Using the SGPT Chamber for Field sampling and long-term captivity of
deep demersal fishes from tropical waters
Keiichi Sato, Atsushi Kaneko & Minoru Toda
Okinawa Churaumi Aquarium,
424 Ishikawa, Motobu-cho, Okinawa Prefecture, 905-0206, Japane-mail: k_satou@kaiyouhaku.or.jp

Abstract
Because of the strong influence of the warm Kuroshio Current from the south, the marine fauna off
Okinawa Island is characterized by beautiful tropical coral reefs and many colorful tropical fishes. For over3 decades, since the opening of the former Okinawa Expo Aquarium, now called the Churaumi Aquarium,
we have been collecting deep-sea fishes from the depths of 100-980m off Okinawa Island (25 27°N), andtrying to keep them alive for research and exhibit purposes. In general, it has been very difficult to achieve
long term success in keeping deep-sea demersal fishes, owing to the differences in pressure between thedeeper and surface waters, and in tropical waters, differences in temperature as well. A difference inpressure is a relatively simple problem to solve by using pressurized collecting and keeping tanks, but they
are prohibitively expensive. In this publication we introduce our successful and economically feasible
experiment in treating decompression disease by using our SGPT (Simple Gravity Pressure Treatment)
Chamber, which is pressurized by the forces of gravity produced by a tall narrow water column.

Introduction
Most deep-sea fishes inhabiting depths below 200 m have generally been considered unsuitable for
exhibit in aquariums worldwide, owing to the difficulties in providing them a habitat with adequate
pressure for survival. However, owing to their unique habitats and curious morphologies, many aquarists
desire to keep them alive for study and display. As Uiblein et al. (2010) noted, ex-situ observations cancontribute profoundly to behavioral research on deep-sea fishes.

Recent technological advances in

Keiichi Sato

deep-sea observation equipment, such as ROVs (Remotely Operated Vehicles) and high definition movie
cameras (Kubodera, 2010), for in-situ observations, are helping to introduce the mysteries of the deep-sea
world to scientists and TV viewers alike.
However, such in-situ observations on the deep-sea inhabitants are quite limited, because of theconstraints on viewing time and points of observation.
In order to fully study reproduction, feeding behavior and functional morphology of deep-sea fishes,
captive observations are of utmost importance. In recent years, several attempts have been made to keep137

collected deep-sea fishes alive. Koyama et al. (2002, 2005), and Koyama (2007) developed a hyperbaric
aquarium system with which they succeeded in capturing and keeping deep-sea zoarcid fishes from below
1000m. Drazan (2005) designed a hyperbaric trap-respirometer system to keep pressure at capture depth
and performed ex-situ physiological experiment on deep-sea grenadiers.

These recent experiments wereconducted using very small, quite complex, and extremely expensive high pressure tanks, and also requiredlarge research vessels and many technicians.
At the Okinawa Churaumi Aquarium, we have been trying various methods to keep deep-sea fishes
in captivity, and have succeeded in displaying live deep-sea fishes such as the ruby snapper (Eteliscorscans), snake mackerel (Thyrsitoides marleyi), threetooth puffer (Triodon macropterus) and several
deep-sea squaloids. Our samples of deep-sea fishes are taken mainly by using hook and reel, traps,long-lines and occasionally an ROV, but few species survived. In order to improve our results, wereconsidered our collecting and keeping methods.
According to our observations made on dead samples, the “bends” or “decompression sickness” isthe most significant factor prohibiting long-term keeping of deep-sea species of fish. Most of the fishes wecollect from the deep suffer decompression sickness, exhibiting expansion of the swimbladder, protrusionof the stomach from the mouth and eventual tissue necrosis by thrombosis. Visible symptoms, like anexpanded swimbladder, are possible to treat artificially and simply using surgical instruments. But othersymptoms such as bleeding at the fin tips and edges, invasion and infection of the necrotic tissue bybacteria etc., invariably result in death. For our research, we turned to studies of decompression sickness
and successful recompression attempts in humans, and decided to apply some of the same principles andsolutions to our design for a recompression facility for deep sea animals. Here we introduce our concept fora pressurized tank, the Simple Gravity Pressure Treatment (SGPT) Chamber, and report an example ofsuccessful treatment of decompression sickness of a deep-water catshark using the Chamber.

