135
an increase in blue-green algae resulted in ‘water
blooms’. The lake bottom also became covered in
clay. This was accompanied by an increase in the
biomass and production of zooplankton and
bottom- dwelling chironomids and oligochaetes.
Fish yield rose from 10.0 to 20.9 kg ha
−1 in the
second half of the 1970s. There was a dramatic
change in fi sh species dominance. Sevan trout
stocks declined sharply, while the introduced
whitefi sh increased from 166.1 t in 1960 to 846.3 t
in 1973. Further, poaching also takes a substantial
blame for the reduction in the stocks of Sevan
trout. With the fall in water level, spawning
grounds of Sevan khramulya were disappearing.
Changes in Fish Catches
Before the water level in Lake Sevan started to
fall, ‘winter’, ‘summer’ and ‘gegarkuni’ trouts
dominated the catches, while Bodzhak trout was
less common. In 1970, gegarkuni trout dominated the catches with 120 t per year, followed by
the ‘summer’ trout.
Hatchery Production of Stocking Material
Stocking of trout produced from hatcheries
started in 1923 when 1.4 million trout larvae
were released in the lake. The main objective was
to increase the abundance of gegarkuni trout and
‘summer’ trout. Two trout hatcheries were producing larvae on a large scale for releases in rivers and streams feeding the lake.
Lake Sevan as Source of Stocking Material
for Other Waterbodies
Regardless of the critical reduction in Sevan trout
stocks, the fi sh management programme still uses
the lake as a source of fi sh for stocking other waterbodies. Sevan trout has been introduced in the
Ukraine, Kyrgyzstan and Karelia. More than 10
million eggs of whitefi sh are collected every year
from inshore waters to be transferred to lakes of the
Urals, Central Asia, Siberia and Georgia. Further,
Khramulya is transferred to waterbodies in Georgia
and the Moscow and St. Petersburg regions.
Other Coldwater HA Lakes of the Caucasus
In addition to Lake Sevan, a number of other
lakes in the Caucasus have fi shery potential.
Lake Karagel (altitude 3,195 m; 16.8 ha), also
in Armenia, although considered of no fi shery
importance, has Sevan trout ( Salmo ischchan )
which was stocked.
Lake Arpagel (2,021 m; 2,200 ha) has common carp fi shery, and its fi shery production
potential is estimated to be 20–40 t year
−1
(Kasymov 1972 ).
In Georgia, Kasymov ( 1972 ) and Chkhaidze
( 1981 ) mentioned 10 lakes of 30 ha to 3,688 ha
surface area with fi shery importance.
Lake Khanchali (altitude 1,930 m, surface
area 1,375 ha) is so shallow that it freezes almost
down to the bottom. This lake, however, has a
potential fi shery production of 275 t year
−1 if part
is converted to ponds or if regularly stocked.
Lake Tabiskuri (1,990 m; 1440 ha) has trout
and two species of coregonids. Its potential fi sh
production is estimated at 100 t year
−1 .
Lake Sagamo (1,994 m; 496 ha) has trout,
carp, khramulya ( Varicorhinus capoeta ), chub
( Leuciscus cephalus ), coregonids and several
other fi sh species. The lake’s fi sh production
potential is estimated to be 40 t year
−1 .
Khramulya is an indigenous fi sh in Georgia, it
easily adapts to various environments and to different types of food, and it also has a nice tasting
fl esh. In Georgia, it has already been successfully
tested in aquaculture conditions (Verulashvili
1981 ).
Lake Bazaleti (879 m; 124 ha), with no fi shery
at present, has a fi shery production potential of
3.6 t year
−1
.
Lake Madatapa (2,108 m; 885 ha) has been
considered for the production of the Paravan race
of common carp.
Lake Paravan (2,060 m; 3,680 ha) has common carp, khramulya, chub and coregonids, and
its fi sh production potential is estimated to be
352 t year
−1
.
Lake Bareti (1,587 m; 155 ha) has not been
considered yet for fi shery production.
For effi cient management of lakes and reservoirs in Georgia, Chkhaidze ( 1981 ) had estimated that 38 million fry/fi ngerlings are
needed.
