Figure3.Total number of occurrences of adult Chinese paddlef-Figure2.Size frequencydistribution of Seventeenadult Chinese ish,Psephurusgladius,belowGezhouba Damfrom 1981 to 1993
paddlefish.Psephurus gladius,found below Gezhouba Dam be-
tween 1982 and 1986.
been unable to hold brood fish for more than a
month.
Chinese sturgeon, Acipenser sinensis
As presently understood, the Chinese sturgeon is
restricted to the main channel of the Yangtze River,
the Pearl River, and the East and South China Seas
(Figure 1). There is still uncertainty about the taxo-
nomy of the two populations in the Pearl and
Yangtze rivers. The original specimen ofA. sinensis
(32 cm TL), collected by Reeves, may have been
from the Pearl River (Anonymous 1988). Wu et al.
(1963) considered the larger anadromous sturgeon
from the Yangtze River to beA.sinensis[note that
Zhu (1963), regarded all sturgeon in the Yangtze
River and in the East China Sea to beA. dabrynnus,
an opinion not shared by later workers]. It has been
suggested that the large anadromous sturgeons of
the Pearl and Yangtze rivers should be considered
as two isolated species (Anonymous 1988). The
large anadromous sturgeon from the Pearl River
seem to differ in morphology, spawning time and
migration pattern from those in the Yangtze River
(Zhou et al. 1994), but much more evidence needs
to be collected to examine this taxonomic problem,
particularly because very little information is avail-
able about the Pearl River population (Zhen 1989).
The Pearl River population appears to be even
more endangered than the one in the Yangtze Riv-
er. A new hydroelectric project, the Changzhou
Dam, will block spawning migrations (Chu et al.
1994).
Migrationofthe Yangtze River population. -Adults
with gonads approaching maturity (in early stageIII), arrive from the sea in June or July at the mouth
of the Yangtze River to ascend its main channel
(Anonymous 1988). The adults do not feed while in
the river. They arrive at the Jingjiang reach, not far
below the Gezhouba Dam, in September or Octo-
ber, where they overwinter. Ripe individuals were
formerly found as far inland as the Jingsha River
(Figure 1) during the following October and No-
vember, where they spawned. Prior to construction
of the Gezhouba Dam, the migration distance was
as long as 2500 to 3300 km.
JuvenileA. sinensis7 to 38 cm TL occur in the
Yangtze River estuary from the middle of April
through early October. These are presumably one
year old individuals (Wei et al. 1994, Anonymous
1988). Juveniles weighing a few kilograms can be
found in coastal waters near the river mouth. Indi-
viduals from 25 to 250 kg in weight were registered
in some fishing grounds of East China Sea and Yel-
low Sea (Anonymous 1988).Structure of the Yangtze River population.–Some
investigations on the structure of the spawning pop-
ulation have been performed (Ke & Wei 1992, Deng
et al. 1991. Anonymous 1988, Deng et al. 1985). Fe-
males are larger than males (Figure 4) and the sex
ratio is consistently about 1:1. We recorded the total
lengths (TL) of 475 individuals taken between 1981
and 1993, and found it to range from 189 cm to 389
cm (mean=273 cm). The 266 males in the sample
ranged from 189 to 305 cm TL (mean=242 cm), and
the 209 females ranged from 253 to 389 cm TL
(mean=313 cm). Fish weighed 42.5 to 420 kg (mean
of 213.7 kg). Males weighed 42.5 to 167.5 kg (mean
of 85.4 kg), and females weighed 104.5 to 420 kg
(mean of 217.3 kg). Total length is significantly cor-