Fisheries.–The pull nets and rowhooksused to cap-
ture sturgeons in the Amur River until the 1950s
were replaced by three-layer gill nets. Fishing im-
pact on sturgeons was low before the 1970s because
few people lived along the Amur River. However,
with increasing population and the high profit of
sturgeon fishing, catches increased. There are now
2 to5 sturgeon fishing boats per kilometer along the
mid reaches of the Chinese side of the Amur River,
and annual exportsofcaviarincreasedfrom 3 met-
ric tons in the 1970s to12 tons in 1990. Separate catch
data for the two species are not available. Incom-
plete statistics from 9 sites show that the annual
catch from 1952 to 1956 and 1959 was commonly 70
to 80 tonsyear-1in the entire middle reaches of the
Chinese side, with a minimum of 30 tonsyear-1.In
1978, 90 tons were harvested, 141 tons in 1981,175
tons in1985, and 200tons by1987. Inrecentyears,
production decreased at somelocations,especially
in the uppermiddle reaches, despite comparable
fishingeffort. Fishing has moved to the lower part
of the mid reaches, andharvests in theseareas are
now declining.Annualcatches at Qingdeli, for in-
stance,were 36.3,31.7,27, 26.7 and 21.6tons in the
years from 1985 through 1989.
Most of thefishtaken arespawning-sizedadults.
This has grave consequences for thefuture of the
fishery. We sampled 256 Amur sturgeonfrom fish-
ermen at Luobei, whichincluded 123 young fish
rangingfrom 20 to 100 cm TL, and 133adults rang-
ing from 100 to 180 cm TL. In anotherlarge sample
of Amur sturgeon (407 individuals fromZhaoxing
and Qingdeli), young fishaccounted foronly5.7%
of the total sample. ForkalugafromZhaoxing and
Qingdeli, youngaccounted for 29.3% of the total
sample.Conservation efforts. –The government of Heilong-
jiang Provinceissued specificregulations for the
protection and management of sturgeons in the
1950s, and renewed them in 1982. Current regula-
tions are not fully implemented because of insuffi-
cient management. Furthermore, some regulations
are based oninsufficient understanding of the
stocks. As thestocks declined, a propagation sta-
tion for Amur sturgeon was set up at Qingdeli in- About 900 000 larvae (0.2 to 0.4gBW) and
counted for 87.4% near Zhaoxing, whereas fish be-
tween 180 and 300 cm TL accounted for87.4%near
Qingdeli(Table 3). Body weight ranged from 40-
501kg. In a sample of 79specimens, 74.7% were be-
tween 40 and 165 kg BW. Females tended to be
largerthanmales. In a sample of 53 females, 52.8%
ranged from 90 kg to 190kg, and41.5%ranged from
190 kg to501 kg. The spawning population ranged
from 12 to 54 years of age (Table 4). Age is positively
correlataed with length and weight. The oldest indi-
vidual (54years) was also the largest at 390 cm T L
and 501 kgBW.Sex ratios differed between the up-
per and lower middle reaches. The ratio of malesto
femaleswas1.4: 1 nearZhaoxing(N =113) and 3.7: 1
near Qingdeli (N=48). The average GSI for fe-
males was 13.9% in May (maximum of 17.3%); by
June, the GSI was 14.1%(maximum of 18.4%). Fe-
cundity ranged froma 383 400 to 3 280 000 (N=22;
224–390 cm TL). Meanfecundity was 600000,
1500 000,and 3000 000for individuals withTL
224–274 cm,281–327 cm and350–390 cm,respec-
tively. Thenumber ofeggs per gram ofbodyweight
ranged from 27.8 to 53.0,with a mean of41.4.Ripe
eggs rangedfrom 2.5 to 3.5 mm.
Reproduction.–Both Amur sturgeon andkaluga
usuallyspawn between May and Julywhen water
temperatures range from 15° to 20°C. Spawning
habitat ischaracterized by calm water and sand and
gravel substrates. Kaluga spawn at a depth of 2 to 3
m. Appropriatespawning habitat isavailable from
the upper to thelower middle reaches of the Amur
River. Known spawning sites are located at the
mouth of thePingyanghe and Xueshuiwen rivers in
XunkeCounty, in the Yadanhe and Zhaoxing rivers
within LuobeiCounty, and in theQingdeli and Xia-
baca rivers within Tongjiang County. Wehave not
found anyspawning sites in the Songhuajiang and
Wusulijiang rivers.
Natural hybridization occurs betweenkaluga and
Amur sturgeon in the Amur and Songhuajiang riv-
ers (Ren 1981).Historically, the hybridswere con-
sidered a distinctspecies(Gong 1940). Theyhave
intermediate characteristics and resembleartificial-
ly produced hybrids (Krykhtin&Svirskii1986, fig.
2d).