The Opposition Parti Québécois retained two ridings in byelections Monday as its leader Jean-François Lisée passed his first major test since becoming leader of the sovereigntist party two months ago.

The governing Liberals won their Montreal stronghold of Verdun but saw their share of the popular vote drop in all four byelections when compared with their performances in 2014.

One of the PQ victories came in Saint-Jérôme, which had been vacant since former leader Pierre Karl Péladeau left politics last May.

Marc Bourcier had more than 45 per cent of the vote for the PQ, compared to the 36.8 per cent garnered by Péladeau in the 2014 election.

The PQ also kept its stronghold of Marie-Victorin, a South Shore riding last represented by the party's ex-house leader, Bernard Drainville.

Catherine Fournier had more than 50 per cent of the vote, outdistancing Drainville's 38.2 per cent from two years ago.

"What a beautiful evening," Lisée said, pointing out Fournier, at 24, will become the youngest woman ever elected to the National Assembly.

Catherine Fournier, who won in the riding of Marie-Victorin, will become the youngest woman ever elected to the national assembly at the age of 24. (Radio-Canada) "The citizens of Marie-Victorin ... sent a clear message to the Liberal government, which is the most toxic government in our recent history. Their austerity program is unacceptable," Fornier said.

Liberals see drop in popular vote but take Verdun

Isabelle Melançon won Verdun for the Liberals with about 35 per cent of the popular vote, a significant drop from Jacques Daoust's 50.6 per cent from two years ago.

Premier Philippe Couillard stood beside Melançon in Verdun and thanked volunteers and the candidates in the three other ridings.

New Quebec Liberal MNA Isabelle Melançon celebrates with Premier Philippe Couillard after winning the riding of Verdun in a provincial byelection. (Graham Hughes/Canadian Press) "Of course we would have preferred different results but there will be other battles," he said. "We will continue our work. Our priorities remain the same: education; health, particularly the elderly; and of course jobs and the economy."

CAQ keeps Arthabaska

The fourth byelection of the night saw Éric Lefebvre of the Coalition Avenir Québec easily win Arthabaska, which had been vacant since Sylvie Roy's death earlier this year.

Roy won the riding for the CAQ with a hefty majority in 2014 before she became an Independent a year later.

The Coalition Avenir Québec's Éric Lefebvre speaks at his victory party. The CAQ easily won Arthabaska, which had been vacant since Sylvie Roy's death earlier this year. (Radio-Canada) An emotional Lefebvre thanked all those who voted for him at his victory party, vowing to champion causes of importance to the region.

The results will have little impact on the standings in the 125-member legislature. The Liberals have 70 seats, the PQ 30 and the CAQ 21. There are also three Quebec solidaire members and one Independent.

The next general election is set for the fall of 2018.