Jimbeizame: Whale Shark

There are so many sea animals on Earth, for example, fishes and mammal. Rhincodon typus is the biggest of fishes on earth. It is called a Whale shark in English.

It is a most body length of about 13.7m and width of about 1.5m. The figure is a spindle-shaped, flat head and the teeth are 300 to 350. The skin tissue is thick, and the thickness is about 10cm. Tail fin of the adult are usually crescents. However tail fin of the young does not stand out the lower part, and have the feature with large only upper part. The color is light yellow into white check in body, is white in stomach but without stomach, is ultra marine. Marking of the whale shark is seen personality each individual. It is so useful to individual recognition when we observe. The whale shark is very timid and a quiet-looking. It acts basically alone however rarely by the flock. Female of the whale sharks tend to stay in a specific sea area, on the other hand male of them wander a wide sea area.

Genus name is Rhincodon and species name is typus. Rhincodon typus was classified and described by Andrew Smith biologist British based on the specimen captured in the Table Bay in Cape Town in South Africa in April, 1828. It is guessed that Rhincodon typus was born 60 million years ago.

Whale sharks live in a subtropical, tropical, temperate zone in the surface sea area around the world and wander. They are seen also in the vicinity of the mouth of river, a lagoon, a coral reef and among bays.

The whale shark makes small ecosystem. Why can this be said? Whale sharks are filter feeding and eat plankton. Small fishes also are eating it. Medium fishes flock for eating small fishes. Large migratory fishes flock for eating medium fishes. Namely, the whale shark forms a small ecosystem by one individual. People thought that it was a lucky of good catch between fishermen. So, Japanese does not eat it. But it is said that the whale shark had been decreased enough to put on the Red List of endangered species. Because a developing people that suffer from a food shortage hunts excessively. Once it had been believed that the whale shark was oviparous. But it was turn out that it was viviparous in 1995. After the spawn hatches in the interior of the womb, the fry is given birth while having grown up from 40 to 60cm. It matures in about 30 years and lives at about age of 70. We do not know breeding of the whale shark much. But we know that their propagating power is low. And today it is said that the protection of the whale shark is important. Otherwise, it might be exterminated.

We can see the whale shark in Ashizuri Cape in Kochi. It wanders to Tosashimizu from June to September. Or always are able to see it at Kaiyukan in Osaka, Tyuraumi Aquarium in Okinawa and Iburi center in Tosasimizu. In Iburi center, the living thing to exhibit in Kaiyukan is collected, bred and the surveillance study of the surrounding ocean area is done.