spawning beluga or stellate sturgeon, that later en-
tered the river.
The number of Russian sturgeon juveniles re-
leased from sturgeon hatcheries increased from 0.7
million in 1955 to 20–40 million in 1980–1983. How-
ever, these numbers also failed to stabilize the size
of the Russian sturgeon population in the Volga
River and Caspian Sea. Artificial reproduction of
Russian sturgeon has not compensated for stock
losses caused by overfishing, pollution and other
anthropogenic factors. As previously mentioned,
decreases in water levels in the Caspian Sea in the
1980s may also have negatively impacted both
growth and survival of juveniles in the Volga River
delta during their first winter, while fish are adapt-
ing to more saline conditions. To offset a continuing
decrease in the size of stock, 40 to 60 million juve-
nile Russian sturgeon were released annually from
1986 to 1990 (Figure 3). In the late 1980s, hatchery
propagated fish represented an estimated 25–30%
of the catch.Influenceofdamsonnaturalreproduction
construction of a series of hydroelectric dams in the
middle reaches of the Volga River in the 1950s
blocked sturgeons from reaching their primary
spawning sites. Only 372 from a total of 3390 ha of
suitable spawning area is left intact (Khoroshko
1970). The success of natural reproduction depends
on the volume of water during spring flood, runoff
during the summer, water temperatures during the
spawning, amount of suitable spawning grounds
available, the condition of the substrate of the
spawning grounds, the number offish reaching the
spawning grounds, and the quality or condition of
spawners reaching the spawning grounds. As a re-
sult of new fishery rules introduced in 1986 in the
Volga River Delta, the period of legal harvest in the
river was shortened to increase the number of
spawning fish reaching the spawning grounds. This,
and favorable ecological conditions (i.e., an in-
crease in water levels in the river and the Caspian
Sea), allowed natural reproduction to increase in
the late 1980s. However, levels of poaching in the
Caspian Sea and in the Volga River have increased
immensely in the last few years, which has de-
creased the efficiency of natural reproduction of all
three commercial sturgeon species.
Water pollution and illegalharvest asthreatsIn 1984, specimens of Russian sturgeon with degen-
erated muscles began to appear in the Volga River
and the Caspian Sea. In 1987, muscle degeneration
was noted on a massive scale in all three commercial
sturgeon species covered in this paper (Altufev et
al. 1989, Lukyanenko 1990). The phenomenon was
called ‘muscle atrophy’ and was intensively studied
from 1987 through 1992 (Evgeneva et al. 1990, Altu-
fev et al. 1992, Kuzmina et al. 1992). Results indicat-
ed that fibrils of the striated muscle tissues degener-
ated and were replaced by fat and connective tis-
sues. It was suggested that muscle atrophy was
caused by cumulative toxicosis resulting from in-
creasing pollution levels in the Caspian Sea basin
(Altufev et al. 1989, Lukyanenko 1989). Volga River
water pollution also was extremely high by the late
1970s. In 1979, the concentration of the pesticide
hexachlorane ranged between 0.0003 mg 1–1in the
Volga River delta and 0.0025 mg 1–1near the city of
Volgograd (Lukyanenko 1990). Water pollution has
increased since then. Recent experiments support
the hypothesis of pollution-caused etiology of mus-ArtificialpropagationThe Volga River sturgeon hatcheries are situated
next to the river and began to release juveniles into
the Volga River first in 1957; trends since then are
shown in Figure 3. Juveniles are released into the
river at age of 30–50 days (Lukyanenko et al. 1984).
The number of beluga juveniles increased from 0.5
million in 1959 to 16.0 million in 1970. However, we
found that this did not increase the number of belu-
ga harvested in later years. The release of stellate
sturgeon juveniles, along with a ban on sturgeon
catch from the sea in 1962, resulted in increases in
the number of stellate sturgeon caught. In the late
1980s, 30% of the stellate sturgeon harvest was
from hatchery produced fish. Unfortunately, in-
creases in the number of juveniles released from
hatcheries did not seem to affect the number of