Siobhan McCrohan began the defence of her title in style as she was a convincing winner of her heat at the Rowing World Championships in Canada.The Galway woman won gold at the world championships in Belgrade last year and is looking to make it back-to-back titles in the lightweight single sculls competition.McCrohan finally got her campaign underway on Tuesday following delays at the Canada event, and finished first in heat three, five and a half seconds ahead of Mexico's Kenia Lechuga Alanis and nine seconds ahead of third placed Martyna Radosz from Poland.Her impressive time of 8:23.03 was the quickest time from all four heats, over three seconds faster than Zoi Fitsiou of Greece and Romania's Ionela Livia Cozmiuc who won heats two and four respectively.McCrohan will race the semi-final on Friday, while Paul O'Donovan will go in the men's equivalent on the same day with both hoping to qualify for Saturday's final.The week-long event in Canada is for non-Olympic or Paralympic categories following the recent culmination of the Paris Games.