Effect of light intensity on
maturation and spawning of ablated female Penaeus merguiensis
T. Hoang, S.Y. Lee, C.P. Keenan, G.E. Marsden-2002
Aquaculture, 209(1-4) : 347-358
Abstract:
The effect of three levels of light intensity
(BRIGHT: 1100 lux; DIM: 2 lux; and DARK: 0 lux) on ovarian maturation and
spawning of Penaeus merguiensis was investigated. The proportion of
spawners, latency period, spawning rate, fecundity, spawning interval and
number of days spent at stage IV per spawn were not significantly different
(P>0.05) among the three light intensity treatments. Compared to
dim light, bright light did not adversely affect the maturation and
reproductive performance of ablated prawns. However, the percentage of
spawning at stage III (31.6%) and mortality (26.7%) were significantly
higher in the DARK treatment (P<0.05). A trend of increasing
fecundity with an increase in light intensity was observed. Also, the
hypothesis of whether the prawn eye is the only light receptor involved in
ovarian maturation and spawning was tested by covering the remaining eye of
ablated prawns with prepared caps made from black heat-shrinkable tubing
(polyolefin). These prawns were held under 1100 lux (BRI-COV treatment) and
2 lux (DIM-COV) with the DARK treatment as the control group. The proportion
of spawners was lowest in the BRI-COV treatment and highest in the DARK
treatment (P<0.05), whereas there was no significant difference
between these two treatments and the DIM-COV treatment. The DARK treatment,
however, had a significantly higher spawning rate (P<0.05). The
significantly higher percentage of spawning at stage III and less time spent
at stage IV per spawn of prawns in the DARK treatment (P<0.05)
compared with the DIM-COV and BRI-COV treatments suggest that the prawn eye
may not be the only light receptor involving in ovarian maturation and
spawning in P. merguiensis.