Okinawa Ocean Expo Aquarium

Expo '75 was held in Okinawa, Japan, at the Ocean Expo Park, where an aquarium centered on marine life was displayed. In 1976, the Okinawa Ocean Expo Aquarium was established as a national park on the site of the venue.^[9] The former aquarium was designed by Fumihiko Maki. ^[10]

The Okinawa Ocean Expo Aquarium and the Okichan Theater started operations with the facilities used at the Expo. At that time, the largest main tank in the aquarium had a water volume of 1,100,000 litres (291,000 US gal), which was the largest in the world.^[11][12]

The Okinawa Ocean Expo Aquarium is one of the first public aquariums in the world that breeds large sharks and rays such as whale sharks and manta rays.^[11][12]

The captivity of manta ray dates back to at least 1978. The first individual was captured by fishermen, entangled in a net, and threaded through a rope into a spiracle, which severely damaged it. Despite its injuries, the aquarium managed to transport it alive to a tank, where it recognized the tank walls, swam to avoid them, and ultimately survived for 4 days.^[13][14]

The first attempt of keeping whale sharks in an aquarium was in 1980.^[9][15] Most were obtained from incidental catches in coastal nets set by fishers (none after 2009), but two were strandings. Several of these were already weak from capture or stranding and some were released,^[15] but initial survival rates were low.^[16] After the initial difficulties in maintaining the species had been resolved, some have survived long-term in captivity. The record for a whale shark in captivity is an individual that, as of 2021, has lived for more than 26 years in the Okinawa Churaumi Aquarium from Okinawa Ocean Expo Aquarium.^[17]

At a symposium held in Baltimore in 1985, the Okinawa Ocean Expo Aquarium was rated to have the most advanced breeding technology in the world for long-term rearing.^[11] In 1988, the aquarium won the first Koga Award from JAZA in Japan for breeding two generations of whitetip reef sharks.^[18]

From the collapse of the bubble economy, as the park lost incoming tourists, it was believed that a new aquarium would help revive the area and celebrate Okinawa's marine tradition. In addition, since the facility was built for a short-term expo, it deteriorated significantly, and a plan to build a new aquarium was proposed.^[4]

Opening of Okinawa Churaumi Aquarium

The Okinawa Ocean Expo Aquarium was closed in August 2002 due to facility deterioration, and the Okinawa Churaumi Aquarium was opened on 1 November 2002, with a new facility designed by Yukifusa Kokuba(1939–2016) is an architect from Okinawa.

The number of visitors in the year before the old aquarium closed was about 430,000, but the number of visitors in the year after the opening of the new building increased to 2.75 million.^[20] The number of visitors has continued to increase, with the number of visitors reaching 3,784,132 in 2017 and the cumulative number of visitors reaching 50 million in 2019.^[5]

The aquarium's facilities also included a dolphin studio and a sea nursery, but due to deterioration of the concrete and other factors, they have been out of use since the end of January 2007 and have all been removed.^[9]

Since 2007, Okinawa Churaumi Aquarium has been conducting an annual learning program for elementary schools in Motobu-cho and Nago city, "Environmental Learning from Sea Turtles," which is an educational activity about ecology and the natural environment through the breeding of sea turtles.^[21]

In 2012, a general rest area (Churaumi Plaza) opened.^[9] Since 2018, the aquarium has opened its offshore research facility to the public by OKINAWA SAKANA CAMPANY.^[22]

In 2020, the number of tourists in Okinawa Prefecture decreased significantly due to the COVID-19 pandemic.^[23] The aquarium supervised the Sony aquarium [ja], which was held at the Ginza Sony Building every summer until 2019 before the COVID-19 disaster. The fish once displayed at the Sony Aquarium were brought in from the Okinawa Churaumi Aquarium.^[24][25]

In 2023, he was awarded the Koga Award, the highest prize in Japan for rare species breeding, for his research activities in sea turtle breeding on the IUCN Red List and Appendix I of CITES, for his ecological and conservation research through captive breeding of sea turtles and breeding over two generations.^[26]

The Okinawa Churashima Foundation has been certified under the "Okinawa Prefecture CO2 Absorption Certification System" for the management of a total of 380 Garcinia subelliptica, Dypsis lutescens, and other trees around the aquarium during the 2023 CO2 absorption certification period.^[27]

The Kuroshio Sea

The main tank, called the Kuroshio Sea, is 35 metres (115 ft) long, 27 metres (89 ft) wide and 10 metres (33 ft) deep.^[31] It holds 7,500,000 litres (1,981,000 US gal) of water and features an acrylic glass panel measuring 8.2 by 22.5 metres (27 by 74 ft) with a thickness of 60 centimetres (2 ft),^[32] the largest such panel in the world when the aquarium was opened.^[3][33]

Whale sharks and manta rays are kept alongside many other fish species in the main tank.^[3] Four species of mobula are kept at the aquarium, including the manta ray.^[34]

Since 2015, the aquarium has also had a reef manta ray with a black body.^[35] Since 2018 they also keep giant oceanic manta ray.^[36] The world's first birth of a manta ray in captivity was at the aquarium in 2007. This species and the giant oceanic manta ray were only recognized as separate species in 2009; they were both classified as Manta birostris until then.^[37][38][39] By the time the mother died in 2013, seven puppies were born and four survived.^{[40][41][42][43]} There is a record that the male reef manta ray, which lived in captivity in 1992, lived for about 23 years.^[44]

Okinawa Churaumi is trying to breed whale sharks in captivity, which has never been achieved by an aquarium. Their oldest male reached sexual maturity around 2012 and began to show an interest in females in 2014. The exhibited until 2021 female was on display^[45] (another is maintained away from the public) is 8 m (26 ft) long.^[46] There were three whale sharks, but they have been moved to a separate tank to make room for breeding.^[47] In 2021, a 13-year-old female whale shark that had been in captivity in the Kuroshio Sea tank was transferred to a medical treatment tank in the sea due to poor health, and later died. The cause of death is thought to be feeding difficulties from skeletal abnormalities in the jaw and a twisted pylorus.^[48][45]

The Coral Sea

In the Coral Sea tank, 450 colonies of reef-building corals of about 80 species are bred and exhibited.^[49] The tank has a capacity of 300,000 litres (79,000 US gal), no roof, a structure that allows strong sunlight to enter, and a constant supply of fresh seawater to enable large-scale breeding of coral.

