237
13 Sepiella inermis
ML = 0.345 lnT 1.007
−
(13.5)
The growth phase in terms of weight–age relationship (Fig. 13.8), in the second
phase, also starts at the inflection point of 30 days, and can be expressed by the
power model:
4 2.461
W 3.830 10 T
−
=
×
(13.6)
After about 60 days, or 40 mm and 10 g, the colour pattern allows sex recognition.
The male colour pattern is dark brown with white and orange spots on the dorsum
along the base line of the fins. The female colour pattern is dark brown, but a lighter
shade than that of the males, with smaller white spots and without orange spots.
S� inermis begin to form mating pairs on and after the age of 60 days, and the first
mating is observed at 70 days old, or 50 mm and 20 g (Table 13.1).
The growth rate of the spineless cuttlefish decreases after reproduction. During the reproductive period from 80 to 130 days of age, growth rates of 0.2–0.7 %
in length and 0.6–2.0 % in weight are reported, compared to those in the previous
phase of 30–80 days of age, 2.0–2.6 % in length and 5–6 % in weight (Nabhitabhata
1997). Most of the mating and spawning of the spineless cuttlefish is observed at
the size of 60 mm mantle length and 40 g weight (90 days). The daily growth rate
in length decreases to lower than 1.0 % on and after 90 days and that in weight also
decreases after 100 days of age. On average, the overall daily growth rate from
hatching to 130 days of age is 2.4 % in length and 5.5 % in weight.
The final size before senescence of this species is mostly attained during 100–130
days and the females are larger than the males. After 130 days, the average mantle
length is approximately 70 mm, while average weight is 50 g. The maximum size
recorded in culture conditions is about 70 mm mantle length and 80 g weight in a
male (126 days) and 80 mm and 65 g (105 days) for a female (Tables 13.1, 13.2)
(Boonprakob et al. 1977a; Nabhitabhata et al. 1984). The lifespan is approximately
120 days, with a maximum of 150 days.
Growth tends to be much faster in culture condition compared to in the wild.
Silas et al. (1985) reported the maximum mantle length of the spineless cuttlefish
to be 125 mm based on the research on the open sea population. Animals attain
29–35 mm mantle length after 6 months, 53–61 mm after 12 months and 74–82 mm
after 18 months. The lifespan is six times longer and growth is approximately fourfold slower than that obtained from culture batches. The culture conditions, i.e. sufficient food availability and stable environmental factors, tend to induce fast growth
and early maturation, as observed in S� pharaonis (see Chap. 12, this volume).
13.7 Trends in Research and Industrial Level
Inbreeding has no negative effect on growth rate and the final size after culture through
three consecutive generations (Nabhitabhata et al. 1984; Nabhitabhata 1997). The
indifferent growth could, in the short term, provide a reliable and continuous supply
13 Sepiella inermis
ML = 0.345 lnT 1.007
−
(13.5)
The growth phase in terms of weight–age relationship (Fig. 13.8), in the second
phase, also starts at the inflection point of 30 days, and can be expressed by the
power model:
4 2.461
W 3.830 10 T
−
=
×
(13.6)
After about 60 days, or 40 mm and 10 g, the colour pattern allows sex recognition.
The male colour pattern is dark brown with white and orange spots on the dorsum
along the base line of the fins. The female colour pattern is dark brown, but a lighter
shade than that of the males, with smaller white spots and without orange spots.
S� inermis begin to form mating pairs on and after the age of 60 days, and the first
mating is observed at 70 days old, or 50 mm and 20 g (Table 13.1).
The growth rate of the spineless cuttlefish decreases after reproduction. During the reproductive period from 80 to 130 days of age, growth rates of 0.2–0.7 %
in length and 0.6–2.0 % in weight are reported, compared to those in the previous
phase of 30–80 days of age, 2.0–2.6 % in length and 5–6 % in weight (Nabhitabhata
1997). Most of the mating and spawning of the spineless cuttlefish is observed at
the size of 60 mm mantle length and 40 g weight (90 days). The daily growth rate
in length decreases to lower than 1.0 % on and after 90 days and that in weight also
decreases after 100 days of age. On average, the overall daily growth rate from
hatching to 130 days of age is 2.4 % in length and 5.5 % in weight.
The final size before senescence of this species is mostly attained during 100–130
days and the females are larger than the males. After 130 days, the average mantle
length is approximately 70 mm, while average weight is 50 g. The maximum size
recorded in culture conditions is about 70 mm mantle length and 80 g weight in a
male (126 days) and 80 mm and 65 g (105 days) for a female (Tables 13.1, 13.2)
(Boonprakob et al. 1977a; Nabhitabhata et al. 1984). The lifespan is approximately
120 days, with a maximum of 150 days.
Growth tends to be much faster in culture condition compared to in the wild.
Silas et al. (1985) reported the maximum mantle length of the spineless cuttlefish
to be 125 mm based on the research on the open sea population. Animals attain
29–35 mm mantle length after 6 months, 53–61 mm after 12 months and 74–82 mm
after 18 months. The lifespan is six times longer and growth is approximately fourfold slower than that obtained from culture batches. The culture conditions, i.e. sufficient food availability and stable environmental factors, tend to induce fast growth
and early maturation, as observed in S� pharaonis (see Chap. 12, this volume).
13.7 Trends in Research and Industrial Level
Inbreeding has no negative effect on growth rate and the final size after culture through
three consecutive generations (Nabhitabhata et al. 1984; Nabhitabhata 1997). The
indifferent growth could, in the short term, provide a reliable and continuous supply