A group of workers have been heading to the Qinghe River in Tiantongyuan, northern Beijing to try and catch underwater worms, which they can sell as fish food. They call themselves “water cleaners,” and mostly work in couples.

In the one-meter-deep river, over a hundred men use what looks like very long string bags to catch the worms. They then pass the full bags to their wives waiting nearby, who then pick the worms out.

At about 2 o’clock in the afternoon, the catchers sell the worms to buyers who come over to the river. One couple can catch a daily average of about fifty or sixty kilos of worms - worth three or four hundred yuan.

According to the catchers, these worms are mosquito larvae - which can be processed into fish food - and this kind of business began a few decades ago.

One worm catcher called Zhang Laosan, who has been working in this business for over 20 years, said that he is part of a group of worm catchers in the district of Fangshan, and there is another one in the district of Tongzhou - a total of over 300 catchers in the city.

Beijing Water Authority said this kind of fishing does not harm the river’s ecosystem, but the authorities are trying to stop the catchers for their own safety. Environmental activist Zhang Junfeng has researched the impact of this business and said that it actually helps to clean the river. Some have suggested that the authorities could help the catchers move to a cleaner and safer location.

This photo shows “water cleaners” trying to catch worms in the one-meter-deep Qinghe River, under Beiyuan Bridge in Beiyuan Road, Beijing, July 19, 2014. [Photo/CFP]