174
Aquaculture of Cyprinids
relation to the daily cycle of hormones (Peter). Woynarovich summarized his
experience in this subject and indicated that propagation of the common carp
can
take place all year round in tropical countries.
Other external factors affecting reproduction in cyprinids were pointed
out:
stress
and stocking density, feeding (Peteri et al., Wiegand) and
2.
Induced spawning and artificial fertilization
Under natural conditions, a cascade of glands and hormones "translate“
environmental cues to gonadal growth and spawning. The various methods of
spawning induction are, in fact, artificial interventions in one or another
step of this cascade. Classical hypophysation, although sufferring in most
cases
from the lack of standardization, is still a common practice among
carp breeders
(Toor; Dwivedi and
Reddy). Introduction of a calibrated carp
pituitary extract into hatchery practice will, probably, increase predicta—
bility of induced spawning by hypophysation (Yaron). Gonadotropins of mam—
malian origin (HCG), alone or in combination with carp pituitary extract,aree
not more
effective than pituitary extract alone (Epler et al.). The report
by Macinthosh and Price does not conform, however, with this view. Never—
theless, several participants expressed the idea that the use of heterologous
gonadotropins such as HCG for spawning induction may lead to the formation of
antibodies in the recipient fish and interfere with their spawning in sub—
sequent seasons.
The administration of gonadotropin—releasing hormones of
origin (GnRH, LHRH) or their synthetic analogues seems to be a better subs—
titution for the classical hypophysation technique. Their potency in raising
endogenous gonadotropin levels and inducing ovulation in certain cyprinids
was
examined by using them.alone (Kouril) or in combination with the dopamine antogonist pimozide (Raul and Rishi;
Sokolowska et al., Lin et al.).
Nbreover, Kaul and Rishi reported that pimozide, even given alone, was
effective inducer
of ovulation in the mrighal; in other cypriids such effect was not observed. Nevertheless, Woynarovich complained that his experience
with GnRH in characin, fish were not that successful. Pullin remarked
that the cost of treatment with GnRH plus pimozide should be reduced in or—
der to be acceptable in developing countries.
',
.The possible toxicity of pimozide or its residues was raised by Fostier
in
relationship with the welfare of the recipient fish or the consumer. Un—
fortunately, no studies have yet been performed on the biological half—
11fe of pimozide or its residùes in the fish (Peter). The problem.for the
consumers
does not seem to be that severe since females treated for spawning
are
kept usually as a brOQdstock in the hateheriès for subsequent seasons
and are rarely marketèd (Horvath). The paper presented by Lin et al. has
indicated that reserpine, an inhibitor of dopamine secretion, can successfully substitute pimozide in carp induced to spawn by GnRH analogues. Nevertheless,
the effects Of both pimozide and reserpine on egg quality and fish
health 1s yet to be
”
Another aSP€Ct of spawning induction, Whether by pituitary extracts or
by
18
the receptivity or suitàbility of the fish to_the treatment.
fish abdomen for sOftness has been proven to be rather subjec—
tive
and 1naccurate.
Ovarian biopsy and subsequent determination of the poSition of
the germinal vesiÇle (GV)
be a more adequate way to
determine
the suitability of female carp fbr spawning induction. A high pro—
portion (65 % or.m°re)—Of °°CÿteS in which the GV has already started mi—
gration
GV) may serve
for a female ready for
Aquaculture of Cyprinids
relation to the daily cycle of hormones (Peter). Woynarovich summarized his
experience in this subject and indicated that propagation of the common carp
can
take place all year round in tropical countries.
Other external factors affecting reproduction in cyprinids were pointed
out:
stress
and stocking density, feeding (Peteri et al., Wiegand) and
2.
Induced spawning and artificial fertilization
Under natural conditions, a cascade of glands and hormones "translate“
environmental cues to gonadal growth and spawning. The various methods of
spawning induction are, in fact, artificial interventions in one or another
step of this cascade. Classical hypophysation, although sufferring in most
cases
from the lack of standardization, is still a common practice among
carp breeders
(Toor; Dwivedi and
Reddy). Introduction of a calibrated carp
pituitary extract into hatchery practice will, probably, increase predicta—
bility of induced spawning by hypophysation (Yaron). Gonadotropins of mam—
malian origin (HCG), alone or in combination with carp pituitary extract,aree
not more
effective than pituitary extract alone (Epler et al.). The report
by Macinthosh and Price does not conform, however, with this view. Never—
theless, several participants expressed the idea that the use of heterologous
gonadotropins such as HCG for spawning induction may lead to the formation of
antibodies in the recipient fish and interfere with their spawning in sub—
sequent seasons.
The administration of gonadotropin—releasing hormones of
origin (GnRH, LHRH) or their synthetic analogues seems to be a better subs—
titution for the classical hypophysation technique. Their potency in raising
endogenous gonadotropin levels and inducing ovulation in certain cyprinids
was
examined by using them.alone (Kouril) or in combination with the dopamine antogonist pimozide (Raul and Rishi;
Sokolowska et al., Lin et al.).
Nbreover, Kaul and Rishi reported that pimozide, even given alone, was
effective inducer
of ovulation in the mrighal; in other cypriids such effect was not observed. Nevertheless, Woynarovich complained that his experience
with GnRH in characin, fish were not that successful. Pullin remarked
that the cost of treatment with GnRH plus pimozide should be reduced in or—
der to be acceptable in developing countries.
',
.The possible toxicity of pimozide or its residues was raised by Fostier
in
relationship with the welfare of the recipient fish or the consumer. Un—
fortunately, no studies have yet been performed on the biological half—
11fe of pimozide or its residùes in the fish (Peter). The problem.for the
consumers
does not seem to be that severe since females treated for spawning
are
kept usually as a brOQdstock in the hateheriès for subsequent seasons
and are rarely marketèd (Horvath). The paper presented by Lin et al. has
indicated that reserpine, an inhibitor of dopamine secretion, can successfully substitute pimozide in carp induced to spawn by GnRH analogues. Nevertheless,
the effects Of both pimozide and reserpine on egg quality and fish
health 1s yet to be
”
Another aSP€Ct of spawning induction, Whether by pituitary extracts or
by
18
the receptivity or suitàbility of the fish to_the treatment.
fish abdomen for sOftness has been proven to be rather subjec—
tive
and 1naccurate.
Ovarian biopsy and subsequent determination of the poSition of
the germinal vesiÇle (GV)
be a more adequate way to
determine
the suitability of female carp fbr spawning induction. A high pro—
portion (65 % or.m°re)—Of °°CÿteS in which the GV has already started mi—
gration
GV) may serve
for a female ready for