Young brownbanded bamboo sharks. The aquarium succeeded in breeding of this shark for the first time in Japan. They inhabit the coast of southern Japan, Philippine, Indonesia and Australia. An adult grow up to over about 40in (1m) long.

Now the aquarium has 53 species of sharks which are from domestic sea and foreign. The number is outstanding not only in Japan but even in the world. The aquarium tries to understand the ecology of each sharks and succeed in breeding. Despite of dangerous image of sharks such as great white sharks and tiger sharks, most of sharks are docile.

They are also popular among people, but few things are known of their breeding and growth. So the aquarium goes into partnership with universities and other research organization to study sharks.

Since almost all shark population in the world is declining, that is the reason why the aquarium collects sharks from both domestic and foreign. Rare one is from Nagasaki, southern Japan and from South Africa. The aquarium is trying to save those unique sharks.

“Even within same species each of them has personality, one is rough, another is timid and the other is gentle. You have to observe them every day to see it though.”
said aquarist of Oarai aquarium, Kazuhiro Shibagaki.

It is necessary for staffs to know every single shark character, because there is power balance within one species. Staffs should understand the relation between one shark and another to rear sharks, otherwise weak shark may lose their appetite because of stress and have some trouble of its immune system. In that case staff transfer weak one to another tank to recover.

Mainly there are two types of sharks, one is bottom dweller and another is active swimmer. For bottom one staffs sometimes change design of rocks in the tank to keep healthy environment. For swimmer such as hammerhead which is very sensitive to new environment staffs swim along with it when it is transferred. The other fish with hammerhead in same tank are also carefully chosen.

Principally sharks have two ways of breeding, laying eggs or giving birth babies. In captivity it is very difficult for those deliver babies to breed, because they usually bear just two babies at a time. However the aquarium has succeeded in breeding of some rare species of sharks. Naturally the condition of females is the most important during the mating season, but sometimes a female is bitten by a male and gets injured. The shark coupling is very rough. In natural environment females can escape from violent males, but in the tank they have nowhere to go. Female and male should be separated just in time. The diets of sharks are also important, because females need nutritious food to make eggs during their pregnancy. Moreover some sharks mate once a year but another do all seasons. Staff also should consider congeniality between a female and a male. One of the most difficult species to breed is sand tiger shark.

Shibagaki has been taking care of sand tigers for 12 years and having consideration for them. “Just few sand tigers in captivity succeeded in breeding. They mate once a year and unlike other species female fight back while they are mating. So both female and male always have some scars on their body during the season. They do not eat much or even vomit when they are not in good shape. We must keep eye on those signs.” said Shibagaki.

Sand Tigers are also over hunted around the world and almost terminated in some region. Unfortunately they were taken their lives because their appearance. By-catch is still one of the serious threats they are facing.

Aquarium staff dives in the tank and introduce marine animals to visitor. Sometimes a shark rush into school of sardine, but it is not successful most of the time.

Together with some species of shark a sea turtle and several fishes such as rays, sardines and moray eel swim in the tank. Some sharks approach the other fish with curiosity, but they do not cause any troubles. On the other hand some sharks are very shy with the other fish. It is impossible to recreate natural environment, but visitor could imagine their habitat environment.

“Sharks are surely popular among visitor, but we also want to show the environment that sharks live in to our visitor. I think through that experience people may feel closer to sea around us” said Shibagaki.