Tue, Jun 10, 2008 - Page 4 News List

Massive fish die-off last year caused by streptococcus bacteria, expert says


A leading expert said on Sunday that streptococcus bacteria caused a massive fish die-off at the end of last year around Green Island.

Over the course of two weeks in late December, residents found a great number of dead fish washed up on the shore.

At first residents believed that the fish had been illegally poisoned, or killed with electric shocks or dynamite by poachers, and some of them picked up the fish as food.

But as the number of dead fish increased, residents began to doubt the cause of death and the safety of eating the fish.

Researchers collected samples of the 26 species that were found and they were examined by the Penghu Marine Biology Research Center of the Taiwan Fisheries Research Institute.

The examinations excluded electrofishing or dynamiting as the cause of death.

Toxicology tests at other institutes showed that the fish were not poisoned, but Tsai Shin-shyong (蔡信雄), professor of the Department of Veterinary Medicine at National Pingtung University of Science and Technology, discovered that several samples were contaminated with streptococcus bacteria.

Streptococcus is generally found in closed aquaculture facilities where the quality of water is poor, especially during warm weather.

“The Green Island case might be the first in the world in which fish living in the open ocean have been contaminated with the bacteria collectively,” said Jeng Ming-shiou (鄭明修), deputy director of the Biodiversity Research Center at Academia Sinica and the expert responsible for the investigation.

Many additional aspects are also awaiting investigation, Jeng said, including how more than 1,000kg of large fish could become contaminated in the open ocean, where the impact of the microbe is generally diluted, and why the dead fish were all big ones that live 30m or more beneath the surface, while smaller fish active in the intertidal zone and close inshore were unharmed.

One of the possibilities was that fishing boats passing by the area dumped a large quantity of rotten fish that were then eaten by other fish, causing a large quantity of them to die in a short period of time.

Even though no more dead fish have been found since the end of last year, the investigation is still under way, Jeng said.

Jeng also said that streptococcus can be transmitted between fish and humans and that even though boiling kills the bacteria, it is better not to eat fish contaminated with the bacteria.

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