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Efforts to eradicate rainbow trout from Ecuadorian waters will begin later this year

Ecuador’s environmental ministry is preparing a plan to eliminate rainbow trout from the country’s high-elevation lakes and rivers and hopes to implement it later this year.

Rainbow trout were introduced to Ecuador in the 1920s.

The eradication program was prompted by the work of biologists at the University Indoamérica in Quito that concluded that the rainbow trout is one of the most destructive invasive species in Ecuador. The biologists first approached the government in 2016 about the problem and have been consulting on methods to rid the country’s water systems of the trout ever since.

Introduced from North America to Ecuador in the 1920s, the rainbow trout is common today in the rivers and lakes of the country’s sierra region, most prominently in Cajas National Park west of Cuenca. It has also spawned a small industry of commercial production and the fish is widely available in stores and roadside stands.

The problem, according to Juan Manuel Guaya, an evolutionary biologist at Indoamérica, is that trout are wreaking havoc on other aquatic species and are responsible for killing off some. “They threaten native species in highland water ecosystems and the effect has been devastating in some systems,” he says. “Trout are not only a predator but they transmit deadly pathogens to other fish and amphibians.”

Guaya’s research shows that the presence of trout have almost eliminated several species of frogs in the Andes and upper Amazon basin, including the glass frog (Nymphargus grandisonae) and the Amazon bullanguero sapito (Engystomops petersi).

The trout have changed the behavior of tadpoles, Guaya says. “They have adapted to swim faster to avoid the trout and many die due to stress from chemical signals emitted by the trout.” He added that frogs that develop from the tadpoles often have birth defects. The study also shows that diseases transmitted by trout cause death rates as high as 80% in amphibian embryos.

Guayas and his team are working with the Ecuador Ministry of Agriculture, Livestock and Fisheries on ways to control the trout population. “It may not be possible to eliminate rainbow trout entirely from the ecosystem,” he says. “They are now in 125 countries of the world and they are hard to get rid of. The government will focus on national parks since it has control in these areas. With the means we have, it should be easier to eradicate them from high-altitude lakes and then we will move on to rivers and streams,” he said.

Guayas said that Cajas National Park near Cuenca will be the first target of the eradication program. He said he is working with biologists in Colorado, in the U.S., to identify natural pathogens as well as genetic methods to eliminate trout. The plan will be carried out by aerial spraying, he says.

A spokesman for the environmental ministry said that discussions will begin soon with commercial fisheries that grow rainbow trout in an effort to reduce the financial impact on affected growers.

30 thoughts on “Efforts to eradicate rainbow trout from Ecuadorian waters will begin later this year

  1. In the states its a battle to have clean enough water to support native trout, here they want to eradicate them, go figure. Hate to say but this over a few frogs. Its a losing cause anyway is my guess, there are a lot of people with a lot of money that would love to come chase those trout, one look at the Orvis website is convincing enough.

  2. Excellent move…rainbow trout may be great for anglers but they are an introduced species here. As with many invasive species, they compete with native species for spawning habitat and food. Because there are so many farmed rainbow trout, they also have the potential to introduce diseases (not the least of which is whirling disease) to native fish species. Educated anglers know these things.

    1. No one arguing the dangers of invasive species. These trout are embedded now. Spending money to rid them now is wasteful. Too late. 270 lakes in the Cajas plus streams

          1. I’ve noticed you have done that several times before. It must be some sort of Freudian slip. Have it checked out.

  3. How can the poor tadpoles tell the difference between the chemicals emitted by trout, and the chemicals being dumped by humans? I’ve redden past the car wash in Cuenca, while dumping the run off into the Tomebamba….the odor is SO strong, it made me cough! Maybe in high altitude lakes, they can control the tests…..but in the rivers, running through Cuenca….it’s just plain too nasty.

  4. Invasive species? They have been here 100 years, according to the article. By now, they are as native as anything else. And they are a heck of a lot better eating than frogs…

  5. Is eradicating the trout easier than stopping the pollution (dumping of chemicals) into the river system. Enforce the dumping laws first !!!

  6. Govt “do-gooders” in the USA have a history of creating problems or compounding existing problems.
    I have very little faith in Govt interventions. Shouldnt the citizens of Ecuador have a say regarding eliminating a major food source?

  7. Don’t they have anything else to do? Trout is served at restaurants and it is rather good to eat. Who really cares about the frogs and the tadpols. And rainbow trout exists in many countries, all over the Earth. Leave them alone! They should be more concerned about the poor habits of the local people that by throwing all kinds of garbage in streams and rivers contribute to destroy the habitats of humans and animals. Concentrate on plastic, please…..!!!

  8. And how many speciues are you going to kill with spraying? Nice how not a single word on what kind of toxic chemicals they will spray, more hubris by scientists and what do the people who live here in these mts think?? Scientists so-called.

  9. Is there a point at which an invasive species becomes native?
    The short answer is ‘no’. A longer answer is as follows: Species naturally change their ranges over time, usually just by small amounts – invading areas contiguous with where they lived before – but sometimes by long-distance dispersal even across ocean gaps. Monkeys reached South America from Africa, presumably by rafting on trees washed out to sea, for example. Over 30 million years [please check that number!] they have radiated into many new species, adapted to their new environment, and their competitors (sloths, marsupials etc.) and predators. Clearly they are now native, and so will the descendants of grey squirrels in Europe be after 30 million years. So ‘yes’, at some point between 0 and 30 million years. Where you draw the line is pretty arbitrary. Is the dingo native in Australia after 4000 [again check!) year? No, but it is on its way: genetically and behaviorally distinct from the dogs that came with people, but still the same species.
    – R. T. Corlett
    Xishuangbanna Tropical Botanical Garden

    By Definition, an invasive species is a plant or an animal or even a pathogen that is not native to the ecosystem under consideration. Another thing about invasive species is that their introduction is likely to cause harm to the native species. Therefore an invasive species cant be a native species.
    – Rashid C.A Kawawa
    Masinde Muliro University of Science and Technology

  10. “The plan will be carried out by aerial spraying,” Doesn’t sound too healthy to me. I don’t understand why the frogs need to survive and not the trout, which provide food for people… I must be missing something here.

  11. Another wild scheme to spend tax money on…if they want to erradicate them so bad, let people fish for free!!! You’d soon solve the problem that way….and less contamination. If they are thinking of dropping airborne chemicals to kills them off, WHAT ABOUT THE REST OF THE WILDLIFE THAT LIVES ON THE EDGES OF THOSE STREAMS AND PONDS????? somebody isn’t thinking it thru….

  12. I find this interesting. How will it be done, total fish fill followed by restocking using only native species? What about the farms along the river streams that raise trout, I assume a few trout get out of the farm and would repopulate the area anyway. How long will it take, cost and chance of success. Knowing the aforementioned is needed to say if it is a bad or good idea.

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