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Fishery Bulletin 94(4), 1 996 



estimated volumetrically by using three 5-mL vol- 

 ume subsamples. Egg diameters were measured 

 (±0.01 mm) along the animal-vegetal axis with a dis- 

 secting microscope and ocular micrometer. 



Procedures described in Steel and Torrie (1986) 

 were followed for statistical analyses. The Statisti- 

 cal Analyses System software (SAS, 1985) was used 

 for data processing. The measure of variability is 

 reported as standard error of the mean (±SEM), and 

 the accepted level of statistical significance is P<0.05. 

 All length measurements are given in fork length (FL). 



Results 



Body size, sex ratio, and sexual dimorphism 



We sampled a total of 855 white sturgeon, ranging 

 in fork length from 79 to 202 cm (mean=139 ±1.1 

 cm). Mean length of females (145 ±1.2 cm) was sig- 

 nificantly greater than that of males (133 ±1.0 cm). 

 The sex ratio was 1:1 (Table 1). The proportion of 

 males, however, was significantly higher among fish 

 <115 cm, whereas the proportion of females was 

 higher among fish >155 cm (Table 1). 



In most cases we could not determine by external 

 examination the sex of white sturgeon, except for 

 spermiating males and some ripe females (recognized 

 by an enlarged abdomen). We found no significant 

 differences between the sexes in numbers of dorsal 

 and lateral scutes, relative lengths of the head and 

 snout, and width of the mouth. Among all fish exam- 



ined histologically, we found only one case of her- 

 maphroditism, a maturing testis containing a few 

 ovarian follicles with previtellogenic oocytes. 



Distribution of maturity stages in the 

 population 



The smallest ripe female and male were 104 cm and 

 100 cm, respectively. The female sample population 

 comprised 70% group-1, 12% group-2, and 18% group- 

 3 individuals (Table 2). Except for one large size class 

 ( 175.1-185 cm), the proportion of immature females 

 remained high (>62%) in each length class. Although 

 females with vitellogenic or ripe ovaries (groups 2 

 and 3) appeared in length classes 95.1 to 125.1 cm, 

 their proportions were small (average 3% for group 

 2 and 6% for group 3). In 135.1-195 cm sturgeon, 

 the proportions of females with maturing and ripe 



