Chenrup, 67, a nomad, said the prospect of being reborn as a fly or a dog could not be dismissed. “We have the same feelings as the fish,” said Chenrup, a vegetarian who spends eight hours a day digging in the mud. “It is our duty to liberate them from pain and suffering.”

From early morning until dusk, the soul-savers work to extract creatures that have become stranded as the river, which is fed by snow-draped mountains, recedes in summer. The shrimp, about the size of a fingernail clipping, are almost impossible to see in the sunbaked muck and only make themselves known by writhing faintly. After collecting them in buckets or paper cups, the diggers set them free into the river.

From the thousands of multicolor prayer flags that flutter across barren mountainsides to the monasteries that fleck even the most remote valleys, religious devotion suffuses every aspect of life on the Tibetan Plateau. Although many people here consume meat — and tending livestock sustains most rural families — it is not uncommon to see yaks or goats adorned with colorful strands of yarn, an indication that their lives have been spared.

Across the plateau, the practice of life liberation supports a growing mini-industry. Since 2008, the Kilung Monastery in Sichuan Province has saved hundreds of yaks, sheep and goats through a program financed largely by believers overseas. For $1,000 a yak and $100 a goat, participants can buy an animal headed to the slaughterhouse. A nomadic family will also set aside an animal in their herd and dedicate it to providing wool ($165) or milk ($35). The monastery accepts online payments, including Visa and MasterCard.

Local monks acknowledge that the practice has a negligible impact on the number of animals destined for slaughter, but they say it serves to remind people about the sanctity of life and can also produce concrete benefits for adherents.

In an essay to his followers, Chatral Rinpoche, a 101-year-old Tibetan religious figure who is said to have saved more than a million animals in his lifetime, said mercy release could lead to better harvests and healthier, longer lives for practitioners. “No greater crime is there than taking life away, and no conditioned virtue brings greater merit than the act of saving beings and ransoming their lives,” he wrote in a widely circulated essay. “Therefore, should you wish for happiness and good, exert yourself in this, the most supreme of paths.”