TORONTO (Reuters) - The Toronto Stock Exchange’s main index ended lower Monday as energy issues slid along with oil prices and investors shrugged off a boost in merger activity, including a multibillion-dollar offer for Novelis by India’s top aluminium producer.The S&P/TSX composite index closed down 43.41 points, or 0.3 percent, at 13,040.54.

Six of the index’s 10 main groups were lower, led by a 1.1 percent slide in the heavyweight energy sector, which accounts for nearly 30 percent of the index’s weighting.

“With the market hitting new highs you have people looking to take it as an opportunity to trim positions somewhat,” said Paul Taylor, chief investment officer at BMO Harris Investment Management Inc.

“I don’t think there’s a big, significant move in any one direction or the other in particular, but more of a little bit of malaise as we get into some better economic data that will tell us whether, in fact, the commodities prices are going to continue to drift moderately lower.”

Energy issues slid with the price for US crude oil, which dropped nearly 3.5 percent to $57.81 a barrel after a Saudi oil minister said OPEC might leave output levels unchanged when it meets next month.

EnCana Corporation dropped 91 Canadian cents, or 1.6 percent, to C$56.09, while Talisman Energy shed 26 Canadian cents, or 1.3 percent, to C$19.99.

The resource-laden materials group fell 0.2 percent amid weakness in some underlying commodities.

Barrick Gold Corp. lost 43 Canadian cents, or 1.2 percent, to C$35.64.

Shares of Novelis jumped C$6.26, or 13.9 percent, to C$51.33 after Hindalco Industries said it would acquire the Alcan spinoff.

Hindalco will pay $3.5 billion and take on debt of $2.4 billion under the agreement.

Other merger news included a C$251 million offer for small financial services firm Rockwater Capital by CI Financial Income Fund.

CI units rose 20 Canadian cents, or 0.8 percent, to C$26.30 while Rockwater climbed 18 Canadian cents, or 2.4 percent, to C$7.58.