Spawning induction and
hormonal levels during final oocyte maturation in the silver perch (Bidyanus
bidyanus)
B. Levavi-Sivan, R. Vaiman, O. Sachs, I. Tzchori-2004
Aquaculture, 229(1-4): 419-431
Abstract:
The silver perch (Bidyanus bidyanus Mitchell)
(Teraponidae), is a native Australian freshwater fish that, due to its high
potential for aquaculture, was introduced to Israeli fish farming. The
objective of this study was to find an optimal method for inducing spawning
of silver perch. The agents tested for this purpose were: human chorionic
gonadotropin (hCG; 150 or 200 IU/kg BW); salmon gonadotropin releasing
hormone analogue (sGnRHa at 10, 20, 30, or 40 µg/kg BW); mammalian GnRH
analogue (mGnRHa at 30 µg/kg) and the combination of sGnRHa at 20 µg/kg
and domperidone at 5 mg/kg BW. Based on spawning success and relative
fecundity, sGnRHa at the dose of 30 µg/kg was found to be more efficient
than hCG, mGnRHa or sGnRHa with domperidone. Since domperidone does not
improve the GnRHa effect on final oocyte maturation (FOM) and spawning, it
is suggested that the dopaminergic inhibition during the stages of FOM in
the silver perch is weak. Therefore, the use of GnRHa alone is sufficient to
induce spawning in this fish. Immunoreactive gonadotropin (IR-GtH) and
estradiol levels increased after a single injection of sGnRHa, and peaked
after 24 h. Plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one
(17,20-P) also increased significantly 24 h after the injection of mGnRHa,
12 h before spawning, suggesting that 17,20-P is the maturation-inducing
steroid in silver perch. In order to reveal whether the heterologous
gonadotropin may elicit an immunological reaction, silver perch was
subjected to prolonged treatment with hCG. This treatment resulted in no
detectable titer of antibodies against the mammalian gonadotropin. In
conclusion, although hCG has no deleterious effects in this fish, and is the
more commonly used for spawning induction, sGnRHa at 30 µg/kg is the
recommended treatment for spawning induction of female silver perch under
the conditions prevailing in Israeli aquaculture.