His group had tried to bring in nets as evidence of poaching after police dismissed their concerns.
The event is observed with fireworks and with prayers in public gatherings and private homes.
Four are later released, though one is severely beaten while in custody.
The move comes as authorities restrict public gatherings in the run-up to the birthday of exiled Tibetan spiritual leader the Dalai Lama.
The move restricts the numbers living at Nyatso Zilkar monastery in protest-hit Yulshul prefecture.
Authorities ban the gathering of crowds who might proclaim their support for the exiled spiritual leader.
Their families have not yet been told what charges they face or where they are being held.
As demand and prices fall, traders turn the once sought-after dogs out to fend for themselves.
At least 10 are detained as police scatter protesters from land used by Tibetan villagers.
Relatives and friends celebrate their return to their home village in Sichuan's Ngaba prefecture.
But monasteries involved in protests are forced to take part in 'patriotic re-education' sessions.
Her self-immolation outside police offices in Gansu is the second such protest to occur in Tibetan areas of China this month.
They are taken into custody as authorities enforce curbs on sharing politically sensitive information.
Festival participants had paraded photos of exiled Tibetan spiritual and political leaders.
Authorities had harassed Tibetans suspected of planning birthday celebrations for the exiled Dalai Lama.
His burning brings the number of the fiery protests challenging China's rule in Tibetan areas to 140.
He had blocked police efforts to claim the remains of a monk who burned himself in a protest last year.