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REARING TANK
Forsythe &Hanlon
WATER CONDITIONING TANK
Fig. 2. Basic closed marine culture system for rearing
OctopusJoubini. A water exchange pump. B return syphons. C crushed
oyster sheUfilter
bed. D air system. E air-lift. F auxiliary tank filter. G
protein skimmer. H heater. I ultraviolet light filter. J hatching
tank. K tray tank.L small rearing chambers in rack. M large rearing
chamber. J and K can be incorporated into the basic double tank
system. It is not usual for
aU rearing components to be in use simultaneously as shown.
REARING TANK WATER CONDITIONING TANK
Fig. 3. Diagrammatic representation of culture system. For key
to lettering see Fig. 2.
2 and 3). One tank served as the water-conditioningtank and the
other as the principal rearing tank. Awater exchange pump (A) and
return siphons (B)
provide continuous water movement between tanks at
a rate of 65 l/min. In the conditioning tank theseawater is
continuously subjected to biological and
mechanical filtration, physical adsorption and ultra-
violet-light disinfection. A 6 cm deep crushed oystershell
filter bed (C) is the principal site of biological
filtration. A low-pressure, high-volume air system (D)powers 4
air-lifts (E) which draw water through
the filter bed (C) at a rate of 15 l/min, allowing
nitrifying bacteria living in the oyster-shell bed to
oxidize toxic ammonia (NH3 ) to nitrite (N02 ), andfinally to
less toxic nitrate (N03). Mechanical filtration
of suspended particulate matter and detritus takes
place in the filter bed (C) and in side-mounted auxiliary
tank filters (F). Each of these auxiliary filters (E. G.Danner
Mfg Inc., 160 Oval Drive, Central Islip, New
York 11722, USA) is powered by a pump that draws
water at a rate of 65 l/min through 2 layers ofpolyester filter
fibre and a 4 cm layer of activated
carbon. The fibre reduces water turbidity and the level
of organic colloids. The carbon provides physical
adsorption of dissolved organics; half of it is changed
every 2-4 weeks, depending upon the animal load in
the system. A protein skimmer (G) removes surface-
active organics by foam fractionation. An 8 W, 2537nm
ultraviolet-light filter unit (1; Hawaiian Marine
Imports, 465 Town & Country Village, Houston,
Texas 77024, USA) provides ultraviolet-light disin-fection to
reduce populations of bacteria, algae and
protozoans that are often introduced with wild-caught
food organisms. The ultraviolet-light filter unit receives
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Breeding Octopus in the laboratory
water from an auxiliary tank filter pump, but because
of back pressure in the filter, flow rate is reduced from
65 to 45 l/min. A standard 150 W immersibleaquarium heater (H)
maintains constant water tem-
perature.
Natural and artificial seawater ('Instant Ocean';Aquarium
Systems Inc., 33208 Lakeland Boulevard,Eastlake, Ohio 44094, USA)
have been used in thissystem. Natural seawater is always passed
through a 1.urn diatomaceous earth filter prior to use, and
artificialseawater is made with deionized water to avoidtap-water
contaminants. Water quality is monitoredregularly to assess the
effectiveness of the condition-ing system. Temperature, salinity
and pH aremeasured several times weekly and estimates of nitriteand
nitrate concentrations are made once a week usingfield-kit chemical
tests (Hach Chemical Co., PO Box907, Ames, Iowa 50010, USA).
Periodic detailedwater chemistry tests are performed according to
themethods of Rand, Greenberg & Taras (1976) to
determine more precisely ammonia, nitrite and
nitrateconcentrations. When concentrations surpass therecommended
limits proposed by Spotte (1973), 25%
of the seawater is replaced. Deionized water is addedseveral
times a week to replenish that lost byevaporation.
The rearing tank may be used for stocking adult andjuvenile O.
joubini as well as rearing the hatchlings.
The bottom is covered with a 1 cm layer of crushedoyster shell
that serves only as a bottom substrate.Clay pots, polyvinyl
chloride (PVC) pipe fittings and
shells provide shelter or 'dens' for individual octopusesolder
than 120 days and greater than 3 g wet weight.
