Amir Khadir, the sole member of Quebec solidaire in the legislature, stayed calm during his detention but said he was surprised at the manner in which protesters were held by police.
He was among dozens of people rounded up in Quebec City during a nighttime march against tuition fee increases and a new provincial law putting limits on demonstrations.
Marie-Eve Painchaud, a Quebec City police spokeswoman, said the arrests were carried out under the provincial highway code because the demonstrators were blocking traffic.
"They went in a different direction than expected," she said of the march, which was mainly peaceful.
Khadir, who has attended several of the demonstrations, stood quietly as riot-equipped police waited to escort him to a nearby city bus where people were being detained. The politician, who was dressed in a jacket and tie, then sat calmly on the bus with his hands cuffed behind his back.
Christian Dubois, Khadir's media spokesman, was able to speak to Khadir while he was detained on the bus, waiting to receive a ticket with his fine before being released.
"He said he was shocked that people were handcuffed," Dubois said. "He said people didn't need to be handcuffed for a traffic violation."
Dubois said Khadir had just left the legislature on his bicycle when he heard the demonstrators banging pots and pans and decided to join them. He was scooped up shortly afterward.
The police had declared the march illegal moments before and said they issued several warnings to disperse.
Khadir isn't the only member of his family to be arrested during the student demonstrations. His daughter was nabbed by police as she and a group of protesters tried to block a key commuter bridge in Montreal last month.
Francoise David, who is co-leader of Quebec solidaire with Khadir, said in a telephone interview she is proud of Khadir's social activism but decried the police action.
She said she has participated in student demonstrations in several cities, including Montreal, in the same way and not had any problems. David said police in those circumstances had the wisdom to let the marches continue as long as they were peaceful.
"Why did the Quebec City police decide it was necessary to interrupt a peaceful march and give tickets, as I understand it, for violating the highway code?" she asked. "It's completely ridiculous. They have better things to do."
David pointed out it's normal for people to express their dissatisfaction and they should be allowed to do it as long as they're peaceful. She said she hoped Khadir's arrest and that of a student negotiator a few weeks ago as he left a negotiating session with the government would give police pause for thought.
"I hope there will be some reflection in certain police forces because this type of arrest is truly arbitrary and completely useless."
The mass arrests in Quebec City were a contrast to the evening's march in Montreal, where people have taken to the streets for 43 nights in a row.
Where some of the marchers have previously numbered in the thousands, barely a few hundred people showed up Tuesday night as rain fell on Montreal.
They marched around the city's downtown, clanking on pots and pans, which has become a favoured method of protest in recent weeks.
The march was mainly peaceful although some marchers and police appeared to get into verbal disputes. Montreal police did not make any arrests.
Earlier in the day, Montreal Mayor Gerald Tremblay met with the leader of one student federation to express his concern about the effect of daily demonstrations on the city's economy, especially as the Grand Prix race gets underway this week and festivals such as the Just For Laughs comedy festival and the Jazz Festival are about to kick off.
Martine Desjardins, leader of the Quebec university students federation, said the meeting was cordial but that students would continue demonstrating. She added she hoped there would be a successfully negotiated end to the crisis.
The mood was somewhat more lighthearted during another news conference where one protester insisted he couldn't bear Montreal's anti-mask bylaw anymore.
The Anarchopanda —a person in a full panda suit and the unofficial mascot of the Montreal protest — appeared outside the provincial courthouse with his lawyers and announced he would challenge the bylaw in Quebec Superior Court, saying it is unjust and unconstitutional.
The bylaw, passed May 18, forbids the wearing of masks during public protests and requires demonstrators to provide march routes to police.
The Anarchopanda is one of many costumed characters that show up at the marches. Others include a man dressed as the cartoon dog Scooby Doo and a man wearing a full squirrel costume.
Both Montreal and Quebec City protests also have demonstrators dressed as bananas, who have been dubbed Banarchists.
— By Nelson Wyatt and Martin Leblanc in Montreal