Materials and Methods
Chamber design
The design goals of our SGPT Chamber included: (1) a relatively low pressure and relatively large
volume tank, (2) an extremely silent and stable tank environment, (3) a simple and easy-to-operate design(4) safety features for power failures and operating mistakes. Our initial idea, an appropriately deep, cold,

maintenance, and the difficulties of quieting a noisy compressor, it would also be difficult for a diver toroutinely conduct research in those conditions. A second idea, a small closed tank with high narrow water

Keiichi Satohigh-pressure tank would have many disadvantages: besides the high costs of construction andcolumn (Fig. 1B), can produce the same pressure in the deep square tank (Fig. 1A), but would only beappropriate for brief periods of research, not long-term. Finally, we devised a special SGPT Chamber (Fig.
1C) which satisfied our design goals and which we report on here. It consists of a 300 L (Fig. 1D) holdingtank on the ground floor of Okinawa Churaumi Aquarium, with two polyvinyl chloride columns reaching
up to smaller tanks on the fourth floor (18 m above the ground), and two smaller satellite tanks each on the138

third (10m) and the second (5.5m) floors (Fig. 1E). It is a circulating system, each tank with inlet filters tohelp keep water quality clear, and with shut-off valves on each floor to create variable pressures in theholding tank. With this SGPT Chamber, we have achieved adequate pressures for successful recompressionof fishes caught in the deep-sea.

Keiichi SatoFig. 1. Diagrams of design ideas for deep-sea chambers all with 0.185 Mpa water pressure. (A) an 18.5m deepsquare water tank, simple but expensive and difficult to access. (B) a closed tank with a narrow watercolumn but not suitable for long-term research. (C) successful SGPT Chamber with system of D and Etanks. (D) 300L holding tank on the ground floor. (E) satellite tanks on the 2nd floor (left: 100L elevatedtank; right: 200L return tank).

139Collecting methods
The most useful methods for collecting live deep-sea fish for exhibition are by rod & reel and baited
traps (Fig. 2A), both methods commonly used by Okinawa's local deep-sea commercial fisheries. We
mainly corroborate with Mr. Yukinobu Taira, a local fisherman (“uminchu”) in Motobu-cho, Okinawa,chartering his 12m boat, the Kofuku-maru (Fig. 2B), to collect deep-sea fish around Okinawa. Our maintargets are deep-sea ruby snapper, sharks and snake mackerel. Caught fish are immediately moved into asmall holding tank filled with cold water on board the boat, and then transported to the Aquarium forrecompression treatment in the SGPT Chamber.

Research materials
An SGPT Chamber experiment was conducted using three individuals of a deep-water catshark

Keiichi SatoFig. 2. Sampling equipment and fishing boat. (A1-2) baited trap, (B) rod and reel fishing, (C) fishing boat
“Kofuku-maru”.

species known as Parmaturus pilosus, collected from 650 deep in the East China Sea off Okinawa Is.
Surface water temperature at collection (Oct. 22. 2006) was 26.8°C centigrade, and bottom temperature
was estimated to be 9°C. All the sharks were trap-collected and transferred by boat and truck to theAquarium in a tank filled with 10°C water. Duration of transport to the Aquarium was 3 hours. Conditionsof the sharks before the SGPT Chamber experiment are shown as follows. Of the two to be kept in the140

SGPT (Fig. 3), individual No. 1 (female, TL53cm)

showednormalbalanceandswimming behavior. Individual No. 2(female, TL53cm), swam out of balance in atipped position, likely because of a slightly
swollen liver, but nevertheless was suitableforexperimentation.

NO3(female,TL56cm), the control animal, was kept
without SGPT chamber treatment for theduration of the experiment in the 230 ton
Aquarium exhibit tank (3 m deep, 14°C).

Fig. 3. Two samples of Parmaturus pilosus under SGPT
Chamber experiment (right: individual No. 1; left:individual No. 2).

ResultsMaximum pressure (18.5m, 0.185Mpa) can be reached in the SGPT Chamber within about 5minutes, but a more gradual drop in pressure helps the fish equilibrate without problems. A sudden drop
seems to surprise the fish, causing them to ventilate rapidly.
After reaching 18.5 m / 0.185Mpa the pressure was held steady for ...and then slowly returned to normal
surface pressure over a 26-day period.

Individual No. 1
When pressure in the chamber reached the maximum (0.185Mpa), individual No. 1 established aconstant position 3 cm above the tank floor, swimming slowly round and round, and maintained that
position during the following 26 days of recompression. After recompression the individual was moved toa 7.5 t (cu. m) FRP tank (2m wide, 2.5m long, 1.5m deep) where it swam normally for 49 days, and thenbegan to eat on its own. Two years after being captured, it remains completely free of fin necrosis or othersymptoms of decompression sickness, and is still healthy.

