Mass Death of Carp School... Suspected Due to Oxygen Deficiency
Oxygen Levels in Water Dropped Due to Heatwave Causing Suffocation
Hundreds of carp were found dead in a mass die-off in the upper reaches of the Suyeong River in Busan. The local district offices are investigating the exact cause of the deaths.
On the 2nd, 'Yonhap News' reported that over the past weekend, hundreds of fish, including carp, were found floating dead on the water between Dongcheon Bridge and Sewol Bridge in the upper Suyeong River. It was reported that the dead fish decomposed, causing a strong foul odor.
The image shows carp from the Busan Suyeong River that died in a mass die-off being washed ashore. [Image source=YouTube capture]
The local district offices, including Haeundae-gu and Geumjeong-gu in Busan, have been working for about three days since the 31st of last month to collect the dead fish using nets and are seeking the exact cause of the mass die-off. Haeundae-gu reportedly collected samples at the site that morning and sent them to the Busan Institute of Health and Environment for analysis.
According to the institute's analysis, the mass death of fish is presumed to have occurred due to a shortage of water in some sections of the upper river. In particular, the continuous heatwave caused the water temperature to rise, resulting in shallower water depth and a rapid depletion of oxygen in the water, which also appears to have contributed to the deaths.
Generally, the dissolved oxygen concentration necessary for fish survival (referring to molecular oxygen dissolved in water such as rivers and seas) is above 4 ppm. However, the dissolved oxygen level in the upper Suyeong River was measured at 1 ppm. When dissolved oxygen falls below 2 ppm, fish essentially 'suffocate.'
This is not the first time that fish have died en masse and floated to the surface due to low dissolved oxygen levels. Earlier last month, about 300 sweetfish were found dead and floating on a section of the Sacheon River in Sacheon-si, Gyeongnam, shocking local residents.
Water quality tests at the Sacheon River at that time showed dissolved oxygen levels at 0.67 ppm, less than 1 ppm. The extreme heatwave, with temperatures hovering around 35 degrees Celsius, caused significant damage to the aquatic ecosystem.
Meanwhile, Haeundae-gu is conducting dredging work in the section where the carp died to secure additional river water. A district official told the media, "Some parts of the upper Suyeong River are currently exposing the riverbed," adding, "It appears that the carp died trapped in sections with low water while moving upstream and downstream."
© The Asia Business Daily(www.asiae.co.kr). All rights reserved.
