Off-season maturation and
spawning of Penaeus semisulcatus by eyestalk ablation and/or
temperature–photoperiod regimes
M. Aktaş, M. Kumlu, O.T. Eroldogan-2003
Aquaculture, 228(1-4): 361-370
Abstract:
In this study, nine different treatments were tested
on off-season reproductive performance of Penaeus semisulcatus for 60
days in a recirculating system, in round tanks (1.2-m diameter) situated in
a greenhouse. A combination of raised temperature (28 °C) and shortened (10
h) or increased day length (14 h) was not sufficient to induce maturation in
unablated females of P. semisulcatus. Unablated females showed no
sign of ovarian development at a constant low temperature of 20 °C. Cyclic
fluctuation (period of 10 days) of water temperature (20–28 °C) at local
winter photoperiod regime (10-h illumination) induced successful maturation
and even multiple spawnings within the same moulting period. Natural
daylight supplementation (14-h illumination) did not produce any advantage
over natural illumination (10 h). Unilateral eyestalk ablation had the most
profound effect on the induction of ovarian development and spawning in this
species. Even at a temperature of 20 °C, eyestalk-ablated females developed
their ovaries up to the 4th stage but with still no spawning. It appears
that P. semisulcatus requires not only optimal environmental
conditions but also a certain stimulus such as ablation or temperature
fluctuation for successful maturation and spawning in captivity during the
winter season. Small tank size (1.2 m in diameter) did not inversely affect
mating success of P. semisulcatus at the sex ratio of 1:2 male/female
and 10 shrimp/m2 stocking density. The present results have
demonstrated that eyestalk ablation or cyclic temperature fluctuation
techniques can successfully be applied to obtain off-season spawning from P.
semisulcatus broodstock in the sub-tropics.
(Faculty of Fisheries, Mustafa Kemal University,
Antakya, Turkey, e-mail of M. Kumlu: mkumlu@cu.edu.tr)