Hello,
In general, you only need to declare world wide income if you have residential ties to Canada. You can find out more here: http://www.cra-arc.gc.ca/tx/nnrsdnts/ndvdls/nwcmr-eng.html#b.
Also, see here for more information on who needs to file a return: http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/flng-blgtns/menu-eng.html