| Abstract | Three experiments were conducted to investigate the effect
of light intensity, photoperiod, a nd inclusion of artificial sub - strates on the survival, growth, activity and behavior of Penaeus
monad on post- larvae (PL 12 - PL35), each lasting 3 weeks, each
experiment involved an in].ti.al stocking density of 20l?Ls/l in
aquaria containing 501 of water and average conditions of 20ppt
salinity and 28-29°C.
Experiment 1 found that light intensities of 200 lux, 600
lux, 1,800 lux and natural light (over 3,000 lux) did not significantly effect the growth a nd survival of the shrimps. A light
intensity of 600 lux was selected for further study as it is an
easy and economical l eve l of illumination to provide in shrimp
nurseries.
Results of the second experiment which exposed shrimp to
constant l ight intensity (600 lux) but different photoperiods
(0:24, 8: 18, 12 :12, 10:8, and 24:U) revealed that continuous
l ight (21:0) significantly improved the growth of shrimp post- larvae (p<0.01) but did affect their survival . Light acts as
a stimulating factor on the activity a nd behavior of post-larvae,
and in this way h ad a positive indirect affect on the growth of
the shrimps in these experiments . The shrimps attent the average
body weight of 76 . 4mg at PL33, body length of 22mm, total weight
and length gain of 2,838% and 1.10% respectively and the daily
weight arid length gain of 3.5mg a nd 0. 5mm per day .
In Experiment 3, a combination of optimal l ight conditions
(600 lux, continuous illumination) plus artificial substrates
further improved post- larval growth and survival. Various substages were provided singly, or in combination: mixed
gravel/sand; vertical nylon net; horizontal and vertical bamboo
frame s . A combination of sand plus bamboo was the best substrate
combination. The provision of substrates contributed beneficially
to t he growth and survival of the post- larvae by (a) providing
them with ho l ding and hiding surfaces, (b) providing an addition - a l source of food because of the build up of micro - organisms on
the surface of substrates, and (c) indirectly by acting as a
natural bio-filter in t he culture system.
Under optimal lighting conditions (600 lux, continuous
illumination) plus sand a nd bamboo frame substrates, the follow-ing performance was obtained: mean daily weight gain by post- larvae 5.3mg; length gain 0 . 7mm/day; specific growth rate in body
weight: 11.8%/day , and in body length: 3 . 3%/day; total percentage
weight and length gain 1,095% a nd 102% respectively and survival
rate over 2 1 days : 91%. |