeared 

 to support this. The greatest increase in growth came 

 after a mean size of 40 mm was reached and during the 

 months when mean monthly temperatures were higher 

 However, the differences in growth between different 

 salinity regimes examined in our study were not found 

 to be significant. 



Growth for juvenile striped mullet was similar in both 

 the rotenone study (1986 to 1991) and the juvenile aging 

 study (1998 to 2000). This was evident from the nonsig- 

 nificant differences in the slopes of the two curvilinear 

 regressions. The coefficient of variation was also similar 

 between the two groups. Because the growth rate for the 

 rotenone study specimens was calculated from pooled data 

 over a six-year period, it provided a fairly good estimate of 

 growth over a range of environmental and biological condi- 

 tions. As with the fish from the juvenile aging study, growth 

 in the rotenone mullet study was fairly flat from January 

 until May when mean size reached 40 mm or larger After 

 May the growth rate increased dramatically until it slowed 

 again in the fall. The increase in growth rate from May to 



