The rest of the catch (8%) was taken upstream from
Ekaterino-Nikolslaya village. Differences in the
catch were due mostly to regional differences in the
abundance of sturgeons.
Now, the lower Amur population of the Amur
sturgeon comprises about 95 000 fish greater than
age two years and is approximately half as large as
the population in the middle Amur. The Zeya and
Bureya population of the Amur sturgeon is ex-
tremely small and on the verge of extinction.
lf the decrease in Amursturgeon populations
continues, then the survival of this species is in
doubt, especially the population inhabiting the mid-
dle Amur.cytes degenerate, then the age of the first matura-
tion, as in kaluga, can be delayed by two to four
years (Svirskii 1979). Total fecundity of Amur stur-
geons is approximately one-fourth that of kaluga: in
317 females 8 to 45 years old, the mean fecundity per
female was 287 780 ± 24 489 eggs (from 41 000 to
1 057 000 eggs in 388 females). The relative fecundi-
ty, however, is much higher than that ofkaluga,
from 4600 to 17 300 eggs kg–1of body weight.
Both morphs begin to migrate to the spawning
grounds in autumn. During winter, the gonads of
80% of the future spawners have not yet reached
stage IV. A few sexually immature fish migrate from
the estuary into the Amur River, where they live
until the completion of sexual maturation. They re-
turn to the estuary only after spawning, one or two
years later.
Amur sturgeon migrate to the spawning grounds
in small groups of 3–5 fish. Spawning takes place in
the spring within 25–30 days at all spawning Since the fall of the Soviet Union, poaching in the
grounds of the lower Amur. Gray morphs of the Amur River has increased enormously. Fishermen
Amur River spawn at the same spawning grounds catch fish now not only for food but also for sale. In
as kaluga, and during spawning, a small number of the lower Amur, intensive fishing of kaluga and
kaluga-Amur sturgeon hybrids are produced Amur sturgeon migrating to spawning grounds
(2–5% of all larvae; Figure 2d). The hybrids are pre- started in 1991. The catch increased both on the
dominantly males (up to 79%). Some hybrids may Russian and Chinese banks of the Amur River, de-
reach 1.9 m in length and 70 kg in weight. spite the ban on fishing issued in 1958.
The embryo period lasts from 83 to 295 hours at The middle Amur populations of both kaluga
240 C and 12° C, respectively(about the same time and Amur sturgeon are especially overfished dur-
as kaluga). The transition of free embryos to active ing their spawning migrations and on the spawning
feeding takes8.5days at 18–20°C, i.e., 1.0–1.5 days grounds. In the upper region of the lower Amur
earlierthanin kaluga (Svirskii 1976a). Amurstur- River, illegal fishing is carried out not only by single
geon survive early development two or three times fishermen but alsobyorganized groups. Chinese
more successfully than do kaluga. fishermen alone caught approximately 410 metric
tons of kaluga and Amur sturgeon in 1989, and 170
metric tons in 1993, taking migrating kaluga and
Amur sturgeon at the prespawning state. Caviar
produced was exported to the United States and
other countries. There is no agreement between
Russia and China regarding sturgeon fishing in the
Amur River. Russians started a sturgeon fishery in
the lower region of the middle Amur in1991, and by
1993, had taken more than 200 metric tons of kaluga
and Amur sturgeon migrating into the middle reach
of the Amur River for spawning, although official
records indicated 64.4 metric tons in 1991,62.6 met-
ric tons in 1992, and 47.8 metric tons in 1993. In the
General comments on the status of kaluga and
Amur River sturgeonComtemporary statusThe current size of the estuary population of Amur
sturgeon is relatively low: about 3000 fish are older
than 2 years in the estuary. In 1891, when the catch of
the Amur sturgeon in the Amur River Basin reach
ed 607 metric tons, the fish caught in the lower
Amur and estuary constituted only about 3% of the
whole annual catch (kryukov1894). Most fish
(89%) were caught in the middle Amur, from Eka-
terino-Nikolskaya village to Tambovskaya village.