el had decreased by16.4 in by the end of 1993.Water
volumedecreasedmorethanthreetimes. and now it
is lessthan 300 km^3. The size of the sea wasreduced
from65.4 to30.0thousand km^2 , and the shoreline
receded in someplaces by 100 km ormore. The
southern brackish-water Adjibaiskii, Muynakskii,
Sarbas,Abbas, andZhaltyrbasbays,whichdifferent
fishes used asspawningareas, are at presentdry.
By 1987 theAral Sea wasdivided by asand bar
into twobasins, the Bolshoe(Large) and Maloe
(Small)seas (Figure 1). The Bolshoe Seareceives
water from the Amu DaryaRiver: thedrainage
wastewaterfrom theirrigatedarea to the south
from theAral Seaalso goesintothis basin. The bed
in the mouthpart of the SyrDaryaRiver hasbeen
changed and it nowentersinto the MaloeSea.
At present, bothrivers aredisconnectedfrom the
AralSea: the SyrDaryaRiver has notreached the
sea since1975, and the AmuDarya,since1982. Con-
nection of theAinu DaryaRiver with the sea was
firstinterrupted in themiddle1970s,when the vol-
ume of the riverwater upstream from theTakhia-
tash Damdecreased tosuch anextent thatwater
was fullywithdrawn for irrigation and no down-
streamflowtookplace.Afterthis, thedelta of the
river considerably changed. Regulated flows of
clearwater(historicallywater in the AinuDarya
River wasextremelymuddy) from theTuyamuyun
Reservoir causeddeepening of theriver bed by 4–5
in or morebelow thedam. Watergoes to the sea
through asystem of smalllakes located in the nat-
ural bed of the river and in the former seabays. The
artificiallyregulateddischarge volume ofwater is
extremely small. The sealevelcontinues to de-
crease and its watersalinityincreases.
As a consequence of alltheseevents,fishing in
the Aral Seastopped in1984. Atpresent,practically
all endemicfishspecieshaveperished. Theywere
replaced by thespeciesintroduced in the1960s.
such asHypophthalmichthysmolitrix,Aristichthys
nobilis, Parabramisperkinensis, Ctenopharyngo-
don idella,and others (Zholdasova et al.1991).
Due to the contemporarylevel ofwater in the Aral
Sea, aswell as in the Amu and SyrDaryarivers,there
is no hope thatpopulations ofanadromousfishes, in-
Acipenserid endemics of theAral Seabasin under
conditions of the environmental disaster: biology
and statusThe largeshovelnosesturgeonThe large Amu-Daryashovelnosesturgeon,Pseu-
doscaphirhynchusKaufmanniis an endemic of the
Amu DaryaRiver. It is anendangeredspecies on
the verge ofextinction. It was included in theUzbek
SSR Red DataBook^3 and in the USSR Red Data
Book^4. Until the1960s, itinhabited the AinuDarya
Riverfrom itssource to its mouth(Nikolskii1938,
Tleuov &Sagitov1973).
The major part of thelarge shovelnosesturgeon
population was located in thefoothill andvalley ar-
cas of the river.Sturgeonwerelargelyconcentrated
near thevillages ofKerki-Chardzhou-Ildzhik in the
upper andmiddle reaches of theriver andwere
caughttherecommercially in the 1930s.Pseudosea-
phirhynchusKaufmanniwas alsonumerous in the
lowerreaches of the AmuDaryaRiver. In thelate
1970s,largeshovelnosesturgeonjuveniles constitu-
ted up to 26% of all youngfish in thelowerreaches
of the Amur Darya River (Tleuov 1981). Pseudosca-
phirhynchuskaufmanniinhabitedsmallirrigation
channels connectedwith theriver aswell.Although
it is a freshwater species, the shovelnosesturgeon
can toleratesomesalinity: it wasfound in thenear-
mouth area of the Aral Sea insalinity 8.5‰(Gos-
teeva1953).
At present,this species ispreservedonly in the
middlereaches of the AmuDaryaRiver. Studies
carried out in 1989 after a 15-yearbreak (Zholdaso-
va et al. 1990) and in 1991 (togetherwithSergei Ga-
malei, MoscowAquarium, Russia)showed that
large shovelnose sturgeon arestillconcentrated in
theirusualhabitats in themiddle reaches of the riv-
er, within a regionbetween the two towns ofKerki
and Chardzhou. This species was not reported
downstreamfromChardzhou in1989 and in 1990 -
1991 (Zholdasova et al.1991).Sturgeonwere also(^3) Uzbek SSR RedDataBook.1983.Vol. 1. Vertebrates.FAN,
(^4) USSR RedDataBook.1984. Vol. 1.Lesnaya Promyshlennost,
Moscow. 390 pp. (inRussian).
Tashkent. 128 pp.(in Russian),
cluding the shipsturgeon,could berestored.