A Reddit user recently sought advice on how to handle a rash of Japanese stiltgrass on their grandparents’ property.
“In my grandparents’ yard in West Virginia, there’s a pretty large patch of Japanese stiltgrass that’s been spreading pretty bad,” they wrote on r/invasivespecies.
“It’s been there for a few years now. I’m visiting for the summer, and I’d like to help them get rid of it, but I’m not sure of the best way to go about it,” they added.
Photo Credit: Reddit
Photo Credit: Reddit
One major challenge they faced was big: Weeding can actually encourage it to spread due to disturbed soil.
Japanese stiltgrass has been described by experts at the Alabama Cooperative Extension System as “one of the most damaging invasive plant species in the United States.” Like most invasive species, Japanese stiltgrass has a tendency to reproduce quickly, unencumbered by the natural checks and balances with which it evolved.
When a species is moved out of its native environment, it is often positioned to overrun its new home and establish a monopoly on vital resources. This can include food, water, and habitat.
As a result, native species are displaced, leading to a decline in biodiversity and the vital ecosystem services that people depend on. One study suggested that invasive species are responsible for hundreds of billions of dollars of economic losses each year.
The original poster didn’t want to use chemicals that might harm native deertongue plants in the area. Despite those hurdles, it didn’t take long for them to begin the removal process.
Fellow Redditors empathized with the amount of hard work required to eradicate Japanese stiltgrass in the comments.
“We spend about 3 weeks pulling in late summer; I mean we really go at it. We prioritize hills where fresh seeds would travel downhill with rain,” said one community member. “We also prioritize deer trails to cut down on seeds traveling with them. Keep up the good fight.”
“Consider seeding the no-mow native lawngrass Nimblewill (Muhlenbergia schreberi) over the entire affected area!” the gardener replied.
“[Japanese stiltgrass], being an annual, has less and less open soil available to it as time passes. With a little careful pulling from you, in the worst patches, you will help the Nimblewill win faster (but it will win),” the user explained.
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Guillermo Otta Parum has been fishing in the Bolivian Amazon his whole life, for more than 50 years.
At first, Guillermo was catching native fish, such as the various kinds of catfish which inhabit the river.
But then a giant freshwater fish arrived, known locally as paiche or Arapaima gigas, to give it its scientific name.
“I thought this creature was a water snake, that it would attack everything, that eating it would be bad for you, that it might be poisonous,” he recalls.
In fact, it is one of the biggest freshwater fishes in the world, growing up to 4m in length and weighing 200kg (440lb) or more.
Guillermo Otta Parum has been a fisherman for 50 years
It is estimated that every year, the paiche spreads another 40km deeper into the rivers of the Amazon basin.
Federico Moreno, director of the Beni Autonomous University’s Centre for Aquatic Resources Research, says its size and appetite make it a serious threat to native fish stocks.
“It is a territorial fish, it takes over a body of water and scares off the native species. [That] is one of the serious problems. The other species flee from the predator and enter other bodies of water much further away, more remote and difficult to access.”
No one really knows the exact year that the paiche first appeared in Bolivia.
It is generally believed its arrival was the result of a breach of a paiche fish farm in Peru, where the fish are native. From there, they spread into Bolivia’s rivers.
Biologist Fernando Carvajal has spent years studying the Paiche
Fernando Carvajal is a biologist and expert on the paiche. He says they are a ravenous species.
“During the first years of life, the paiche grows at the rate of 10kg a year. That means the paiche is eating a lot of fish.”
Unlike other predatory fish like piranha, it only has small, not particularly sharp teeth.
But its lack of impressive teeth does not stop it from eating piranha and a host of other fish, along with plants, molluscs and birds, all of which it hoovers up like a giant vacuum cleaner.
It also frightens off any fish which tries to eat the paiche’s young.
Fernando Carvajal says there is no firm data about the impact of the paiche, but he says that anecdotally, fishermen are reporting that the numbers of some native species are dwindling.
“In the next one or two decades, the paiche is going to spread to all the potential areas where this species can live,” he warns.
“We know that around the world, most invasive cases are bad for nature. Invasive species are considered the second-biggest reason for the loss of biodiversity after habitat destruction.”
However, for local fishermen, the arrival of the paiche has been a boon. Having been initially afraid of it, it did not take long for fishermen to realize its potential, says Guillermo Otta Parum.
Paiche fishing boat on the Yata River in the Bolivian Amazon
“When I brought the first fish, I would give the customers small pieces as a gift for them to try so they would get a taste for it.”
Some fishermen even pretended it was a type of catfish to overcome people’s suspicions about eating such a huge specimen.
Now paiche are eaten across Bolivia.
Edson Suzano runs a paiche-processing plant in Riberalta, a town in north-east Bolivia close to the Brazilian border.
Edson Suzano (left) says the paiche is affordable
“We sell it everywhere – supermarkets, markets. There are different cuts, so it is affordable. We buy and process around 30,000kg per month,” he says.
The challenge for the fishermen is trying to find the paiche in the huge expanse of the Amazon.
The fish has a lung-like organ and has to come up for air regularly to breathe and so likes calmer water. It prefers to live in lakes and lagoons, but migrates when it feels it is in danger.
The paiche migrates when it feels it is in danger
Most of the fish Edson Silvano processes used to arrive by boat.
Now the fishermen travel to ever more remote areas to catch the paiche and have to transfer from boats to canoes, on journeys of up to two weeks. This is putting them in conflict with indigenous communities.
These communities have been given land titles to many of the remote lagoons where paiche are now to be found and have themselves started fishing for and selling the fish.
Paiche being prepared for sale at Riberalta’s fish market
Now commercial fishermen have to obtain special licences to work in these areas. But fishermen like Guillermo Otta Parum say that even when they have the correct paperwork, they are often turned away.
The indigenous communities argue that they are only trying to protect the resources which the Bolivian government has recognised they have a right to control.
Juan Carlos Ortiz Chavez is a paiche fisherman who belongs to the Alto Ivon Tco Chacobo indigenous community:
Juan Carlos Ortiz Chávez belongs to the Alto Ivon Tco Chacobo indigenous community.
He says that in the past, indigenous people were scared of commercial fishermen. “But this new generation of young people has changed, because we have made our rules so that people can’t come and take from us any more,” he explains.
Scientists such as Federico Moreno hope that fishing generally, whoever is doing it, will keep paiche numbers in check.
“Keep hunting them, keep fishing for them all the time and that could keep a balance between the different species.”
