Something's fishy

The Guangzhou Water Bureau announced on October 10 that mosquitofish, capable of consuming more than 200 larvae a day, would be released in a bid to control the dengue fever outbreak, Xinhua reported on October 16.

Some experts have warned that the fish, a universally acknowledged invasive species, may create some unexpected ecological consequences.

Previously released in Hong Kong and Taiwan, the fish decimated the habitats of the White Cloud Mountain Minnow native to those regions, the Guangzhou Daily reported.

But Guangzhou water authorities explained that mosquitofish have lived in Guangdong waters for decades, assuring that releasing limited numbers will not have a negative impact on the environment.

Over 20 million "native species fish" have recently been introduced to more than 2 million square meters of lakes and reservoirs, Wu Renchu, head of Guangzhou Patriotic Health Campaign Committee Office, told the Global Times. He said the number includes not only mosquitofish, but other mosquito-consuming species.

Nevertheless, Yi Zusheng, an associate professor at the School of Life Sciences at Guangzhou University, argued that "although introduced to China as early as the 1930s, mosquitofish is still an exotic and invasive species that poses a threat to the survival of native aquatic life."

Mosquitofish, which breed rapidly, compete for habitat with native species like White Cloud Mountain Minnow and Chinese rice fish, Yi told the Global Times, which are becoming an increasingly rare sight.

Since mosquitofish already populate the Pearl River Delta, releasing more is unlikely to help curb the spread of dengue fever, Yi said.

The water bureau argued that the release of about 5,000 mosquitofish in city parks in 2006 yielded positive results.

Wu Renchu, however, admitted there was no follow-up conducted after the introduction. Likewise, no projections for the possible impact on the ecology have been calculated this time around.

"In fact, the dace, a native species, is also a great mosquito eater," an unnamed official with Guangzhou's Bureau of Ocean and Fisheries told the Guangzhou Daily.