In Abkhazia, Lake Bebesini (159 ha) fi sh
production potential is estimated to be
6.9 High Altitude (HA) Lentic Bodies
an increase in blue-green algae resulted in ‘water
blooms’. The lake bottom also became covered in
clay. This was accompanied by an increase in the
biomass and production of zooplankton and
bottom- dwelling chironomids and oligochaetes.
Fish yield rose from 10.0 to 20.9 kg ha
−1 in the
second half of the 1970s. There was a dramatic
change in fi sh species dominance. Sevan trout
stocks declined sharply, while the introduced
whitefi sh increased from 166.1 t in 1960 to 846.3 t
in 1973. Further, poaching also takes a substantial
blame for the reduction in the stocks of Sevan
trout. With the fall in water level, spawning
grounds of Sevan khramulya were disappearing.
Changes in Fish Catches
Before the water level in Lake Sevan started to
fall, ‘winter’, ‘summer’ and ‘gegarkuni’ trouts
dominated the catches, while Bodzhak trout was
less common. In 1970, gegarkuni trout dominated the catches with 120 t per year, followed by
the ‘summer’ trout.
Hatchery Production of Stocking Material
Stocking of trout produced from hatcheries
started in 1923 when 1.4 million trout larvae
were released in the lake. The main objective was
to increase the abundance of gegarkuni trout and
‘summer’ trout. Two trout hatcheries were producing larvae on a large scale for releases in rivers and streams feeding the lake.
Lake Sevan as Source of Stocking Material
for Other Waterbodies
Regardless of the critical reduction in Sevan trout
stocks, the fi sh management programme still uses
the lake as a source of fi sh for stocking other waterbodies. Sevan trout has been introduced in the
Ukraine, Kyrgyzstan and Karelia. More than 10
million eggs of whitefi sh are collected every year
from inshore waters to be transferred to lakes of the
Urals, Central Asia, Siberia and Georgia. Further,
Khramulya is transferred to waterbodies in Georgia
and the Moscow and St. Petersburg regions.
Other Coldwater HA Lakes of the Caucasus
In addition to Lake Sevan, a number of other
lakes in the Caucasus have fi shery potential.
Lake Karagel (altitude 3,195 m; 16.8 ha), also
in Armenia, although considered of no fi shery
importance, has Sevan trout ( Salmo ischchan )
which was stocked.
Lake Arpagel (2,021 m; 2,200 ha) has common carp fi shery, and its fi shery production
potential is estimated to be 20–40 t year
−1
(Kasymov 1972 ).
In Georgia, Kasymov ( 1972 ) and Chkhaidze
( 1981 ) mentioned 10 lakes of 30 ha to 3,688 ha
surface area with fi shery importance.
Lake Khanchali (altitude 1,930 m, surface
area 1,375 ha) is so shallow that it freezes almost
down to the bottom. This lake, however, has a
potential fi shery production of 275 t year
−1 if part
is converted to ponds or if regularly stocked.
Lake Tabiskuri (1,990 m; 1440 ha) has trout
and two species of coregonids. Its potential fi sh
production is estimated at 100 t year
−1 .
Lake Sagamo (1,994 m; 496 ha) has trout,
carp, khramulya ( Varicorhinus capoeta ), chub
( Leuciscus cephalus ), coregonids and several
other fi sh species. The lake’s fi sh production
potential is estimated to be 40 t year
−1 .
Khramulya is an indigenous fi sh in Georgia, it
easily adapts to various environments and to different types of food, and it also has a nice tasting
fl esh. In Georgia, it has already been successfully
tested in aquaculture conditions (Verulashvili
1981 ).
Lake Bazaleti (879 m; 124 ha), with no fi shery
at present, has a fi shery production potential of
3.6 t year
−1
.
Lake Madatapa (2,108 m; 885 ha) has been
considered for the production of the Paravan race
of common carp.
Lake Paravan (2,060 m; 3,680 ha) has common carp, khramulya, chub and coregonids, and
its fi sh production potential is estimated to be
352 t year
−1
.
Lake Bareti (1,587 m; 155 ha) has not been
considered yet for fi shery production.
For effi cient management of lakes and reservoirs in Georgia, Chkhaidze ( 1981 ) had estimated that 38 million fry/fi ngerlings are
needed.
In Abkhazia, Lake Bebesini (159 ha) fi sh
production potential is estimated to be
6.9 High Altitude (HA) Lentic Bodies