Rising fees are making people in Shanghai's suburbs less willing to register their dogs, posing a challenge to the city's target of managing the pets, a discussion by the Shanghai Municipal People's Congress found on Wednesday.

A regulation that took effect last May cut the cost for registering dogs in the city to about 200 yuan ($32). For someone from the suburbs, however, that is an increase from the 100 yuan they used to pay.

Yao Zhirong, deputy director of the Shanghai Public Security Bureau, said there are now more unlicensed dogs in the suburbs.

According to statistics from the city's public security bureau, by the end of April there were more than 230,000 licensed dogs in Shanghai, an increase of 64 percent from 2010, thanks to the easy and cost-effective registration process.

The number of unlicensed dogs in Shanghai is not available, though Shanghai-based Labor Daily reported in April that there were 600,000 before the regulation was issued.

On the other hand, officials find it challenging to collect evidence and punish residents whose dogs pose a threat.

"It is hard to tell to what extent a dog has endangered public safety or disturbed other residents," Yao said, noting that dogs have usually calmed down by the time police arrive. Sometimes, police are locked outside by dog owners.

Also, although each licensed dog will receive a computer chip for identification (which costs 60 yuan), pet owners complain it is useless when they lose their dogs.

"I imagined the computer chip would help me track my dog if it gets lost. But have a look at all the notices of people looking for their dogs on micro blogs. Clearly the computer chip does not help at all," said Chen Shu, 24, a Shanghai resident, who raises a toy poodle.