211
lighting, as well as unnatural daily light–dark periods initiated by any human activity, should be avoided. The growth of algae and fungi on the surface of egg capsules
due to excessive light will reduce the hatching rate by blocking the oxygen supply
to the embryo. The attachment of algae also initiates fungal growth on the capsule
membrane and provokes infection of the embryo. The most convenient way to reduce light exposure is curtaining the hatchery with a camouflage net with a lightreducing efficiency of 80 % (Nabhitabhata et al. 2005).
From the baskets, all hatchlings pass through the basket-mesh into the tank.
When the optimum hatchling density in the tank of 500 individuals m
−2
is achieved,
the baskets with the remaining eggs are transferred to another tank of the same water quality. The incubation tank now becomes the nursing tank. The hatchlings are
collected and transferred for nursing into other tanks with extreme caution, in a wet
condition with gentle movement, in order to avoid skin damage. Such skin damage
can subsequently cause mortality, so it could be more appropriate to transfer egg
capsules rather than the hatchlings. (For details, see also Chap. 7 “Aquaculture to
Restocking”, this volume).
12.5 Nursing of Young
12.5.1 Hatchling Characteristics
The overall external morphology and behaviour of the hatchling are similar to that
of the adult. Burrowing behaviour in sandy and small gravel substrata is observed
at 4 days after hatching. Cuttlefish are solitary in habit, lying or burrowing in the
substratum. Gregarious behaviour is occasionally observed when fleeing from a
common enemy or in pursuit of prey in the same direction and feeding together in a
group after about 10 days after hatching. Such group behaviour is beneficial for the
training period during which they feed on dead prey.
12.5.2 System Requirements and Management
Hatchlings of S� pharaonis are benthic and the water depth and density settings
in this phase have to vary in relation to their growth (cuttlefish size), to suit the
management of food. The water depth in tanks is adjusted to encourage aggregation
of the live food organisms. Appropriate biomasses of live feed and cuttlefish in a
tank reduce excess prey search activity and energy expenditure in food hunting,
and hence promote growth. The initial water depth in the egg tanks is lowered from
600 to 300 mm for benthic hatchlings. Instead of lowering the water depth, the egg
baskets are floated inside a hanging net cage of a large, fine mesh (1.5 mm) that is
placed inside a 3,000-L tank (Minton et al. 2001).
12 Sepia pharaonis
lighting, as well as unnatural daily light–dark periods initiated by any human activity, should be avoided. The growth of algae and fungi on the surface of egg capsules
due to excessive light will reduce the hatching rate by blocking the oxygen supply
to the embryo. The attachment of algae also initiates fungal growth on the capsule
membrane and provokes infection of the embryo. The most convenient way to reduce light exposure is curtaining the hatchery with a camouflage net with a lightreducing efficiency of 80 % (Nabhitabhata et al. 2005).
From the baskets, all hatchlings pass through the basket-mesh into the tank.
When the optimum hatchling density in the tank of 500 individuals m
−2
is achieved,
the baskets with the remaining eggs are transferred to another tank of the same water quality. The incubation tank now becomes the nursing tank. The hatchlings are
collected and transferred for nursing into other tanks with extreme caution, in a wet
condition with gentle movement, in order to avoid skin damage. Such skin damage
can subsequently cause mortality, so it could be more appropriate to transfer egg
capsules rather than the hatchlings. (For details, see also Chap. 7 “Aquaculture to
Restocking”, this volume).
12.5 Nursing of Young
12.5.1 Hatchling Characteristics
The overall external morphology and behaviour of the hatchling are similar to that
of the adult. Burrowing behaviour in sandy and small gravel substrata is observed
at 4 days after hatching. Cuttlefish are solitary in habit, lying or burrowing in the
substratum. Gregarious behaviour is occasionally observed when fleeing from a
common enemy or in pursuit of prey in the same direction and feeding together in a
group after about 10 days after hatching. Such group behaviour is beneficial for the
training period during which they feed on dead prey.
12.5.2 System Requirements and Management
Hatchlings of S� pharaonis are benthic and the water depth and density settings
in this phase have to vary in relation to their growth (cuttlefish size), to suit the
management of food. The water depth in tanks is adjusted to encourage aggregation
of the live food organisms. Appropriate biomasses of live feed and cuttlefish in a
tank reduce excess prey search activity and energy expenditure in food hunting,
and hence promote growth. The initial water depth in the egg tanks is lowered from
600 to 300 mm for benthic hatchlings. Instead of lowering the water depth, the egg
baskets are floated inside a hanging net cage of a large, fine mesh (1.5 mm) that is
placed inside a 3,000-L tank (Minton et al. 2001).
12 Sepia pharaonis