Swaying its gray body, a three-meter long Chinese sturgeon
circles the pool quietly. "It feels much better than when it just
arrived here, since it can swim continuously," murmured Liu Jian,
staring at the fish in the pool.
Liu, deputy director of the Department of the Shanghai Yangtze
Estuarine Nature Reserve for Management of Chinese Sturgeon, has
been taking care of this sturgeon. Fishermen who caught it by
mistake near Hangzhou Bay sent him the huge fish.
This is the fourth adult sturgeon meeting with a mishap at the
Yangtze estuary in a mere six months. The first rashly headed into
an eel seedling net on January 18 and was rushed to Liu's
department for treatment. On May 2 and 26, two more bodies weighing
over 200 kilos were discovered in a row. One of them was cut into
two halves by screw propellers.
"There have been no accidental catches or deaths recorded
regarding adult Chinese sturgeons in this water area in the past
two decades," said Liu, expressing anxiety about recent high
accident rates.
The Chinese sturgeon, one of the oldest vertebrates in the
world, has existed for more than 200 million years. Adult Chinese
sturgeons usually migrate to Yangtze River from the sea during July
and August, and swim upstream to spawning grounds the following
October.
According to this timetable, adult Chinese sturgeons are usually
spotted between July and August or even from October to the
beginning of the next year. "It was rare for us to discover two
dead sturgeons in May," explained Liu.
"There have been 10 mishaps with adult Chinese sturgeons since
last November. Only one survived."
The death toll continues to rise. Two large Chinese sturgeons
were found dead in Xiangshan in June and another one in the Yellow
Sea water area near Nantong of Jiangsu Province in July.
While Liu is busy tending the injured fish, the plummeting
numbers of baby Chinese sturgeons has sounded another alarm.
The number of sturgeon hatchlings spotted at Chongming Base of
Yangtze Estuary Conservation Area dropped from 600 in 2006 to 15
this year.
In June 2005, 117 baby sturgeons were monitored, accounting for
78 percent of the annual total. Numbers dropped to 499 in June
2006, accounting for 83.2 percent of the annual total. But no
sturgeon fry have been spotted this June.
Although more than 100,000 artificially raised Chinese sturgeons
were released into the Yangtze River earlier this year, few of them
have been spotted at the conservation base. Meanwhile, the numbers
of other aquatic species fry: eel, saury (a sharp beaked fish) and
anchovy are also declining.
"We fear the declining population may be a bad omen for the
ecological environment of the Yangtze," said Liu.
This June, experts gathered to probe into the declining fish
population. Huge ships are the top killer, with six out of 14
casualties being killed by propellers.
The construction of the Gezhouba Dam on the river is also
believed to have decimated sturgeon numbers. The dam project, which
began in 1981, has cut the spawning area from 600 kilometers to
just seven kilometers. Wastewater directly discharged into spawning
area has made the hatching environment even worse.
?
Pollution has impacted and degenerated aquatic life in the wild. In
fact, the sperm survival times of wild Chinese sturgeon has dropped
from a range of 10 to 30 minutes to a range of three to five
minutes. Research also revealed a gender imbalance of 18 females to
one male sturgeon.
Nothing specific has caused the decline in Chinese sturgeon. "We
need to carry out extensive research, a three year project at
least, in order to reach an accurate conclusion," said Professor
Zhuang Ping, vice president of East China Sea Fisheries Research
Institute.
(China.org.cn by Huang Shan, August 6, 2007)
