Ecologists raise alarm over releases of mosquitokilling guppies

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Country Email Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe The little guppy Poecilia reticulata has developed a big reputation. For decades, the fish has been championed as a mosquito fighter and dumped into ponds and ditches to eat up the insect’s larvae. But among scientists, it has a different reputation—as an invasive species with a remarkable ability to reproduce and spread.Now, as health officials in regions facing mosquito-borne viruses like Zika consider expanding use of these predatory fish, ecologists are urging them to think twice. In a paper published online today in Biology Letters, a group of ecologists argues that the guppies—and other nonnative fish used for mosquito control—haven’t actually proven very effective mosquito fighters, but are known to pose ecological risks.   “It all sounds like it’s magical—you put the guppies in, they eat the mosquitoes, everything is fine,” says Rana El-Sabaawi, an ecologist at the University of Victoria in Canada and lead author on the new paper. “Our concern is that you have a potentially invasive species that is being introduced haphazardly.”center_img Click to view the privacy policy. Required fields are indicated by an asterisk (*) Larva-gobbling guppies may have been cutting-edge technology for U.K. colonialists aiming to rid the empire of mosquitoes at the turn of the century. But to El-Sabaawi, the strategy seems so old-fashioned that she was surprised to find out large-scale projects are underway. While “randomly Googling guppies,” she came across news reports from Pakistan that health officials had released thousands of the fish into the ponds and sewers of Karachi in 2013 to fight the transmission of dengue fever. And in a widely circulated news video documenting Zika control efforts in Brazil, El-Sabaawi was troubled by footage of a municipal government worker apparently “wandering around with a bunch of guppies and basically just introducing them in ditches.”That’s unnerving for El-Sabaawi and her co-authors because they know guppies are efficient invaders. They’re hearty and fertile, surviving in relatively polluted water, reproducing often, and giving birth to fast-growing, live young. A combination of accidental aquarium releases and mosquito control projects have spread the species from its native range in the Caribbean and the northern coast of South America to at least 69 countries, according to a 2011 survey.And several studies suggest that introduced guppies threaten biodiversity. Researchers in Hawaii found that guppies released in the 1920s drove down native fish populations, perhaps by competing with them for food and living space, and had likely changed the cycle of nutrients in water: Guppy-rich areas showed increased levels of dissolved nitrogen—from ammonium in fish urine and gill excretions—which, in turn, stimulated algae growth. (Another fish commonly used in mosquito control—Gambusia affinis—has also been associated with declines in native fish species.)The authors also question whether guppies are reliable mosquito slayers. Studies that back their effectiveness tend to have flaws, they say. Lab tests often starved the fish before exposing them to a diet of exclusively mosquito larvae. And studies in the wild have been small and poorly designed.That critique may be correct, but dismissing guppies as a control strategy is counterproductive, says John Hustedt, senior technical officer of the nonprofit Malaria Consortium in Phnom Penh, which has been releasing the fish into water storage jars in rural households to combat dengue fever and other mosquito-transmitted diseases. Hustedt hopes that a study his group has just completed will provide new evidence for the guppies’ value. Preliminary results showed that reductions in the number of adult mosquitoes were two times greater in households with guppies than in those without.“If someone comes out and says, ‘Actually it doesn’t work and it’s going to cause you a problem,’ that can decrease the chance that the government would be more open to trying [guppy release] on a large scale,” he says.As for ecological risks, guppies in isolated containers may be less likely to spread than those dumped into urban sewers and ditches. But Hustedt also questions the distinction between native and nonnative for a species that is already so ubiquitous. The guppies used in his project were found in a farm in a province outside Phnom Penh; their original source is unknown. “It seems to me that they’ve been here for quite a long time, and they’re already in the environment,” he says.Although the benefits and risks of guppy releases may be highly context-dependent, some researchers are simply taking a hard line. “The use of fish to control mosquito disease vectors should be abandoned by authorities,” says Valter Azevedo-Santos, an ichthyologist at São Paulo State University in Botucatu, Brazil, who co-authored a letter objecting to the strategy published in Science earlier this year. He believes resources would be better spent on other control measures: insecticides, sanitary measures such as eliminating standing water in homes, and even the experimental release of genetically engineered mosquitoes to spread a lethal gene. As health workers cast around for ways to combat Zika, he hopes this paper will give them pause. “This mismanagement must be abandoned, or new fish invasions will occur in the near future,” he says. “This is a special moment.”last_img

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