* This was originally posted on my old blog on August 1, 2010.
* 筆者の以前のブログに2010年8月1日付で投稿された記事の再掲です。
In my small aquarium, I keep some fish I caught with a rod and line in a nearby river. They are a species called "Carassius auratus (gibelio) langsdorfii", which is a close relative of Crucian carp, the wild form of the goldfish. This species is very commonly found all over Japan and well-known by the Japanese name of "Mabuna" or "Ginbuna."
However, something uncommon also bites from time to time in my local rivers. One of my biggest surprises was when a huge Channel catfish appeared from the water as I pulled the fishing line. Channel catfish originally had been distributed only in North America and never in Japan, until they were imported for the development of aquaculture for food. Yes, there have always been "Namazu" in Japan, which is usually translated into English as "Catfish". Namazu and Channel catfish are, however, members of different biological families just as cats and dogs. Actually, the word "Catfish" refers to a very diverse group of fish. Anyway, some of those imported channel catfish have gone back to the wild in Japan, and come to greet Japanese anglers. Should we say "Welcome to Japan!" to them?
The problem is that many species of Catfish including Namazu and Channel catfish are at the top of the food chain in almost any environment. Once they have been introduced to a new environment, they can easily threaten the native biosphere of the region. Of course, smaller animals can also be invasive as the ecosystem is nature's delicate balance, but imported carnivorous fish exert influence over the existing environment far more rapidly and clearly. Besides, Channel catfish is not the only example of this sort of case. Some kinds of trout, Bluegill sunfish and Black bass are also considered to be problematic in Japan. Many people think that extermination of invasive species might now be necessary. I personally do not think such a "just kill the strangers" take on the situation will work, but I cannot come up with any better idea. This is a really difficult issue.
We, as humans, are lucky in that sense. All of us in this world are members of the same species, Homo sapiens, and there is only one existing subspecies, Homo sapiens sapiens. We cannot be a stranger wherever we go in human society, which is almost everywhere on Earth.
