Every year, greater numbers of Chinese sturgeon are found dead in the Yangtze River. Is industrialisation taking its toll on this ancient and protected species? Zhe Kan reports.
Before the 1980s, 3,500 Chinese sturgeon returned annually to the upper reaches of the Yangtze River to spawn. Today that figure is less than 500. Estimates put the breeding population at less than 1,000.
At Shanghai’s Sturgeon Rescue Centre, a Chinese sturgeon over three metres long is laid out on a table. It has been brought here for treatment. Covered in scars, it is still more fortunate than its kin, killed by fishing nets or ship propellers.
The fish was accidentally caught in a fisherman’s net on July 17. Its struggles left it with serious scrapes and grazes. Fortunately, specialists from the centre were soon on the scene, taking in the huge fish for expert treatment.
But this is no isolated case. This year there have been frequent reports of injury or death to Chinese sturgeons – contemporaries of the dinosaurs, and a protected species under Chinese law – in its most important habitat, the lower reaches and mouth of the Yangtze River.
A Chinese sturgeon known as “Shengsheng” was recently returned to the wild after treatment. Brought into the centre on a specially-designed stretcher, it was close to death. The base of its pectoral fin was bleeding heavily, there were serious injuries to its fins and tail and 27 wounds on its stomach, some gangrenous. Its breathing and signs of life were weak. But five months later, the specialists’ painstaking care and attention meant the fish was getting stronger every day.
Shengsheng was released on June 17. Its name means “life”, given to it by local primary school pupils in the hope that the species will survive. However, that very day, news came from Ningbo, in eastern China, that two more adult Chinese sturgeon had died. You cannot help but wonder if Shengsheng will live up to its name.
Incomplete statistics show that between last November and the present, 13 large Chinese sturgeon were wounded or killed along the Yangtze River. Only two survived. Since January, there have been eight cases of protected species meeting similar fates at the mouth of the river: five Chinese sturgeon, two black finless porpoises and one sperm whale. Most worrying is the size of the sturgeon that were wounded and killed; at an average of over three metres in length, and weighing 200 kilograms, they were all mature adults of at least 20 years, and at their most fertile. The loss of these fish has had a huge impact on the Chinese sturgeon’s chances of survival as a species.
But should this series of incidents be ascribed to natural causes? Or was it the work of humans?
The adult fish swim up the Yangtze River to breed, and on that 1,000-kilometre journey they constantly run a gauntlet of nets and ship propellers, enduring polluted water all the while. China’s Ministry of Agriculture once explicitly banned fishing on the river, but it proved too difficult to enforce. The small profit to be made is still enough motivation for many to spread their nets in the 576-square-kilometre sturgeon protection zone at the river mouth, posing a serious threat to the rare fish.
There are 106 major bridges on the Yangtze River, numerous dams and any number of water control gates, breaking the river into sections, which disrupts the upriver migration of wildlife and changes the river environment.
The draining of lake and riverside wetlands to create fields has also deprived many species of grounds to lay their eggs and raise their young. Migrating fish have far fewer places to stop and regain their energy. In May, an adult Chinese sturgeon was found sliced in two by a ship’s propeller. Astonishingly, an autopsy found that its stomach was empty. Experts believe that its feeding grounds had been destroyed, and it could only keep swimming until death from exhaustion or starvation – or in this case, a ship’s blade.
There is no solid scientific evidence explaining why so many large, endangered aquatic species are dying, but the experts each have their own hypotheses. Shen Xinqiang, from the East China Sea Fisheries Research Institute, says that the dredging of large channels for shipping has resulted in the loss of the routes the fish normally take. “Originally there were lots of channels to choose from, but now they have been combined into one, leaving no choice for the fish. They run aground, get lost and even die.”
His colleague Jia Hua thinks noise pollution is part of the problem. “Animals such as whales and dolphins use sounds waves to find and choose their way.” The noises from construction and machinery on the river banks can confuse them, leaving them disorientated.
The Yangtze River Tunnel Project is also giving experts cause for concern. A preliminary report on the expected impact of construction on the migration of the Chinese sturgeon found that piers used to build large bridges are slowing the river, putting the fish at greater risk of injury.
Perhaps those 13 dead and injured Chinese sturgeon are just a coincidence, and the scientists’ ideas are nothing more than speculation. But these events throw light on the importance of protecting rare aquatic life – and warn us, at least, of the Yangtze River’s ecological crisis.
Kan Zhe is a Shanghai-based reporter for chinadialogue.