360
M. 'v0ñ'Lukowicä etai.
productivity. The tench is very useful when stocked in ponds that are
Ï
overgrown with plants and filled with mud that high carp yields cannot
expected. These ponds are better utiljzed by tench. Communal rearing
pike is often successful because pike likes a similar habitat. Tench f
_
spawners are st0ckèd together with advanced pike fry which feed on
offSpring, thus regulating the entire stock and individual growth.
j
usually brings a better price on the market than carp.
j
'
4. Basic features of reproduction and fry rearing
The tench female reaches sexual maturity when 3 or 4 years old, but
‘
sometimes at 2 years, while the male is mature at 2 to 3 years. The
-
are distinguished by the size and structure of the pelvic fins, which
the male are larger and have a thickened second ray. Spawning time can
Î
extend from May to August at a water temperature of 20°C and above. In
;
'
central Europe, spawning takes place preferably in July.
-
The tench is a sequential spawner. Morawska (l984) found that
patterns over the prespawning and spawning period exerted a determining
effect on the yield of reproduction and the number of eggs per batch and
thus on fecundity during the season. In heated ponds, the reproductive
'ÿ
season
began one month earlier and the tench deposited 5 to 8 batches of
spawn; in the control ponds, only 3.to 4 were deposited. The number of eggs
deposited by females from heated ponds was, on the average, about 40 to 90%
higher. Also, certain properties of the milt, such as sperm motility, number
1
of spermatozoa and milt density, were found to depend on water temperature
(Zuromska,‘l98ll. High temperatures above 25°C and their sudden increaSe
had an unfavourable influence on both the condition of the males and milt
quality.
“
Tench females give 80 000 to l20 000 eggs/l kg of body weight (egg diameter;
0.4—0.5 mm) immediately after spawning; When swollen the eggs are
in_diameter (Horvath and
with…a live- wei;ght
000.
a
diameʀr of
to l:0 mm »Ihe eggs ae Sticky and affix to
plants. They hatch within about 3«daysmat temperature5wof 22 to
jŸ}
t0
:ç
_
The
lË
sac
is
few days later. The first food must be very small
natural COnditions, rotifers are
(e;g. crustaceans) are also accepted. EVert (l974)7fOUnd the followfng“
growth‘fiçUres:
mm at 7 days, 5.8-6.3 mm at 12 days, 10.0—l4.7 mm
at 25 days .“
_.
___
,__…j
_
Tenchcan reproduce inwarmpondsw1th submergedvegetat1on
_
or …
‘
a‘ŒŸŒC‘aJ $Pawmng. grounds…(branchesbfŸjjuh1‘peror“
thèÿïf"
have
onmarshyand sandyso11 Some of… the.
The
probiem1n small Dub1schtype Ponds1s howto co11 ect thet1ny
fry & few days after hatehihg. Therefore, in Conventional pond farms tench
M. 'v0ñ'Lukowicä etai.
productivity. The tench is very useful when stocked in ponds that are
Ï
overgrown with plants and filled with mud that high carp yields cannot
expected. These ponds are better utiljzed by tench. Communal rearing
pike is often successful because pike likes a similar habitat. Tench f
_
spawners are st0ckèd together with advanced pike fry which feed on
offSpring, thus regulating the entire stock and individual growth.
j
usually brings a better price on the market than carp.
j
'
4. Basic features of reproduction and fry rearing
The tench female reaches sexual maturity when 3 or 4 years old, but
‘
sometimes at 2 years, while the male is mature at 2 to 3 years. The
-
are distinguished by the size and structure of the pelvic fins, which
the male are larger and have a thickened second ray. Spawning time can
Î
extend from May to August at a water temperature of 20°C and above. In
;
'
central Europe, spawning takes place preferably in July.
-
The tench is a sequential spawner. Morawska (l984) found that
patterns over the prespawning and spawning period exerted a determining
effect on the yield of reproduction and the number of eggs per batch and
thus on fecundity during the season. In heated ponds, the reproductive
'ÿ
season
began one month earlier and the tench deposited 5 to 8 batches of
spawn; in the control ponds, only 3.to 4 were deposited. The number of eggs
deposited by females from heated ponds was, on the average, about 40 to 90%
higher. Also, certain properties of the milt, such as sperm motility, number
1
of spermatozoa and milt density, were found to depend on water temperature
(Zuromska,‘l98ll. High temperatures above 25°C and their sudden increaSe
had an unfavourable influence on both the condition of the males and milt
quality.
“
Tench females give 80 000 to l20 000 eggs/l kg of body weight (egg diameter;
0.4—0.5 mm) immediately after spawning; When swollen the eggs are
in_diameter (Horvath and
with…a live- wei;ght
000.
a
diameʀr of
to l:0 mm »Ihe eggs ae Sticky and affix to
plants. They hatch within about 3«daysmat temperature5wof 22 to
jŸ}
t0
:ç
_
The
lË
sac
is
few days later. The first food must be very small
natural COnditions, rotifers are
(e;g. crustaceans) are also accepted. EVert (l974)7fOUnd the followfng“
growth‘fiçUres:
mm at 7 days, 5.8-6.3 mm at 12 days, 10.0—l4.7 mm
at 25 days .“
_.
___
,__…j
_
Tenchcan reproduce inwarmpondsw1th submergedvegetat1on
_
or …
‘
a‘ŒŸŒC‘aJ $Pawmng. grounds…(branchesbfŸjjuh1‘peror“
thèÿïf"
have
onmarshyand sandyso11 Some of… the.
The
probiem1n small Dub1schtype Ponds1s howto co11 ect thet1ny
fry & few days after hatehihg. Therefore, in Conventional pond farms tench