At this size the octopuses are large enough to use theitems
provided for dens, whereas smaller octopusesoften hide in the
oyster shell substrate, where it is
difficult to locate them. They are fed live crabs adlibitum, and
food debris and faeces are syphoned out
daily. Adult and juvenile octopuses should not bereleased in the
filter tank as they will burrow into and
under the filter bed, disrupting filtration.Several adults of
both sexes maintained in the same
rearing tank will mate readily. When eggs are laid, the
den containing the brooding female and eggs ismoved to the
hatching container (Fig. 21), a 10-15 I
rectangular clear-plastic aquarium (32 x 18 x 18 cm)placed in
the system (in Fig. 2 it is placed in a separate
water conditioning tank). A pump and return syphon
provide continuous water exchange and fine plastic
screening (approximately I mm2 mesh) is placed over
the syphon intakes to prevent hatchling escape.If provided with
moderate water circulation, eggs
separated from the mother will develop normally in the
hatching container. Females generally lay 50-150eggs;
development takes 30-40 days at 25C, withhatching occurring over 2
weeks (Boletzky &Boletzky, 1969; Opresko &Thomas,
1975).
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Fig. 4. Juvenile Octopus joubini, 7 weeks old, in a small
rearing
chamber. Showing mesh sides, crab remains (right) and
sheilfragments (beneath animal and left) provided as den material.
Line
represents 10 mm.
The hatching container is checked daily and the new
hatchlings removed either into the shallow clear-plastictray
tank (76 x 30 x 10 cm, Fig. 2K) for mass rearingor into individual
compartments (Fig. 2, Fig. 4). Thetray tank is connected to a
conditioning tank by apump and return syphons and has a water depth
of 4-5cm. Squares of plastic artificial grass inverted andfloated
in the tank provide shelter for the hatchlings,and the close
proximity of the grass to the tank bottom
allows individual octopuses easily to observe andcapture prey
(Hanlon, 1977). An excess of live food is
provided, and uneaten debris is removed daily. After3-4 months,
the young octopuses are large enough to
be transferred to the rearing tank.
Individual octopuses can be reared in separatechambers for any
part or all of their life cycle. Octopushatchlings and young
octopuses are isolated in smallrearing chambers made from
disposable 100 ml plasticbeakers (7 cm deep x 5 cm diameter) whose
wallshave been replaced with fine mesh screening to allowwater
circulation while preventing animal escape (Fig.
4). Groups of up to 40 chambers are supported in rigid
plastic racks at the water's surface in either the rearing
tank or water-conditioning tank. At a wet weight of2-3 g, young
octopuses are moved to larger rearing
chambers (Fig. 2M), plastic trays (28 x 17 x 13 em)
whose sides have been replaced with 3 mm2 mesh
plastic screen. The same screening is used to divide the
chamber, and an octopus is placed in each half. 4 of
these chambers can be supported in the rearing
orwater-conditioning tank. All chambers are supplied
with den material such as shells, and daily mainten-ance
involves only the syphoning out of uneaten foodremains from each
chamber and the addition of newfood animals.
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Breeding Octopus in the laboratory
have been successfully reared in open systems, such as
Hapalochlaena maculosa (Hoyle) from the Indo-west
Pacific (Tranter &Augustine, 1973), Octopus briareus
Robson, 1929 from the Caribbean (Wolterding, 1971;
Hanlon, 1977), O. maya Voss & Solis, 1967 from the
Gulf of Mexico (Van Heukelem, 1976), O.
bimaculoides Pickford &McConnaughey, 1949 from
California (R. A. Underhill, personal communication,
1973) and Eledone moschata (Lamarck, 1799) from
the Mediterranean (Boletzky, 1975). Holding capacity
for hatchlings and young juveniles of these species
should be about the same as those mentioned for
Octopus joubini. At 3-5 months of age, all except H.
maculosa surpass the adult size of O.joubini (15-35 g)
and grow on to 1-2 kg. 3 adults of this size could be
maintained adequately in the rearing tank, but a secure
top would be needed to prevent them from escaping. In
addition to octopuses, there are 13 species of sepioid
squids that are benthic and produce large eggs
(Boletzky, 1974) that might also be suitable for rearing
in this system. The system would have to be duplicated
References
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141
or otherwise enlarged to increase the holding capacity.
We conclude that rearing large-egged, benthic
octopods in closed systems is a feasible alternative in
situations where open systems are either unavailable
or undesirable. The use of this system, which is
convenient, reliable and repeatable, can facilitate the
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Acknowledgements
We thank Professor G. L. Voss, Dr D. V. Aldrich and
R. F. Hixon for critically reviewing the manuscript. D.
A. McConathy prepared Figs 2 a nd 4. J ohn W.
Forsythe thanks the Graduate College of Texas A &
M University for allowing the use of that part of the
material that is being incorporated in his M.S. thesis.
This work was supported in part by the Marine
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