In 2007, the number of prince fish was about 25 million. Added to the bass, which was brought from the United States for sport fishing in the 1970s, the invaders represented 90% of the entire Lake Biwa fauna, which included 30 species of native fish. In 2005, the Shiga prefectural government spent R$ 6.64 million to remove 420 tons of invasive fish from the lake. Thanks to continued government-sponsored commercial fishing, the population has since halved, but bluegill perch and bass remain in the lake where traditional gillnets fail to catch smaller fish. In the past three years, eradication initiatives have cost the provincial government R$1.5 million annually. If fishing stops, the number of perch fish will rise again.
“the number of environments It appears to have decreased somewhat, and the population size in large bodies of water like Lake Biwa has decreased since 2005, but the distribution does not appear to have decreased,” Kawamura notes. “I have no hope.”
A solution may not be achieved
Finally, technology can offer a solution. Ongoing research led by Hiroyuki Okamoto, a fish geneticist, is focusing on “gene-induced inhibition in invasive populations” through the Crispr-Cas9 gene-editing tool. Okamoto’s team sequenced the bass genome and recently produced the first generation of male fish that can carry a female-specific sterile gene to the wild bass population, eliminating their ability to produce eggs. The program is in its sixth year in the laboratory.
While genetic sterilization appears to be working, Okamoto estimates that it would need to release an amount of modified fish equivalent to 7% of the invasive population to completely eliminate perch from Japan’s waterways, however, he believes genetic suppression can be successful.
The task may seem daunting, but “there is no more effective way to eliminate invasive species,” says Okamoto. “Commercial fishing takes time, needs a budget, and it’s very small and increasingly limited in Japan, which we’ve been doing for 20 years. Now that Crispr technology is available, it may be possible to solve this problem.”
However, he is not sure that the authorities will agree to release his sterile, gene-bearing perch into natural ecosystems. Because of his research, Okamoto reveals that he faces criticism and threats online from people who claim that organisms altered with Crispr should not be in nature.
“While we are aware of the genetic approaches that have been developed to stop chick reproduction, we remain wary of potential impacts on local ecosystems and their relationship to laws and regulations,” he wrote by email. Masaaki Uehara, Head of the Division for International Strategy at the Japanese Ministry of Environment.
Another major snag: Japan’s limited public support for chick management in general.
Okamoto compared the US Regional Coordinating Committee’s invasive carp budget of R$250 million for 2021 with Japan’s budget of R$88 million for all inland fisheries matters. “Given this discrepancy,” he comments, “I think the US population is more concerned about invasive fish.”
Saito agrees. “Ordinary people don’t care much about what’s going on in the water because it’s invisible to them.”
There is no simple solution
On the other side of the world, in Illinois, where Chicago is, where the Japanese perch originated, Kevin Irons encounters an invasive species of his own: the common carp. As director of the Harmful Aquatic Species Program at the Illinois Department of Natural Resources, he oversees mass fishing efforts to remove 750 tons of carp along the 530-kilometre Illinois River Basin each year.
Over the past decade, scholars in Japan and the United States have occasionally exchanged guidelines and methods for controlling their respective invaders. Irons teams collect water samples for DNA testing from scaly carp cells, a technology Pioneer created by Japanese geneticists to track the blue-gill sun chick. In 2012, Nakai Katsuki, a fish researcher at the Lake Biwa Museum, traveled to St. Paul, Minnesota, United States, to present developments in electric fishing and the development of artificial nests to the Carp Managers Conference. He remembers eating fried silver carp.
Despite advances in technology, there doesn’t seem to be a “simple solution right now to eliminate carp,” Irons admits.
But the technology developed by Okamoto’s team in Japan – genetic biocontrol, or target genes – is a source of great hope for some researchers at the US National Academy of Sciences.
“The fallout can be remarkable: for the first time, there may actually be a tool that has the potential to permanently eradicate a target species from the planet.” Three scholars wrote in the academic journal Proceedings of the National Academy of Sciences In 2015, shortly before Okamoto’s research began in practice.
“The question is no longer whether the invasive species can be controlled through target genes, but whether this method should be used,” they wrote.
But, according to the researchers, there are dilemmas and risks with this technology, such as unintended and accidental mutations present in this group for generations, or the global loss of a species if somehow modified individuals escape and return to their original habitat. It is also possible that another invader will fill the empty space in a short time.
As has been proven for decades, whether a Japanese prince takes home a tank as a souvenir or an American farmer imports common carp from eastern China, or in any environmental human intervention, goodwill is not always enough.
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