A recent research team in Tianjin has completed a fish census of the main stream of the Haihe River, identifying over 100 species and creating a population map of the river's aquatic life.

The Haihe River, one of China's seven major river systems, flows through eight provincial-level administrative regions and municipalities, including Tianjin, Beijing, and Hebei. It serves vital roles in shipping, flood control, and water supply, while also nurturing rich aquatic biodiversity.

To study the diversity of fish in the main stream of the Haihe River, the Wildlife Resource Conservation Research Team from Tianjin Normal University conducted a year-long survey. They established 12 sampling points along the river to complete the fish census.

Professor Zhao Dapeng, the team leader, stated: "In the ecosystem, fish play a crucial role. They are key components of the aquatic food chain and serve irreplaceable functions in maintaining ecological balance and promoting biodiversity. Moreover, fish are highly sensitive to changes in their living environment, making them important indicators for assessing the water's ecological quality."

Traditional monitoring methods often rely on fishing.

"Fishing sampling can impact fish populations and even disrupt the ecological balance in local waters," said Zhao. "To minimize environmental interference, we introduced internationally advanced environmental DNA technology, achieving a zero-interference objective."

E-DNA technology involves collecting DNA-containing materials, such as fish scales and mucus, from water samples. Specific DNA sequences are then analyzed to identify fish species.

Wu Hong, a team member, said, "We used data to unveil the mysteries of the Haihe River's underwater world."

This census has, for the first time, clearly presented a survival map of fish in the Haihe. A total of 103 fish species were discovered, belonging to 17 orders, 29 families, and 64 genera, showcasing a vibrant community and the robust ecological vitality of the river's main stream.