【明報專訊】Living Fossil of the Yangtze River

The Chinese sturgeon (中華鱘) is an iconic species living in the Yangtze River (長江). They first appeared 140 million years ago. Like sharks, they have a skeleton that consists of cartilage (軟骨) instead of bones. They have no scales but five rows of bone plates along the surface of their body. Of the 27 species of sturgeons and paddlefish (匙吻鱘科) in the world, the Chinese sturgeon is one of the largest and can grow up to five metres long. This is even longer than a seven-seater van!

Text & photos: Ocean Park Hong Kong

Migrating between the waters

Chinese sturgeons are migrating fish that live in both fresh water and the ocean during different stages of their lives. Adult Chinese sturgeons live in the ocean. From May to August, they swim more than 3,000 km upstream to spawn (產卵), which is the longest migration for sturgeons. The distance is approximately a round-trip from Hong Kong to Chengdu (成都), China. During their spawning period, they can live without food for more than one and a half year. A female Chinese sturgeon lays 400,000 eggs each season, but only a few thousand are hatched successfully and even fewer survive the early life stage. Baby sturgeons will stay in the river for a year, then they enter and remain in the ocean until they are sexually mature(性成熟) at around 15 years old. They migrate back to the river for breeding.

Challenging journey

As sturgeons are often caught by fishermen, their numbers continue to drop. Pesticides (殺蟲劑), chemicals and waste find their way into the river, degrading the habitat for Chinese sturgeons and other animals that live within. Although dams (水壩) can provide much needed energy, they may create barriers and alter the habitat for Chinese sturgeons as they migrate up and down the river.

Devoted scientists

Much effort is still required to improve the survival rate of Chinese sturgeons. Scientists play a vital role through their research. The National Aquatic Wildlife Conservation Association, the Yangtze River Fisheries Research Institute of the Chinese Academy of Fisheries Sciences, the Beijing Aquarium, Ocean Park and Ocean Park Conservation Foundation Hong Kong have joined hands to carry out research to answer the questions of "what should be done" and "how that can be done" to better protect this critically endangered species.

Yangtze — The longest river in China

The Yangtze River was the cradle (搖籃) of civilisation in China. Today, it remains integral to our lives. Millions of people depend on the river to survive and strive. It provides precious water for the community. Boats ply (航行) up and down the river to fish, to carry goods for trade, and to transport people from city to city. Apart from humans, the river keeps nurturing many unique animals and plants. It has also inspired artists for centuries with its natural beauty and vigour.

■Glossary

migrate (v) 遷移

alter (v) 改變

vital (adj) 不可或缺的

civilisation (n) 文明

[Smarties' Power English 第212期]