194
available bottom area is of maximum importance. Forsythe et al. (1994) suggested
a density of 20 cuttlefish m
−2
in closed seawater systems at this ongrowing stage
but, despite recognizing that bottom areas are important, no value was provided.
A density of 400 cuttlefish m
−2
is suggested by Forsythe et al. (2002) in 1,800 L
circular tanks and closed seawater system. From this study, performed at rearing
temperatures of 25 °C, this very high density is on the verge of impacting growth
and survival, due to the increase of biomass present in the tanks.
As for densities in flow-through seawater systems, Sykes et al. (2003) suggested
the use of 120 cuttlefish m
−2
and minimum area of about 1,083 cm
2
(in 10 L raceway
tanks), when starting a new juvenile tank with individuals of approximately 5 g. According to these authors, these density and bottom area values are valid for animals
up to 25 g. Likewise, Domingues and Marquez (2010) studied the effects of both
density and bottom areas in open seawater systems (in concrete raceway tanks) and
obtained results that support the use of high-density and large bottom areas (33 cuttlefish m
−2
with an average weight of 9.5 g), registering similar feeding rates (≈ 10 %
body weight d
−1
) but different food conversions. In fact, mortality and growth were
similar between high- and low-density tanks using similar large bottom areas, which
indicate that the bottom area seems to be more important than the density itself.
Independently from the rearing seawater system, density must be decreased and
bottom areas increased while cuttlefish grows. It is suggested that, from 30 DAH to
10 g, the cited values of Sykes et al. (2003) should be used and from this weight and
to maturation (which is temperature dependable) the findings of Domingues and
Marquez (2010) should be considered.
If cuttlefish is reared in earthen ponds, special attention should be paid to the
density and bottom areas, considering the fast growth rates that the species display
and the inability to correctly observe what is happening within the ponds. If the
pond’s carrying capacity and biological limits are reached, cuttlefish mass mortality
and loss of total biomass produced will occur. This will be due to the inability to
clean the pond which will result in a spike in nitrogenous compounds and a drop in
dissolved oxygen. A common observation to detect that this limit is being reached
is to find eaten cuttlefish or cuttlebones in the pond as well as cuttlefish floating or
swimming in the pond’s surface.
11.6.3 Food
According to Warnke (1994), when cuttlefish are fed in a group, individuals hunt
three times faster than when isolated, more food is ingested and feeding hierarchies
are established.
Currently, growout of cuttlefish juveniles is performed with crustaceans as diet,
mainly the grass shrimp—P� varians (Sykes et al. 2006a). This is due to the easiness of collection (logistics) and results obtained with this diet (Sykes et al. 2006a).
Nonetheless, several different food items have been tested throughout the years,
either solely or as mixed diets. Domingues et al. (2001a, b) used the crab C� maenas;
Domingues et al. (2002, 2003b) and Sykes et al. (2006a) used live or frozen P�
A. V. Sykes et al.
available bottom area is of maximum importance. Forsythe et al. (1994) suggested
a density of 20 cuttlefish m
−2
in closed seawater systems at this ongrowing stage
but, despite recognizing that bottom areas are important, no value was provided.
A density of 400 cuttlefish m
−2
is suggested by Forsythe et al. (2002) in 1,800 L
circular tanks and closed seawater system. From this study, performed at rearing
temperatures of 25 °C, this very high density is on the verge of impacting growth
and survival, due to the increase of biomass present in the tanks.
As for densities in flow-through seawater systems, Sykes et al. (2003) suggested
the use of 120 cuttlefish m
−2
and minimum area of about 1,083 cm
2
(in 10 L raceway
tanks), when starting a new juvenile tank with individuals of approximately 5 g. According to these authors, these density and bottom area values are valid for animals
up to 25 g. Likewise, Domingues and Marquez (2010) studied the effects of both
density and bottom areas in open seawater systems (in concrete raceway tanks) and
obtained results that support the use of high-density and large bottom areas (33 cuttlefish m
−2
with an average weight of 9.5 g), registering similar feeding rates (≈ 10 %
body weight d
−1
) but different food conversions. In fact, mortality and growth were
similar between high- and low-density tanks using similar large bottom areas, which
indicate that the bottom area seems to be more important than the density itself.
Independently from the rearing seawater system, density must be decreased and
bottom areas increased while cuttlefish grows. It is suggested that, from 30 DAH to
10 g, the cited values of Sykes et al. (2003) should be used and from this weight and
to maturation (which is temperature dependable) the findings of Domingues and
Marquez (2010) should be considered.
If cuttlefish is reared in earthen ponds, special attention should be paid to the
density and bottom areas, considering the fast growth rates that the species display
and the inability to correctly observe what is happening within the ponds. If the
pond’s carrying capacity and biological limits are reached, cuttlefish mass mortality
and loss of total biomass produced will occur. This will be due to the inability to
clean the pond which will result in a spike in nitrogenous compounds and a drop in
dissolved oxygen. A common observation to detect that this limit is being reached
is to find eaten cuttlefish or cuttlebones in the pond as well as cuttlefish floating or
swimming in the pond’s surface.
11.6.3 Food
According to Warnke (1994), when cuttlefish are fed in a group, individuals hunt
three times faster than when isolated, more food is ingested and feeding hierarchies
are established.
Currently, growout of cuttlefish juveniles is performed with crustaceans as diet,
mainly the grass shrimp—P� varians (Sykes et al. 2006a). This is due to the easiness of collection (logistics) and results obtained with this diet (Sykes et al. 2006a).
Nonetheless, several different food items have been tested throughout the years,
either solely or as mixed diets. Domingues et al. (2001a, b) used the crab C� maenas;
Domingues et al. (2002, 2003b) and Sykes et al. (2006a) used live or frozen P�
A. V. Sykes et al.