The Coral Sea tank is made to emulate the coral reefs in Motobu.^[49] The aquarium has confirmed simultaneous coral spawning for 22 consecutive years.^[50] In 2021, the Okinawa Churaumi Aquarium was temporarily closed due to the COVID-19 pandemic, but it was confirmed that Acropora microphthalma gave spawned in the daytime for the first time.^[51]

In the same zone as the Coral Sea tank is another tank called The Sea of Tropical fish tank. This tank has a capacity of 700,000 litres (185,000 US gal) liters of water and In addition to coral houses 180 species of fish, including large fish that are difficult to breed in the Coral Sea tank, which specializes in coral propagation.^[52] In this tank, the shallow rocky areas to the depths of the caves in the coral reefs of Okinawa are reproduced in a single tank.^[52]

In 2024, the tropical fish tank was the first in the world to exhibit Pinjalo lewisi, a fish that had never been kept in captivity, alive.^[53]

The Shark Research Lab

Sharks such as bull sharks, tiger sharks, silvertip sharks, and silky sharks are bred in the shark research lab tank. Some bull sharks kept in aquariums have lived for more than 42 years.^[17] The lab also displays many skeletal and fetal specimens of sharks.^[54]

In 2016, the aquarium showed an attempt to raise an adult great white shark. The great white shark exhibit was successful, but it died three days later, leading to criticism from animal rights groups.^[55] In 2019, aquariums captured a pregnant tiger shark and succeeded in giving birth in a shark research lab tank.^[56]

The Deep Sea

Most of the deep-sea organisms at the Okinawa Churaumi Aquarium were collected from depths greater than 300 m (980 ft) around Okinawa. Because many deep-sea species are undiscovered, rare species, including new species and species recorded for the first time, are often exhibited, and the actual deep-sea environment observed by the ROV is reproduced.^[57][58]

In 2017, ROV surveys were conducted in the waters near Okinawa at a depth of around 200 m (660 ft). A total of 20 species of deep-sea invertebrates were collected and nine species, including Holothuria dura, were displayed.^[59]

In the same year, also discovered areas with high densities of Lyrocteis imperatoris and Saracrinus nobilis, which are considered difficult to capture and keep in captivity. Especially for Lyrocteis imperatoris, succeeded in keeping them for more than one year, and bred individuals were kept and The breeding individuals were also exhibited.^[59]

The aquarium has succeeded for the first time in captive breeding of salamander sharks, which live at depths of around 600 m (2,000 ft) in the seas around Japan. They are oviparous, and the eggs were echogenically examined regularly for 18 months until they hatched.^[60] The aquarium also saw sharks give birth in 2014 and 2017.^[61]

Shark and ray breeding and research

Many researchers are located at the Okinawa Churashima Foundation Research Center, including Keiichi Sato (佐藤圭一), a principal researcher who specializes in shark and ray research and has authored several papers through his work at the Okinawa Churaumi Aquarium.^[80]

The Aquarium collects blood from wild whale sharks, measures the total length and circumference of the body, collects tissues for DNA analysis and chemical analysis, and observes behavior in the natural sea using electronic labels^[18] to obtain important information on the breeding habits and ecology of whale sharks. It also conducts tests for future breeding, such as monitoring the behavior of whale sharks during breeding and the concentration of hormones in the blood obtained by blood sampling.^[18]

The Aquarium's Research Institute has been working on the development of an "artificial uterus device for sharks" with the aim of ex situ conservation of rare sharks, and from 2021 to 2022 raised the fetuses of a deep-sea shark, Etmopterus molleri, using an artificial uterus device. Also succeeded in stable growth after "birth" and reported the results in an international journal.^[81]

Humpback Whale Research and Studies

The aquarium is investigating many humpback whales with local people and domestic and foreign researchers.^[82] In a joint study with the Philippines in 2021, it was revealed that 43.48% of the humpback whales around the Philippines were the same as the individuals confirmed in Okinawa and were moving between the two waters,^[83] revealing the migration route of humpback whales between Okinawa and the Philippines from the previously unknown Russia feeding ground.^[83]　

Also, a paper on the diurnal variation of humpback whale sounds in Okinawa was published in the journal Marine Mammal Science and received an award as one of the most cited papers in the journal in 2021-2022.^[84]

Discovery of new species

As a research institute, the public aquarium contributes to the discovery of new species of marine life. New species discovered in the past include Eumunida balteipes,^[85] Hexagonaloides bathyalis,^[86] and Synactinernus churaumi, a new species of sea anemone that has been studied for over 15 years.^[87]

Based on specimens in the aquarium's collection, the species was described as a new species in 2020 as "Plectranthias ryukyuensis" with the cooperation of Kagoshima University and others.^[88]

A new species of starfish Churaumiastra hoshi was discovered during a ROV survey in March 2021. Will report the new starfish species in collaboration with the Smithsonian Institution and the National Museum of Nature and Science, and have since begun exhibiting the new species.^[89]