236
J. Nabhitabhata
or lying on the substrate. The prey is seized with the tentacles and kept within their
arms. When the cuttlefish are fed on dead food, they change their feeding behaviour
to use only arms to seize prey without the positioning step in the feeding behaviour.
Tang and Khoo (1974) also reported the same change and suspected it was a sign
of weakness. This change indicates the success of training, and that the spineless
cuttlefish are accustomed to the feed and culture conditions (human appearance
with feed and the environment of the culture tank). Another reason for the change in
behaviour is the lack of motion of dead feed compared to the active live food. It is
unnecessary for the spineless cuttlefish to use a rapid and energy consuming motion
like stretching out the tentacles to capture the dead feed. This kind of behavioural
change is similar to that seen in cultured pharaoh cuttlefish, S� pharaonis. Aggressive behaviour is prominent at this age and cannibalism is observed whenever the
food is in short supply. Males sometimes bite other males in connection with their
sexual activity (Nabhitabhata et al. 1984).
Tanks of any size can be used for the ongrowing phase of the spineless cuttlefish.
The initial stocking density of this phase, after 30 days, is 30 individuals m
−2
. Size
grading is performed every 10–20 days until ceasing at the beginning of reproduction, at about 70 days. Feeding is twice per day at the ration of 10 % of body weight.
Food with high nutritional value, i.e. whole shrimps, large mysids, with additional
cost, may be added as a supplement. Survival is cumulative, and of 80–90 % during
ongrowing (Table 13.2).
Ongrowing of S� inermis in an earthen pond has been studied in Thailand
(Nabhitabhata et al. 1985). Cuttlefish accustomed to the dead feed, of about 38 mm
mantle length and 11 g weight (50–60 days) were released into a pen covering an
area of 45 m
2
in a large (25,600 m
2
) earthen pond at 3–6 individuals m
−2
. Survival
was of 40 % after 50 days. The production was about 4,000 g and the feed conversion efficiency was of 13–18 %. One explanation for this low survival was the low
quality of the benthic substrate in the pond, which lowered the water quality and
initiated bacterial infections. Another problem was a competing fish, Therapon spp.
that had infiltrated the pen through the net fence. Those fish were more active than
the cuttlefish, interfering in the ritual feeding and resting of the cuttlefish.
13.6.2 Growth
The relationship between mantle length and weight in the ongrowing phase after
30 days is also expressed with the power equation (Nabhitabhata 2002) (Fig. 13.6):
4
2.704
W 5.200 10 ML
−
=
×
(13.4)
The slope of the length–weight relationship equation obtained from cultured batches is
2.0–2.7 which is within the range of 1.9–2.7 obtained from natural stocks (Chotiyaputta 1981; Unnithan 1982; Sundaram and Khan 2011). The second growth phase in terms
of mantle length–age relationship of the cuttlefish from 30 days old, the inflection
point (Fig. 13.7), is expressed with the logarithmic regression (Nabhitabhata 2002):
J. Nabhitabhata
or lying on the substrate. The prey is seized with the tentacles and kept within their
arms. When the cuttlefish are fed on dead food, they change their feeding behaviour
to use only arms to seize prey without the positioning step in the feeding behaviour.
Tang and Khoo (1974) also reported the same change and suspected it was a sign
of weakness. This change indicates the success of training, and that the spineless
cuttlefish are accustomed to the feed and culture conditions (human appearance
with feed and the environment of the culture tank). Another reason for the change in
behaviour is the lack of motion of dead feed compared to the active live food. It is
unnecessary for the spineless cuttlefish to use a rapid and energy consuming motion
like stretching out the tentacles to capture the dead feed. This kind of behavioural
change is similar to that seen in cultured pharaoh cuttlefish, S� pharaonis. Aggressive behaviour is prominent at this age and cannibalism is observed whenever the
food is in short supply. Males sometimes bite other males in connection with their
sexual activity (Nabhitabhata et al. 1984).
Tanks of any size can be used for the ongrowing phase of the spineless cuttlefish.
The initial stocking density of this phase, after 30 days, is 30 individuals m
−2
. Size
grading is performed every 10–20 days until ceasing at the beginning of reproduction, at about 70 days. Feeding is twice per day at the ration of 10 % of body weight.
Food with high nutritional value, i.e. whole shrimps, large mysids, with additional
cost, may be added as a supplement. Survival is cumulative, and of 80–90 % during
ongrowing (Table 13.2).
Ongrowing of S� inermis in an earthen pond has been studied in Thailand
(Nabhitabhata et al. 1985). Cuttlefish accustomed to the dead feed, of about 38 mm
mantle length and 11 g weight (50–60 days) were released into a pen covering an
area of 45 m
2
in a large (25,600 m
2
) earthen pond at 3–6 individuals m
−2
. Survival
was of 40 % after 50 days. The production was about 4,000 g and the feed conversion efficiency was of 13–18 %. One explanation for this low survival was the low
quality of the benthic substrate in the pond, which lowered the water quality and
initiated bacterial infections. Another problem was a competing fish, Therapon spp.
that had infiltrated the pen through the net fence. Those fish were more active than
the cuttlefish, interfering in the ritual feeding and resting of the cuttlefish.
13.6.2 Growth
The relationship between mantle length and weight in the ongrowing phase after
30 days is also expressed with the power equation (Nabhitabhata 2002) (Fig. 13.6):
4
2.704
W 5.200 10 ML
−
=
×
(13.4)
The slope of the length–weight relationship equation obtained from cultured batches is
2.0–2.7 which is within the range of 1.9–2.7 obtained from natural stocks (Chotiyaputta 1981; Unnithan 1982; Sundaram and Khan 2011). The second growth phase in terms
of mantle length–age relationship of the cuttlefish from 30 days old, the inflection
point (Fig. 13.7), is expressed with the logarithmic regression (Nabhitabhata 2002):