180
C. F. HICKLING
When I was in Djakarta (then Batavia) in March, 1947, I was told
that the " Heemrad " ponds had produced 4 254 kg of Tilapia and
1 682 kg of grey mullet and prawns in February to March 1947.
B. Russian limans
I n the Russian limans there is hardly any pond management. The
very large size of the limans, often several thousand acres in area,
would make most measures impracticable. As they are mostly shallow,
they warm up early in the spring, and the naturally-spawned fry,
chiefly of the golden grey mullet, Lixa aurata, approach the coasts in
spring at sea temperatures of 5-6"C, and seek to enter the limans,
where the water is slightly warmer. They are able to react to temperature differences of less than 1°C. As they ascend the channels leading
from the sea to the limans, they may be caught and counted, so that
there may be come control over the rate of stocking. If such counts
show that there are insufficient fry, these may be supplemented with
fry bought elsewhere. Other fish also enter, notably the flounder and
atherines. Some small gobies are permanent inhabitants.
At first the young mullet fry, which have their maximum migration
in the latter half of May, scatter along the shores of the liman, especially
where there is a good growth of Zostera and Ruppia.
By day, they browse in these shallow areas, but at night they go
into deeper water. By July, when the fry have grown to small fingerlings, they quit the shallows and feed on the detritus and microbenthos
of the deeper silty bottom of the liman.
Towards autumn, when the temperature of the liman begins to fall,
and when evaporation has lowered the level of the liman below that of
the sea, a current flows down the channel from the sea into the liman,
and the now well-grown fingerlings, or " chulari ", react to this current
by swimming against it up the channel towards the sea. They then
have a maximum weight of about 200 g, though in limans with poor
feeding conditions they may be much smaller ; however, the " chulari "
are marketable a t these sizes.
Meanwhile, during the summer, fences with more or less elaborate
traps will have been put up across the channels, and in these the migrating fish are caught.
Because these fish are still far from maturity when caught, fears
have been expressed for over a century that the main mullet fishery
in the Black Sea may be adversely affected by the capture of these
fish from the limans before they have had the chance to breed. But
Babaian et al. (1967) show that natural fluctuations in the abundance
of the year-classes of grey mullet in the Black Sea far exceed any
C. F. HICKLING
When I was in Djakarta (then Batavia) in March, 1947, I was told
that the " Heemrad " ponds had produced 4 254 kg of Tilapia and
1 682 kg of grey mullet and prawns in February to March 1947.
B. Russian limans
I n the Russian limans there is hardly any pond management. The
very large size of the limans, often several thousand acres in area,
would make most measures impracticable. As they are mostly shallow,
they warm up early in the spring, and the naturally-spawned fry,
chiefly of the golden grey mullet, Lixa aurata, approach the coasts in
spring at sea temperatures of 5-6"C, and seek to enter the limans,
where the water is slightly warmer. They are able to react to temperature differences of less than 1°C. As they ascend the channels leading
from the sea to the limans, they may be caught and counted, so that
there may be come control over the rate of stocking. If such counts
show that there are insufficient fry, these may be supplemented with
fry bought elsewhere. Other fish also enter, notably the flounder and
atherines. Some small gobies are permanent inhabitants.
At first the young mullet fry, which have their maximum migration
in the latter half of May, scatter along the shores of the liman, especially
where there is a good growth of Zostera and Ruppia.
By day, they browse in these shallow areas, but at night they go
into deeper water. By July, when the fry have grown to small fingerlings, they quit the shallows and feed on the detritus and microbenthos
of the deeper silty bottom of the liman.
Towards autumn, when the temperature of the liman begins to fall,
and when evaporation has lowered the level of the liman below that of
the sea, a current flows down the channel from the sea into the liman,
and the now well-grown fingerlings, or " chulari ", react to this current
by swimming against it up the channel towards the sea. They then
have a maximum weight of about 200 g, though in limans with poor
feeding conditions they may be much smaller ; however, the " chulari "
are marketable a t these sizes.
Meanwhile, during the summer, fences with more or less elaborate
traps will have been put up across the channels, and in these the migrating fish are caught.
Because these fish are still far from maturity when caught, fears
have been expressed for over a century that the main mullet fishery
in the Black Sea may be adversely affected by the capture of these
fish from the limans before they have had the chance to breed. But
Babaian et al. (1967) show that natural fluctuations in the abundance
of the year-classes of grey mullet in the Black Sea far exceed any