350
J. Nabhitabhata
About 15,000 t (12 % of the total cephalopod catch) of octopus including Amphioctopus aegina are caught annually from Thai waters, the Gulf of Thailand and
the southern Andaman Sea (Supongpan 1995; Department of Fisheries 2012). The
major fishing methods involve several types of trawlers. Considering the homing
behaviour of this octopus, the most recently emerging gear in the Southeast Asian
region is the artisanal octopus trap derived from the Japanese octopus pots. Fishermen have substituted the original clay pots with local and lower cost materials, e.g.
gastropod shell, Cymbiola nobilis, concrete blocks, soft-drink bottles. Srikum and
Somchanakit (2011) reported that one fisherman owns 200–5,000 trap shells and
obtains a monthly average yield of 10 g per trap shell from the Gulf of Thailand.
The octopus fishing grounds vary in their locations but mostly, it is between 200 and
8,000 m from the shoreline, at a water depth of 2–18 m. The octopus trap is an appropriate gear for fishing in view of natural resource conservation for two reasons.
The first one is that the fishing period is 7–20 days per month, so the remaining
period of every month is reserved for natural stock recruitment. The second reason is
that most of the Amphioctopus aegina captured by traps are mature, of a total length
of 190–220 mm (Srikum and Somchanakit 2011), and therefore only the full-grown
stock is exploited.
18.2 State of the Art
As mentioned in previous chapters, the culture of octopus species that involve
planktonic hatchlings, like Amphioctopus aegina, is more difficult compared to
those that have benthic hatchlings. The outstanding problem is that these hatchlings
are plankton feeders and require live food organisms of a specific size range and
characteristics (Hanlon 1987; Boyle and Rodhouse 2005; Villanueva and Norman
2008). The subsequent transitional period before their complete settlement also involves a change to a new characteristic type and size of food organisms.
The marbled octopus, Amphioctopus aegina, has a moderate size and as an adult
presents a benthic habit. This is an advantage since it is possible to provide culture
conditions on a small scale. Broodstock can be collected from the wild and consecutive generations can spawn in captivity, which can ensure a continuous supply of
hatchlings for aquaculture. Small-scale facilities can be used for culture of the species through its entire life cycle. Amphioctopus aegina is the second benthic octopus
species with planktonic hatchlings, after Octopus vulgaris (Iglesias et al. 2004), that
can also be cultured throughout its entire life cycle. Such success in aquaculture requires the problems associated with the rearing of the planktonic hatchlings and also
to overcome the transitional phase prior to settlement. To resolve these difficulties,
hatchlings are commonly fed for the first month with several types of wild-collected
live zooplanktonic species. After complete settlement, they can be then trained to
accept dead feed or inert diets. The daily growth rate is 1.9 % in length and 6.4 % in
weight throughout the culture period of 140 days (Promboon et al. 2011). A growing
demand for using this octopus as a neurophysiologic experimental model as well as
an ornamental animal cannot be overlooked.
J. Nabhitabhata
About 15,000 t (12 % of the total cephalopod catch) of octopus including Amphioctopus aegina are caught annually from Thai waters, the Gulf of Thailand and
the southern Andaman Sea (Supongpan 1995; Department of Fisheries 2012). The
major fishing methods involve several types of trawlers. Considering the homing
behaviour of this octopus, the most recently emerging gear in the Southeast Asian
region is the artisanal octopus trap derived from the Japanese octopus pots. Fishermen have substituted the original clay pots with local and lower cost materials, e.g.
gastropod shell, Cymbiola nobilis, concrete blocks, soft-drink bottles. Srikum and
Somchanakit (2011) reported that one fisherman owns 200–5,000 trap shells and
obtains a monthly average yield of 10 g per trap shell from the Gulf of Thailand.
The octopus fishing grounds vary in their locations but mostly, it is between 200 and
8,000 m from the shoreline, at a water depth of 2–18 m. The octopus trap is an appropriate gear for fishing in view of natural resource conservation for two reasons.
The first one is that the fishing period is 7–20 days per month, so the remaining
period of every month is reserved for natural stock recruitment. The second reason is
that most of the Amphioctopus aegina captured by traps are mature, of a total length
of 190–220 mm (Srikum and Somchanakit 2011), and therefore only the full-grown
stock is exploited.
18.2 State of the Art
As mentioned in previous chapters, the culture of octopus species that involve
planktonic hatchlings, like Amphioctopus aegina, is more difficult compared to
those that have benthic hatchlings. The outstanding problem is that these hatchlings
are plankton feeders and require live food organisms of a specific size range and
characteristics (Hanlon 1987; Boyle and Rodhouse 2005; Villanueva and Norman
2008). The subsequent transitional period before their complete settlement also involves a change to a new characteristic type and size of food organisms.
The marbled octopus, Amphioctopus aegina, has a moderate size and as an adult
presents a benthic habit. This is an advantage since it is possible to provide culture
conditions on a small scale. Broodstock can be collected from the wild and consecutive generations can spawn in captivity, which can ensure a continuous supply of
hatchlings for aquaculture. Small-scale facilities can be used for culture of the species through its entire life cycle. Amphioctopus aegina is the second benthic octopus
species with planktonic hatchlings, after Octopus vulgaris (Iglesias et al. 2004), that
can also be cultured throughout its entire life cycle. Such success in aquaculture requires the problems associated with the rearing of the planktonic hatchlings and also
to overcome the transitional phase prior to settlement. To resolve these difficulties,
hatchlings are commonly fed for the first month with several types of wild-collected
live zooplanktonic species. After complete settlement, they can be then trained to
accept dead feed or inert diets. The daily growth rate is 1.9 % in length and 6.4 % in
weight throughout the culture period of 140 days (Promboon et al. 2011). A growing
demand for using this octopus as a neurophysiologic experimental model as well as
an ornamental animal cannot be overlooked.