A sudden rise in temperature yesterday in Kaohsiung City could be responsible for the deaths of 20,000 tonnes of fish in the Ai River (愛河), environmental officials said yesterday.
Kaohsiung City Government officials rushed to the Chungdu Bridge (中都橋) yesterday morning to collect water samples and remove dead fish floating in the river.
About 20,000 tonnes of fish were removed from a several-kilometer-long section of the river.
Officials said that the fish died due to a lack of oxygen in the water, adding that some mullet and milk fish were seen with their mouths open, struggling to breathe before they died.
Water samples taken at the scene registered a pH value of 7.1, which officials said falls within the normal range of 6 to 9.
Chen Meng-Hsien (
Officials said that both a high temperature and low tide could be responsible for the low oxygen-demand value.
According to the Central Weather Bureau, the city's maximum temperature yesterday was 29.7?C, higher than the 27.8?C maximum recorded on Tuesday.
No concentrations of pollution were discovered in the area, ruling out the possibility of the fish being poisoned, officials said.
"We will still examine the water samples collected to see if other hazardous chemicals exist," an environmental official surnamed Chen, who declined to be identified, told the Taipei Times.
Chen said that the sample would be examined for electrical conductivity, oxygen demand, pH value, cyanide, detergents, chromium, biological oxygen demand and chemical oxygen demand.
Environmental officials initially suspected that pollution from the harbor, 3km downstream, may have killed the fish, but Kaohsiung Harbor Bureau officials said fish near the site appeared normal.
Both the Harbor Bureau and city government officials stressed that efforts have been made to clean up the river, which was once notorious for its pollution.
The Ai River, where the Kaohsiung Lantern Festival was held last month, is one of the city's most scenic spots. Taxpayers have spent millions of dollars cleaning up the waterway.
The river had been heavily polluted since the 1960s. As early as 1968, the city government vowed to clean up the river by dredging it, but it failed due to overwhelming industrial pollution.
In the early 1970s, residents had complained about the dead, black river. The city government, however, did not complete a sewer project to prevent pollutants from entering the river until 1987.
One of Kaohsiung City Mayor Frank Hsieh's (謝長廷) goals is to have 25 percent of households connected to a sanitary sewer network by the end of this year. In 1998, only 6.5 percent of city households were connected to the network.