Exotic fish and mammals from abroad, some imported as pets and later abandoned, are threatening the lives of animals that have existed in Japan for centuries.

The country is overflowing with freshwater black bass and small-mouth bass and mammals such as mongooses and raccoons, all species originating from abroad. They are of particular concern on the islands of Okinawa and Amami Oshima in Kagoshima Prefecture, but they can even be seen in the moat of the Imperial Palace in Tokyo.

Since it has become apparent they are threatening Japan’s ecology, the Environment Agency set up a study group in August to discuss ways to halt their breeding.

Experts say it is hard to foresee whether officials can work out any effective means to stem the tide because, for instance, there are many ways to bring foreign species into Japan.

“Looking at the long term, it has become conventional wisdom among scientists in the world that transported species are the biggest cause of extinction of life forms,” said Kazumi Hosoya, a professor of agriculture at Kinki University.

Foreign fish and other animals adversely affect confined areas such as lakes and islands. More than 300 species endemic to Lake Victoria in Africa are said to have been annihilated by one kind of foreign fish.

Mongooses, originally brought to Japan to exterminate poisonous “habu” snakes, are a serious threat to goats on the Ogasawara Islands and snakes on the islands of Okinawa and Amami Oshima. Weasels are also creating a serious problem on Miyake Island.

Okinawa and Amami Oshima are home to many rare species, including those indigenous to the islands. They have formed their own unique ecosystem. However, once mongooses were introduced, they quickly multiplied in the absence of a natural enemy.

Similarly, flesh-eating freshwater black bass and bluegill, originally from North America, are seriously endangering Japanese freshwater fish that have been in existence since long before the imported fish arrived.

There has been a bass fishing boom in Japan, and people have set them free illegally in rivers. Also, there are signs of the spread of fertile small-mouth bass.

In a survey conducted in fiscal 1984 by the Environment Agency, foreign-origin fish caught in the moat of the Imperial Palace amounted to less than 20 percent of the total seized. In fiscal 1999, bluegill accounted for almost 90 percent of the catch. The amount of Japanese “motsugo” carp caught accounted for only 8 percent of the total.

Some people say the pet boom is also worsening the problem of species coming to Japan. Raccoons, popular in animated television programs, are thriving wild in Hokkaido and ruining wild birds’ habitats.

Red-eared turtles, ferrets and hedgehogs, originally imported as pets, have been seen in various parts of the country.

Masaoki Murakami, an assistant at Kyoto University who is well-versed in the introduction of pets, said Japan is far behind other nations on animal import restrictions. He said Australia has a law that severely restricts people from bringing in animals from abroad.

The Environment Agency plans to spend the next two years working out a basic policy on the matter of transported animals and giving guidance to relevant people.

The agency will move into high gear in the eradication of mongooses on Amami Oshima. For the first time, it will also incorporate into its wildlife protection project a phrase spelling out the need to eradicate introduced species through positive efforts.

Officials, however, said the agency will not make any decision for legislative measures to restrict the import of animals until the study group it established in August completes its task.

Researchers and environmental protection organizations are strongly calling for such a law. But the officials said it is difficult to enforce import restrictions because the range of transported species is wide and officials concerned are spread over a number of state offices.

Government sources said that for the present, directives without any legal restrictive power is the only means available to cope with the influx of foreign animals.

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