51813_Sturgeon biodioversity an.PDF

number of stellate sturgeon harvested varies from

194 000 in 1967 to 884 000 in 1986. From 85 000 to

388 000 individuals (20–44% of the total number of

spawning stellate sturgeons migrating into the Vol-

ga River) reached the spawning grounds below the

Volgograd Dam. Many stellate sturgeon reached

spawning grounds in 1978,1979,1983, and 1985–1988

(616 000–884 000 individuals. Figure 4). Harvests

varied from 3870 metric tons in 1960 to 4550 metric

tons in 1986.

The spawning stock of stellate sturgeon migrat-

ing into the Volga River in the late 1980s consisted

of fish either spawned after regulation of the Volga

River flow or from fish released from hatcheries. At

present, the generations hatched between 1972 and

1978 dominate the catch. The largest stock reported

consisted of 15.7% first-time-spawners, 72.9% sec-

ond-time-spawners, and 11.4% older individuals

(Table 1). Anincrease in the number of spawning

stellate sturgeon migrating into the Volga River in

the late 1980s could be due to stabilization of nat-

ural reproduction in this species.

From the late 1960s until 1985, fewer stellate stur-

geon have entered the Volga River (approximately

500 000 on average) than the Ural River (800 000-

1300 000, Figure 4).The number of stellate stur-

geon decreased in the Ural River because of over-

Stellate sturgeon fishing and insufficient annual recruitment, and be-

tween 1986 and 1992, stocks have declined sharply

Stellate sturgeon still have natural spawning in both rivers. In 1992, the Ural River population

grounds below the Volgograd Dam, and 60% of was only one-third of the number observed in 1986.

their historic spawning sites remain intact. The

Table 1.Changes in the percent composition of spawning populations of sturgeons in the Volga River during the last 35 years.

Species and characteristics 1965 1980 1985 1991

Beluga sturgeon

However, since 1979, the number of beluga entering
the Ural River has exceeded the number entering
the Volga River. The ban on sturgeon harvest from
the Caspian Sea enacted in the 1960s contributed
greatly to the increase in the number of spawning
beluga that migrate into the Ural River.
The biomass of beluga from the 1952 through
1976 generations, which took part in spawning dur-
ing the years 1978 through 1987, grew from2800 to
4000 metric tons. In 1990, about 14000 individuals
migrated into the Volga River from the sea. Ap-
proximately 35% were females and males which
were spawning for the first time (11–17 years old),
60% of the fish were spawning for the second time
(18–30 years old), and the remaining 5% were 31–52
year old individuals (Table 1). The present commer-
cial catch targets 14–22 year old individuals from
1966 to 1974 spawnings. Catches in the near future
will be based on fish spawned between 1970 and
1978.
The size of the beluga population in the Caspian
Sea is small, and the number of fish migrating into
the Volga River is low. The commercial catch of be-
luga is expected to remain low because conditions
in the Caspian Sea are unfavorable (see below).

1st-time-spawners 30 34 41 35

2nd-time-spawners 67 60 50 60

Older individuals 3 6 7 5

Stellate sturgeon

1st-time-spawners 20 4 6 12

2nd-time-spawners 70 80 72 51

Older individuals 10 16 22 37

1st-time-spawners 9 14 10 14

Older individuals^28121412

Russian sturgeon

2nd-time-spawners 63 74 76 74