Figure 4. Size frequency distribution of spawning population of Chinese sturgeon. A.
coded separately to show sexual dimorphism of this population. N = 475.
related with weight: BW = 1.1969 × 10–6T3.298 (N =
269,r = 0.9452, SBW.TL= 25.58. F = 2239.39).
From 1981 through 1993, 384 fish were used for
age determination. This sample included 214 males,
169 females and 1 inter-sexual. Fish ranged from age
8 to 34 years (N = 383). The mean age of the spawn-
ing population was 17.0 years (14.0 years Tor males
and 20.7 years for females, Figure 5). Males ranged
between 8 and 27 years, with the majority between
10 and 18 years (90.2%); females ranged between 13
and 34 years with the majority between 16 and 27
years (86.4%). Deng et al. (1991) reported that fish
making an initial spawning accounted for 84% of allsinensis, from 1981 to 1993. Males and females aremales and 76% of all females Our results differ. We
determined whether reproductive marks occurred
in all three structures used for aging (the first pecto-
ral fin ray, the clavicle and cleithrum) in a subsam-
ple of 341 of the 384 specimens. Reproductive
marks were indistinct in the remaining 43 speci-
mens, in which the average ages were 14.3 years for
males (N =18)and 21.4 years for females (N = 25).
The first column of Table 5 shows that individuals
making an initial spawning run accounted for
66.3% of males and 44.4% of females. We found
that the first spawning mark exactly recorded the
age of first reproductive migrations, allowing us toFigure 5. Age frequency distribution of spawning population of Chinese sturgeon. A. sinensis. from 1981 to 1993. N = 383.