Individual No. 2
Individual No. 2 never regained its balance during the same recompression treatment as describedfor No. 1. Although it remained free of fin necrosis after being moved to the FRP tank, it never was able toKeiichi Satofeed. Nevertheless, it lived for 238 days after treatment. Likely cause of death was starvation. However,examination of its liver revealed the oil droplets characteristic of decompression sickness in animals
collected from the deep sea and kept for a short time in an aquarium tank.

Individual No. 3
Although still seemingly normal on the fourth day after capture, on day 5 individual No. 3 began toshow the abnormal swimming behavior typically associated with decompression sickness. On day 9 it

141

swam weakly at the surface, its back projecting slightly above the water. By day 13 its caudal fin, anal fin,
two dorsal fins and nearby skin areas were becoming necrotic and it had difficulty swimming. It finallydied on day 28. Dissection after death revealed many oil droplets in the liver (Fig. 4), many more thanobserved in the recompressed No. 2 at its death.

Fig. 4. Necrotic liver of Individual No. 3 dissected after its death (left). Many oil droplets can be observed on
the surface of liver (right).

Discussion
Results indicate that recompression was completely successful for individual no. 1. Individual No.
2, although exhibiting out-of-balance swimming behavior, nevertheless lived for 238 days, dying ofstarvation not decompression sickness. Its decompression symptoms (oil droplets in the liver) at death weremuch less severe than in untreated individual No. 3. No. 3 showed the fin necrosis and liver damage typicalto captive animals suffering decompression sickness heretofore kept here and in aquariums around theworld. A world-first for successful recompression, our system is further attractive because it is both
inexpensive and simple. Although it creates a relatively low (18.5m) pressure, it is very effective. Ultimate
success of course is dependent on the species, individual differences, capture conditions, etc.
Although success is not always 100 percent, even animals collected from depths of 650m have beensuccessfully recompressed with our system. As we continually revise our recompression regime andimprove structural details of our system, we expect better and better results.

This SGPT Chamber is effective not only in alleviating normal symptoms of decompression
sickness, but has also shown great effectiveness in resolving other problems related to keeping bothKeiichi SatoAfterword

shallow-water and deep-sea animals, such as bulgy eyes, wounds and abnormal swim bladder metabolism.

Acknowledgements
We would like to express sincere thanks to Dr. Senzo Uchida, Director of Okinawa Churaumi
Aquarium for his direction, encouragement and financial support. Also, we thank all the staff of the Aquarium142

for their support in collecting materials and maintaining facilities for this research, and Dr. Katherine Muzik
for encouraging and proofreading the English manuscript. Finally, we appreciate Mr. Yukinobu Taira, for
conducting many deep-sea research cruises for the Aquarium research using his boat “Kofuku-maru”.

References
Drazen J. C., L. E. Bird and J. P. Barry. 2005. Development of a hyperbaric trap-respirometer for thecapture and maintenance of live deep-sea organisms. Limnol. Oceanogr.: Methods 3, 2005, 488498.
Koyama S., T. Miwa, M. Horii, Y. Ishikawa, K. Horikoshi and M. Aizawa. 2002. Pressure-stat aquarium
system designed for capturing and maintaining deep-sea organisms. Deep-Sea Research I, 49:2095-2012.
Koyama S., T. Nagahama, N. Ootsu, T. Takayama, M. Horii, S. Konishi, T. Miwa, Y. Ishikawa and M.
Aizawa. 2005. Survival of deep-sea shrimp (Alvinocaris sp.) during decompression and larvalhutching at atmospheric pressure. Marine Biotechnology, 7: 272-278.
Koyama, S. 2007. Cell biology of deep-sea multicelluar organisms. Cytotechnology, 55: 123-133.
Kubodera, T. 2008. Observations of mesopelagic large squids in the wild using recently developed
underwater visual equipment. Proceeding of an International Symposium, Into the Unknown,
Researching Mysterious Deep-sea Animals, 22-42.
Uiblein. F, F. Bordes, P. Lorance, J. G. Nielsen, D. Shale, M. J. Youngbluth and R. Wienerroither. 2008.
Behavior and habitat selection of deep-sea fishes: a methodological perspective. Proceeding of anInternational Symposium, Into the Unknown, Researching Mysterious Deep-sea Animals, 5-21.

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