Back to the fish story we told you about in today's Geo Quiz.

It all begins with a US-Japanese exchange nearly 50 years ago...as The World's David Leveille explains:

This fish story goes back to 1960 when the Japanese emperor, at that time crown prince Akihito paid a royal visit to the United States. He was treated to a White House dinner, an excursion to Disneyland, and because he's a marine biologist, he asked to visit Chicago's Aquarium.

"I knew about Crown Prince Akihito's visit to Shedd Aquarium in October, 1960 from our board of trustees' minutes which I read."

Karen Furnweger is (editor and content manager) keeper of the archives at Chicago's Shedd Aquarium. She says at the time, the aquarium was honored to host the crown prince:

"While he was here, he asked for a collection of native Illinois Great Lakes' fishes for the Imperial Palace pond and Mayor Richard J. Daley arranged for him to receive 80 fishes, they were provided by the Fish and Wildlife Service, and Shedd's involvement was to pack the fishes for flight, so we packed them up."

The fishes, bluegills among them, were presented as a gift from the people of Chicago.

"Evidently all the fishes arrived in Japan in excellent condition which unfortunately now has repercussions."

Back in those days food was scarce in parts of Japan and the bluegill was prized as a delicious catch. Akihito passed the fish along to Japan's Institute of Fisheries in the hope of cultivating them as food. They were released and bred in Lake Biwa, Japan's largest lake and incidentally the answer to our Geo Quiz.

Emperor Akihito

In the 1990's the bluegill population exploded. By 2002, there were an estimated 50 million of these fish in Japan's lakes and waterways.

They even infested the royal moat surrounding the Imperial Palace. As a result Japan has had to spend millions to exterminate the species to keep it from crowding out Japan's native fishes. Bluegills in Japan are an invasive species akin to the Zebra Mussel in the Great Lakes or the Asian Carp in the Mississippi.

This week the Emperor, expressed "heartfelt distress" for the whole matter. {Akihito in Japanese} Akihito spoke at a national marine biology convention ( annual National Convention for the Development of an Abundantly Productive Sea). He urged scientists and environmentalists to "keep a close eye on the creatures of Lake Biwa" so that native breeds won't become extinct.

Back in Chicago the Bluegill has fared much better. It's the official state fish.

Joe Ferencak of (impoundment program manager) Illinois' Department of Natural Resources Division of Fisheries oversees the management of Illinois lakes.

"The bluegill is found throughout Illinois in combination with Largemouth Bass and catfish, they are fairly easy to catch using insects, crickets, or bits of night crawler, small worms, so it's a great way to introduce kids to fishing."

But that advice falls on deaf ears in Japan where the Bluegill is now only good for fertilizer and chicken feed, and where the Emperor has urged wildlife experts to be more vigilant in keeping foreign species of plants and animals out.