Safety first

It takes four to seven hours to transport one bucket of fish. Oxygen is injected into the water, and the condition of the fish is monitored. Photos of the fish are taken by underwater cameras to tally numbers and identify species. These are uploaded to computers in real time.

The system was designed to avoid people touching or netting the fish, which can harm their chances of survival. "No fish has been found dead when the release gate is opened," Liu added.

Because it is automated, the system requires only two maintenance workers and four workers on the ship to complete the assisted migration. Operating costs are thus minimized and efficiency is enhanced.

"We didn't expect the system to function so well from the start, but seeing the massive number of fish of different shapes and colors jump into water, we felt happy," Liu said. "We even saw hundreds of ospreys gather there."

Challenges include stabilizing water currents at fish collection points. Water flows around a station can change drastically in the electrical regulation process, especially during peak output, said Zhou Binghao, senior engineer of the program from China Water Northeastern Investigation, Design and Research.

Precise monitoring of water levels is needed to judge when to open and close the sluices, he said. Equipment must be kept in top condition to make the system work, so unfixed items are stored in a warehouse during the winter.

"The success of this program will serve as an example for other large hydropower stations," Zhou said, adding that in the future, efforts will be made to optimize the system to attract more fish and reduce transport time.

"The emphasis on ecology shows that awareness of environmental protection is rising as national economic strength grows," he said.

Li Xintong, 21, who lives in Fengman district, Jilin, said: "I heard about the fish ladder and I think it's a great thing. There are more fish in the Songhua River with different variety. The surrounding environment also became better. I'm glad to see our ecological environment improving."