308
L. Väradi
However,
for
long—distance transport,
the
method
must
be
combined
with
me—
chanical
or
electrical
herding methods.
Open
drainage
canals
are
proposed
for
these
systems
because
carp
tend
to
remain
inside
the
dark
underground
pipe.
Hydraulic herding can be improved by an intake of fresh,
oxygen—rich
water
into
the
catch—basin
that
attracts
the
fish.
They react to the fresh—
water
current
from
several
hundred
meters,
especially when the water level
is
low
in
the pond.
Electric grids or electrified seines are also used for driving the fish
to
t€_Eâ%EEîBëEîä_ËËSE_ËEE_EEEŒËEÎÎÇ“Erained pond or more often from the
drainage canal. These devices are not common in pond fish farms because they
are
fairly complicated to operate and depend on varying physical and chemi—
cal
parameters
(especially conductivity) of the water.
ln
the
Soviet Union,
a
special floating electric grid has been developed for herding (Tjuktjaeva
and
Lisenko,
1974).
The
gasoline
motor—operated
device
with
4
kw
capacity
has
a
useful
57—m2
water
cross—section
at
40 millisiemens/m water conducti—
vity.
However
it
decreases
to
about
27
m2 when
conductivity increases to 80
millisiems/m.
The
electrified seine was
developed and tested in farming con—
ditions
in
Hungary but was not well accepted by fish farms due to the rea—
sons
mentioned above.
il.
CATCHING
Lifting the fish out of the catch—basin is a critical process because
gentle
handling is required when they are separated from their natural me—
dium.
Moreover,
this
process
has
to be
coordinated with driving the fish in—
to
the
catch—basin,
sorting and transport.
Fish
lifts
can
be
divided
into
;wo
major types : mechanical and hydraulic.
A.
Mechanical
fish lifts
These
can
work
intermittently like the mechanized dip net and bucket
elevator
or
continuously like the conveyor belt and fish screw. Small, mobi—
le mechanized dip nets, designed for fish farms and with a lifting height of
about
3—4
m
and
a
capacity of up to 100 kg, are commonly used in some Euro—
pean
countries.
Larger wheel
loaders
and
cranes
can
also
be
used
as
fish
lifts when a dip net is mounted on the boom of the machine.
Bucket
elevators
are
used
in
several
carp
farms.
In
Israel,
a
mobile
elevator
is
used
when
a
trolley containing 50—250 kg of fish is moved on &
10—14 m
long, inclined rail from the catch basin over the embankment (Hephef
and
Pruginin,
1981).
In
Hungary,
stationary elevators are used in some fish
farms where harvesting is fully mechanized. Elevator capacity is 5—6 tons/hJhen
this
equipment is used,
the
fish
may be
injured because they are pres—
sed
together in the dip net or in the bucket in contact with a hard surfa—
ce.
These
problems can be eliminated by the utilization of continuous—opera—
;ion conveyor belts or screws when small amounts of fish are loaded.
Ordinary agricultural conveyor belts are also used as fish lifts but
the
angle
of
the
belt
should
be
no
more
than
30°
C.
These
have
been
used
successfully in Hungary for elevating both common carp and Chinese carp. In
latter
case,
it
was
necessary to mount a special plastic cover over the
oelt.
Specially—desiged conveyor belts and cup conveyors are now available
as
fish lifts.
The length
of the conveyor belts varies between 4 and 16 m and vertical
elevat10n 1s between 2 and 8 m.
Special screw conveyors have been developed
L. Väradi
However,
for
long—distance transport,
the
method
must
be
combined
with
me—
chanical
or
electrical
herding methods.
Open
drainage
canals
are
proposed
for
these
systems
because
carp
tend
to
remain
inside
the
dark
underground
pipe.
Hydraulic herding can be improved by an intake of fresh,
oxygen—rich
water
into
the
catch—basin
that
attracts
the
fish.
They react to the fresh—
water
current
from
several
hundred
meters,
especially when the water level
is
low
in
the pond.
Electric grids or electrified seines are also used for driving the fish
to
t€_Eâ%EEîBëEîä_ËËSE_ËEE_EEEŒËEÎÎÇ“Erained pond or more often from the
drainage canal. These devices are not common in pond fish farms because they
are
fairly complicated to operate and depend on varying physical and chemi—
cal
parameters
(especially conductivity) of the water.
ln
the
Soviet Union,
a
special floating electric grid has been developed for herding (Tjuktjaeva
and
Lisenko,
1974).
The
gasoline
motor—operated
device
with
4
kw
capacity
has
a
useful
57—m2
water
cross—section
at
40 millisiemens/m water conducti—
vity.
However
it
decreases
to
about
27
m2 when
conductivity increases to 80
millisiems/m.
The
electrified seine was
developed and tested in farming con—
ditions
in
Hungary but was not well accepted by fish farms due to the rea—
sons
mentioned above.
il.
CATCHING
Lifting the fish out of the catch—basin is a critical process because
gentle
handling is required when they are separated from their natural me—
dium.
Moreover,
this
process
has
to be
coordinated with driving the fish in—
to
the
catch—basin,
sorting and transport.
Fish
lifts
can
be
divided
into
;wo
major types : mechanical and hydraulic.
A.
Mechanical
fish lifts
These
can
work
intermittently like the mechanized dip net and bucket
elevator
or
continuously like the conveyor belt and fish screw. Small, mobi—
le mechanized dip nets, designed for fish farms and with a lifting height of
about
3—4
m
and
a
capacity of up to 100 kg, are commonly used in some Euro—
pean
countries.
Larger wheel
loaders
and
cranes
can
also
be
used
as
fish
lifts when a dip net is mounted on the boom of the machine.
Bucket
elevators
are
used
in
several
carp
farms.
In
Israel,
a
mobile
elevator
is
used
when
a
trolley containing 50—250 kg of fish is moved on &
10—14 m
long, inclined rail from the catch basin over the embankment (Hephef
and
Pruginin,
1981).
In
Hungary,
stationary elevators are used in some fish
farms where harvesting is fully mechanized. Elevator capacity is 5—6 tons/hJhen
this
equipment is used,
the
fish
may be
injured because they are pres—
sed
together in the dip net or in the bucket in contact with a hard surfa—
ce.
These
problems can be eliminated by the utilization of continuous—opera—
;ion conveyor belts or screws when small amounts of fish are loaded.
Ordinary agricultural conveyor belts are also used as fish lifts but
the
angle
of
the
belt
should
be
no
more
than
30°
C.
These
have
been
used
successfully in Hungary for elevating both common carp and Chinese carp. In
latter
case,
it
was
necessary to mount a special plastic cover over the
oelt.
Specially—desiged conveyor belts and cup conveyors are now available
as
fish lifts.
The length
of the conveyor belts varies between 4 and 16 m and vertical
elevat10n 1s between 2 and 8 m.
Special screw conveyors have been developed