In the fall of 1960, when Japan’s Crown Prince Akihito embarked on a trip to the United States, he made a notable stop in Chicago, where he specifically requested to visit the Shedd Aquarium. At just 26 years old, the prince was already a committed ichthyologist and would later produce research on goby fish. During his stay, Mayor Richard J. Daley, an avid fisherman, welcomed him with a fitting present: 18 live bluegills, native sunfish from the Midwest, which were set to become Illinois’ state fish. This gesture was a symbol of goodwill a mere 15 years post-World War II\u2014a fish for a fish scientist, from one Great Lakes city to a nation famous for them.<\/p>\n
Out of the 18 original fish, fifteen bluegills made it across the Pacific alive. The project’s initial straightforwardness was striking: a handful of fish, an optimistic prince, and a plan.<\/p>\n
### The Scheme<\/p>\n
Rather than releasing the bluegills into a pond, Akihito entrusted them to Japan’s national Fisheries Agency with a defined goal: to breed, research, and possibly establish the American bluegill as a sustainable food and game fish in Japan, enhancing the nation’s protein resources during its post-war recovery. Over time, the bluegill earned the title “prince fish” in his tribute.<\/p>\n
For several years, the scheme progressed as anticipated. The agency successfully bred the initial stock, launching the first offspring into a lake near Ito City in Shizuoka Prefecture in 1966. Three years later, a commemorative structure was built along the shoreline. Further releases occurred across Japan’s freshwater ecosystems. Initially, the bluegill seemed innocuous. As Katsuki Nakai from the Lake Biwa Museum later pointed out, Japan had limited experience with invasive species at the time, and the bluegill did not seem menacing.<\/p>\n
However, the bluegill’s true potential revealed itself as time passed. It is a non-discriminative feeder, capable of consuming the eggs and fry of other fish. It reproduces abundantly and flourishes in the warm, murky waters often generated by modern development\u2014environments that pose challenges for Japan’s indigenous fish species. Once bluegills made it to Lake Biwa, the largest and oldest lake in the country, they encountered native species already weakened by another American introduction, the largemouth bass, and subsequently dominated the lake.<\/p>\n
### Tens of Millions of Princes<\/p>\n
By 2007, Lake Biwa was estimated to host around 25 million bluegills. The species expanded in ponds, moats, and rivers throughout the nation, all originating from the 15 fish from Chicago. Genetic research confirmed this lineage, as a team led by Kouichi Kawamura at Mie University analyzed various Japanese populations against U.S. source stocks, tracing the invasion back to the gifted bluegills and matching their DNA to the Mississippi near Guttenberg, Iowa, where the Shedd Aquarium had originally gathered the fish. A population small enough to fit in a bucket had managed to colonize an entire archipelago, and despite the anticipated inbreeding, their growth persisted relentlessly.<\/p>\n
The ecological destruction spread throughout Japan’s crucial waters. In Lake Biwa, bluegills played a role in the decline of native fish such as the crucian carp, vital for the region’s traditional funazushi delicacy, and drove other indigenous species to the brink of extinction. As a result, Shiga Prefecture imposed a bounty on bluegills, prohibited restocking with severe penalties, and by 2005, the national Invasive Alien Species Act listed the “prince fish” as undesirable. Symbolically, even the imperial moat in Tokyo, close to Akihito’s palace, required partial draining to remove the unwelcome descendants of his gift.<\/p>\n
### It Pains My Heart<\/p>\n
Emperors seldom confess their mistakes in public. However, in November 2007, Emperor Akihito did precisely that at a national fisheries gathering on Lake Biwa’s shore. Reflecting on the introduction of bluegills from America fifty years earlier, he expressed sorrow that the fish, which was intended as a food source, had inflicted significant ecological damage. This acknowledgment was interpreted as a rare display of remorse from the throne. Katsuki Nakai’s response was understanding, noting that in 1960, the notion of invasive species was barely recognized.<\/p>\n
This narrative stands out among invasion accounts, serving as a clear natural experiment. There were no accidental introductions or ambiguous sources. The species was intentionally selected by one mayor, transported by one prince, bred by one agency, honored with a monument, and ultimately faced by an emperor who shared in the outcome. From a mere fifteen fish, the population swelled to millions, with the man who initiated it witnessing the unforeseen consequences unfold before him.<\/p>\n","protected":false},"excerpt":{"rendered":"
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